Literature Cited
Aber, J., Nielson, R.P., Lenihan, J.M., Bachelet, D., Drapek, R.J. 2001. Forest
processes and global environmental change: Predicting the effects of
individual and multiple stressors. Bioscience 51: 735-751.
This paper addresses the predicted impact of increased temperature and other
stressors on the distribution, condition, species composition, and productivity of
forests. Increases in temperature have lengthened the growing season in
temperate systems and have increased growth responses in boreal forests.
Climate change is expected to boost overall forest productivity by more than 20%
in the U.S.
Abstract: We review the effects of several rapidly changing environmental
drivers on ecosystem function, discuss interactions among them, and summarize
predicted changes in productivity, carbon storage, and water balance.
Adams, H.D, Kolb, T.E. 2004. Drought responses of conifers in ecotone
forests of northern Arizona: tree ring growth and leaf δ13C. Oecologia 140:
217-225.
This study analyses growth response in conifers in response to drought. The
researchers used two approaches that provide different information about
drought response: the ratio of standardized radial growth in wet years to dry
years (W:D) for the period between years 1950 and 2000 as a measure of growth
response to drought, and 13C in leaves formed in non-drought (2001) and
drought (2002) years as a measure of change in water use efficiency (WUE) in
response to drought. Low elevation populations of P. ponderosa had greater
growth response to drought than high-elevation populations. Increases in WUE in
response to drought were similar for all species at the ponderosa pine/mixed
conifer ecotone.
Adams AS, Six DL .2006. Temporal variation in mycophagy and prevalence
of fungi associated with developmental stages of the mountain pine beetle,
Dendroctonus ponderosae (Coleoptera: Scolytinae, Curculionidae).
Environmental Entomology 36: 64-72
This paper discusses the potential temporal shift in the relationship between D.
ponderosae and its fungal symbionts driven by climate change. G. clavigera, a
fungal symbiont of D. ponderosae, was most likely to be found in phloem
adjacent to prewintering third- and postwintering fourth-instar larvae. O. montium
was most likely to be found in phloem adjacent to eggs, first-instar larvae, pupae,
and teneral adults. Results suggest that not only are D. ponderosae broods in
contact with and feeding on fungi throughout development, but also, that during
development, contact of brood with a particular fungus is likely to change. Such
temporal shifts in fungal symbionts may be environmentally driven and have
important implications in how fungi interact with their hosts within and across
generations.
Alfaro, R.I.; Campbell, R.; Vera, P.; Hawkes, B.; Shore, T. 2004.
Dendroecological
reconstruction of mountain pine beetle outbreaks in the Chilcotin Plateau
of British
Columbia. Pages 245-256 in T.L. Shore, J.E. Brooks and J.E. Stone, eds.
Challenges and
Solutions: Proceedings of the Mountain Pine Beetle Symposium. Kelowna,
British Columbia. October 30-31, 2003. Natural Resources Canada,
Canadian Forest Service, Pacific Forestry Centre, Victoria, British
Columbia, Information Report BC-X-399. 298 p.
This study reconstructed recurrence rates for mountain pine beetle
(Dendroctonus ponderosae Hopk.) (Colyoptera: Scolytidae) outbreaks in British
Columbia and discusses conditions including climate that may impact stand
susceptibility. The mountain pine beetle periodically increases to outbreak levels,
killing thousands of trees. It is considered one of the major natural disturbance
agents in North America. Beetle outbreaks do not normally kill all the trees in a
stand, and the surviving trees experience extended periods of increased growth.
Mountain pine beetle generally attack stands that are more than 80 years old and
contain many large-diameter trees.
Allen, C.D. 2007. Cross-scale interactions among forest dieback, fire, and
erosion in northern New Mexico landscapes. Ecosystems 10:797-808.
This paper discusses the impact of predicted warmer temperatures and extreme
droughts on the interactions between vegetation dieback, grazing, and fire and its
impact on land surface properties, cross-scale hydrologic connectivities, and
alteration of ecohydrological patterns of runoff and erosion. The interaction
among disturbance processes exhibits a nonlinear relationship across spatial
scales. This can result in forest dieback among dominant species, an increased
risk of bark beetle outbreaks, and enhanced propagation of wildfires.
Abstract: Ecosystem patterns and disturbance processes at one spatial scale
often interact with processes at another scale, and the result of such cross-scale
interactions can be nonlinear dynamics with thresholds. Examples of cross-scale
pattern-process relationships and interactions among forest dieback, fire, and
erosion are illustrated from northern New Mexico (USA) landscapes, where longterm studies have recently documented all of these disturbance processes. For
example, environmental stress, operating on individual trees, can cause tree
death that is amplified by insect mortality agents to propagate to patch and then
landscape or even regional-scale forest dieback. Severe drought and unusual
warmth in the southwestern USA since the late 1990s apparently exceeded
species-specific physiological thresholds for multiple tree species, resulting in
substantial vegetation mortality across millions of hectares of woodlands and
forests in recent years. Predictions of forest dieback across spatial scales are
constrained by uncertainties associated with: limited knowledge of speciesspecific physiological thresholds; individual and site specific variation in these
mortality thresholds; and positive feedback loops between rapidly-responding
insect herbivore populations and their stressed plant hosts, sometimes resulting
in nonlinear ‘‘pest‘‘ outbreak dynamics. Fire behavior also exhibits nonlinearities
across spatial scales, illustrated by changes in historic fire regimes where patchscale grazing disturbance led to regional scale collapse of surface fire activity
and subsequent recent increases in the scale of extreme fire events in New
Mexico. Vegetation dieback interacts with fire activity by modifying fuel amounts
and configurations at multiple spatial scales. Runoff and erosion processes are
also subject to scale-dependent threshold behaviors, exemplified by
ecohydrological work in semiarid New Mexico watersheds showing how declines
in ground surface cover lead to non-linear increases in bare patch connectivity
and thereby accelerated runoff and erosion at hillslope and watershed scales.
Vegetation dieback, grazing, and fire can change land surface properties and
cross-scale hydrologic connectivities, directly altering ecohydrological patterns of
runoff and erosion. The interactions among disturbance processes across spatial
scales can be key drivers in ecosystem dynamics, as illustrated by these studies
of recent landscape changes in northern New Mexico. To better anticipate and
mitigate accelerating human impacts to the planetary ecosystem at all spatial
scales, improvements are needed in our conceptual and quantitative
understanding of cross-scale interactions among disturbance processes.
Allen, C.D., Breshears, D.D. 1998. Drought-induced shift of a forestwoodland ecotone: rapid landscape response to climate variation.
Proceedings of the National Academy of Sciences 95: 14839-14842.
This study documented the combined impact of severe drought, mortality from
bark beetles and land use policies on a rapid and substantial ecotone shift. At the
Bandelier Wilderness study site, drought induced mortality in ponderosa pine
was exacerbated by bark beetle infestations. This resulted in a shift in the
ponderosa pine forest and pinion-juniper woodland ecotone of greater than 2 km
in less than 5 years. Current models do not reflect the rapid pace of vegetation
shifts expected as a result of climate change.
Abstract: In coming decades, global climate changes are expected to produce
large shifts in vegetation distribution at unprecedented rates. These shifts are
expected to be most rapid and extreme at ecotones, the boundaries between
ecosystems, particularly those in semiarid landscapes. However, current models
do not adequately provide for such rapid effects – particularly those caused by
mortality – largely because of the lack of data from field studies. Here we report
the most rapid landscape-scale shift of a woody ecotone ever documented: in
northern New Mexico in the 1950s, the ecotone between semiarid ponderosa
pine forest and pinion-juniper woodland shifted extensively (2 km or more) and
rapidly (<5 years) through mortality of ponderosa pines in response to severe
drought. This shift has persisted for 40 years. Forest patches within the shift zone
became much more fragmented, and soil erosion greatly accelerated. The
rapidity and the complex dynamics of the persistent shift point to the need to
represent more accurately these dynamics, especially the mortality factor, in
assessments of the effects of climate change.
Allen, J.L., Wesser, S., Markon, C.J., Winterberger, K.C. 2006. Stand and
landscape level effects of a major outbreak of spruce beetles on forest
vegetation in the Copper River Basin, Alaska. Forest Ecology and
Management 227: 257–266.
This study examined the stand and landscape level effects of a spruce beetle
outbreak on forest vegetation structure and composition in the Copper River
Basin, Alaska. Spruce beetles selectively attack medium to large white spruce
trees. High levels of infestation can severely alter stand dynamics leading to a
homogenization of tree age and species, or a change in community composition.
Abstract: From 1989 to 2003, a widespread outbreak of spruce beetles
(Dendroctonus rufipennis) in the Copper River Basin, Alaska, infested over
275,000 ha of forests in the region. During 1997 and 1998, we measured forest
vegetation structure and composition on one hundred and thirty-six
20-m x 20-m plots to assess both the immediate stand and landscape level
effects of the spruce beetle infestation. A photo-interpreted vegetation and
infestation map was produced using color-infrared aerial photography at a scale
of 1:40,000.We used linear regression to quantify the effects of the outbreak on
forest structure and composition. White spruce (Picea glauca) canopy cover and
basal area of medium-to-large trees ≥15 cm diameter-at-breast height (1.3 m,
dbh)] were reduced linearly as the number of trees attacked by spruce beetles
increased. Black spruce (Picea mariana) and small diameter white spruce (<15
cm dbh) were infrequently attacked and killed by spruce beetles. This selective
attack of mature white spruce reduced structural complexity of stands to earlier
stages of succession and caused mixed tree species stands to lose their white
spruce and become more homogeneous in overstory composition. Using the
resulting regressions, we developed a transition matrix to describe changes in
vegetation types under varying levels of spruce beetle infestations, and applied
the model to the vegetation map. Prior to the outbreak, our study area was
composed primarily of stands of mixed white and black spruce (29% of area) and
pure white spruce (25%). However, the selective attack on white spruce caused
many of these stands to transition to black spruce dominated stands (73%
increase in area) or shrublands (26% increase in area). The post-infestation
landscape was thereby composed of more even distributions of shrubland and
white, black, and mixed spruce communities (17–22% of study area). Changes in
the cover and composition of understory vegetation were less evident in this
study. However, stands with the highest mortality due to spruce beetles had the
lowest densities of white spruce seedlings suggesting a longer forest
regeneration time without an increase in seedling germination, growth, or
survival.
Amman, G.D. 1977. The role of mountain pine beetle in lodgepole pine
ecosystems: Impact on succession. Pgs. 3–18, In: Mattson, W.J. (ed.),
Proceedings in the Life Sciences-Arthropods in Forest Ecosystems,
Springer-Verlag, New York.
This study documented the effects of mountain pine beetle infestation on three
lodgepole pine forests at different successionary levels. The influence of
mountain pine beetle on succession of lodgepole pine stands depends on the
successional status at the time of outbreak with many stands persisting long
enough for a number of beetle infestations to occur. Outbreaks which target large
diameter trees occur at 20-40 year intervals often resulting in two- or three-story
stands consisting of trees of different ages and sizes.
Abstract: The mountain pine beetle, Dendroctonus ponderosae (Coleoptera:
Scolytidae), is the most aggressive member of its genus in the western United
States. Populations of the beetle periodically build up and kill most of the large
dominant lodge pole pines, Pinus contorta var. latifolia over vast acreages. The
beetle is indigenous to North America and probably has been active in lodge pole
pine ecosystems almost as long as lodge pole pine has existed. Frequency of
infestations in a given area of forest appears to range from about 20 to 40 years,
depending upon how rapidly some trees in the stand grow to large diameter and
produce thick phloem, conditions conducive to buildup of beetle populations. In
addition, trees must be at a latitude and elevation where temperatures are
favorable for beetle development.
Amman, G.D., McGregor, M.D., Cahill, D.B., Klein, W.H. 1977. Guidelines
For reducing losses of lodgepole pine to the mountain pine beetle in
unmanaged stands in the Rocky Mountains. GTR-INT-36. USDA Forest
Service, Intermountain Research Station, Ogden, UT, 19 pp.
This report describes the habits and habitat of the mountain pine beetle and
presents methods for land managers to reduce bark beetle related losses in
managed stands and for high value trees. The mountain pine beetle shows a
strong preference for lodgepole pine of large diameter and 80 years of age or
older. The cool climate of high elevations has an adverse effect on brood
development and survival. These factors – tree diameter, tree age, and stand
location -- are used to predict stand risk to beetle infestation.
Abstract: These guidelines are based on ecological relationships of the beetle
and its host. They are applicable to unmanaged stands. In the stands, beetles
show a strong preference for lodgepole pine of large diameter and 80 years of
age and older. Stands at low elevations suffer the greatest losses to beetle
infestation. At low elevations, climate is optimal for brood survival; the cool
climate of high elevations has an adverse effect on survival of the beetle. These
factors—tree diameter, tree age, and stand location—are used to predict stand
risk to beetle infestation. Measures can be taken to prevent or reduce losses to
the beetle. Where timber production is the primary use of the land, large high risk
trees can be removed by partial cutting techniques. However, patch cutting or
clear cutting should be used where most trees are in large-diameter classes and
in stands where residual trees would not be numerically adequate nor physically
vigorous should partial cutting techniques be used. Essentially a “do nothing”
policy recommended where recreation values predominate or where
noncommercial forests exist. Trees of high value in campgrounds, picnic areas,
and near summer and permanent homesites can be protected with chemical
sprays that prevent successful beetle infestation.
Asshoff, R., Zotz, G., Körner, C. 2006. Growth and phenology of mature
temperate forest trees in elevated CO2. Global Change Biology 12: 848-861.
This study chronicled the effects of CO2 enrichment in six species of deciduous
trees during 4 years of Free Air CO2 Enrichment (FACE) experiments. The
observations do not support the notion that mature forest trees will accrete wood
biomass at faster rates in a CO2-enriched atmosphere but may indicate some
mitigation of drought effects. Even if mature trees accreted more biomass carbon
in trunks in response to elevated CO2, such stimulation would simply accelerate
the trees’ life cycle and not necessarily enhance long-term C pools.
Ayres, M.P., Lombardero. M.J. 2000. Assessing the consequences of global
change for forest disturbance from herbivores and pathogens. Science of
the total environment 262: 363-286.
This paper discusses the current impacts of herbivores and pathogens on forest
community and stand structure as well as the potential range shifts and changes
in community composition as a result of climate change. Increases in summer
temperatures can result in elevational and latitudinal range shifts while increases
in winter temperatures will increase brood survival. These factors can lead to
bark beetle outbreaks that alter the species composition and structure of the
forest affecting evapotranspiration, CO2 flux, and heat transfer.
Baker, W.L., Veblen, T.T. 1990. Spruce Beetles and Fires in the NineteenthCentury Subalpine Forests of Western Colorado, U.S.A. Arctic and Alpine
Research, 22(1): 65-80.
This study used historic photographs to reconstruct patterns of spruce beetle
caused mortality and fires and their impact on forest succession and species
composition. Bark beetle disturbances can dictate forest distribution, abundance,
age and size of trees in a similar manner to fire. Often where a fire destroys
young understory trees, bark beetle outbreaks preferentially cause mortality in
older trees and allow for the sudden growth of understory trees when canopy
space becomes available.
Balanyá, J., Oller, J.M., Huey, R.B., Gilchrist, G.W., Serra, L. 2006. Global
Genetic Change Tracks Global Climate Warming in Drosophila subobscura.
Science 313: 1773 – 1775.
This paper studied the genetic impact of global warming on the fly Drosophila
subobscura. The frequency of chromosome inversions associated with warm
latitudes have increased with increasing temperature on all three continents
where the fly is found. This rapid genetic shift is detectable even in samples
separated by fewer than two decades and has been recently observed in other
insects as well, although on more limited geographic scales.
Bale, J.S., Masters, G.J., Hodkinson, I.D., Awmack, C., Bezemer, T.M.,.
Brown, V.K., Butterfield, J., Buse, A., Coulson, J.C., Farrar, J., Good, J.E.G.,
Harrington, R., Hartley, S., Jones, T.H., Lindroth, R.L., Press, M.C.,
Symrnioudis, I., Watt, A.D., Whittaker, J.B. 2002. Herbivory in global
climate change research: direct effects of rising temperature on insect
herbivores. Global Change Biology 8 (1): 1–16.
This paper discusses the insect/plant life-history strategies and the potential
impacts warming temperatures on development rates, voltinism, and host
availability. The diversity of insect species tends to decrease with increasing
latitude and altitude. Climatic warming will allow temperate insect species to
extend their ranges to higher latitudes and altitudes. Many montane and coldadapted species with restricted climatic ranges are likely to be more vulnerable to
extinction.
Bale J.S., Walters, K.F.A. 2001. Overwintering biology as a guide to the
establishment potential of non-native arthropods in the UK. Animal
Developmental Ecology. BIOS Sci. Ltd, Oxford, UK.
This study focuses on the relationship between temperature and insect
developmental thresholds, voltinism, and survival. The low temperature mortality
of insects is a function of both the temperature and the duration of exposure.
Overwinter survival is determined by the severity of the cold stress experienced
in winter and the cold tolerance of individual insects. Two survival strategies that
are employed by overwintering insects are freeze tolerance and freeze
avoidance.
Barber, V.A., Juday, G.P. Finney, B.P. 2000. Reduced growth of Alaskan
white spruce in the twentieth century from temperature-induced drought
stress. Nature 405: 668-673.
This study examined tree-ring records from the past 90 years which strongly
indicate that radial growth has decreased with increasing temperature.
Temperature-induced drought stress has disproportionately affected the most
rapidly growing white spruce, suggesting that, under recent climate warming,
drought may have been an important factor limiting carbon uptake in North
American boreal forests. An increase in the length of the growing season along
with warmer summer temperatures could deplete already limited soil moisture.
Battisti, A., Stastny, M., Buffo, E., Larsson, S. 2006. A rapid altitudinal range
expansion in the pine processionary moth produced by the 2003 climatic
anomaly. Global Change Biology 12: 662–671.
This paper studied the effects of recent climate change on flight periodicity and
distance in the winter pine processionary moth (Thaumetopoea pityocampa). The
pine processionary moth is an important pine defoliator whose larvae feed in
colonies during the winter, and is limited in its distribution by winter temperatures.
In the last three decades, warmer winters have led to a gradual but substantial
expansion of its range both latitudinally and altitudinally. The summer of 2003
has facilitated unprecedented colonization outside the range limit due to the
highest summer temperatures in Europe over the past 500 years.
Bazzaz, F.A., Chiariello, N.R., Coley, P.D.. Pitelka, L.F. 1987 Allocating
Resources to Reproduction and Defense. In How Plants Cope: Plant
Physiological Ecology. BioScience 37 (1): 58-67.
This study examined the variation in resource allocation which occurs through
differences in the chemical composition of structures, the relative mass of
different structures or organs, and the relative number of different structures a
plant produces. This variation occurs within individuals through time, within and
among populations, and especially among species. Examinations of this variation
cross many fields of ecology, including physiological studies of the relationship
between structure and function in plants, biochemical studies of coevolutionary
diversification in plant defense, and theoretical studies of life history evolution.
Bentz, B.J., Mullins, D.E. 1999. Ecology of mountain pine beetle
(Colyoptera: Scolytidae) cold hardening in the Intermountain West.
Environmental Entomology 28:577–587.
This study assessed supercooling points of field collected mountain pine beetle
larvae, the physiological mechanisms that allow cold tolerance in mountain pine
beetle larval stages, and characterized the pattern of low temperature tolerance
among geographic regions. Differences in cold hardening are impacted by
minimum phloem temperatures which were not significantly different between
north and south aspects. There was 100% mortality in larvae exposed to
temperatures at or below the super cooling point indicating that mountain pine
beetle larvae are freeze intolerant.
Abstract: The mountain pine beetle, Dendroctonus ponderosae Hopkins, spends
the majority of its life cycle within the phloem of pine trees, experiencing
exposure to temperatures below −30°C in many parts of their expansive range.
To better understand cold tolerance capabilities of this insect, seasonal patterns
of cold-hardiness, as measured by supercooling points in the laboratory, were
compared with seasonal patterns of host tree phloem temperatures at several
geographic sites for 2 beetle generations. Larvae were found to be intolerant of
tissue freezing, and supercooling points measured appear to be a reasonable
estimate of the lower limit for survival. Of the compounds analyzed, glycerol was
found to be the major crynoprotectant. No differences in supercooling points
were found among instars or between larvae collected from the north and south
aspect of tree boles. Both phloem temperatures and supercooling points of
larvae collected from within the phloem were found to be different among the
geographic sites sampled. Mountain pine beetle larvae appear to respond to
seasonal and yearly fluctuations in microhabitat temperatures by adjusting levels
of cold hardening.
Bentz, B.J., Amman, G.D., Logan, J.A. 1993. A critical assessment of risk
classification systems for the mountain pine beetle. Forest Ecology and
Management 61(3-4): 349-366.
This study evaluated several mountain pine beetle hazard/risk systems for their
ability to predict mountain pine beetle caused mortality in forests in northern
Montana. Sustained outbreaks are dependent on factors related to stand
composition such as density, size distribution, phloem thickness and age of
individual trees. Accounting for temperature, which impacts bark beetle
development, and the effects of weather patterns may enhance the predictability
of mountain pine beetle population trends.
Abstract: Hazard/risk systems developed for mountain pine beetle management
traditionally have attempted to describe the potential for timber loss in pine
stands due to outbreak phase populations. A variety of stand and site
characteristics, as well as climatic conditions, have been used. In this study, four
hazard/risk systems were evaluated using data from 105 stands in northern
Montana. None of the systems evaluated were found to predict adequately
mountain pine beetle induced mortality which occurred in the test stands.
Possible reasons for the lack of predictive ability of these systems include: (1)
confusion in terminology used in hazard/risk rating for mountain pine beetle; (2)
lack of consideration of the mountain pine beetle population phase (e.g. endemic
or epidemic) during rating system development; (3) the need to include more
information concerning mountain pine beetle population dynamics; (4) the need
for inclusion of the spatial nature of both beetle populations and stand conditions.
Bentz, B.J., Logan, J.A., Amman, G.D. 1991. Temperature-dependent
development of the mountain pine beetle (Coleoptera: Scolytidae) and
simulation of its phenology. The Canadian Entomologist 123: 1083–1094.
This study used constant temperature rearing experiments at all developmental
stages to develop a temperature dependent phenology model that simulates
mountain pine beetle development. Temporally synchronized eclosion
encourages en masse attack, thus enabling beetles to overcome the defenses of
larger diameter host trees which provide more food for the developing brood
possibly leading to an epidemic population. Synchrony in development is
accomplished when temperatures become too cool for later instars to develop
allowing eggs and first- and second-instar larvae to coninue development at
lower thresholds.
Abstract: Temperature-dependent development of the egg, larval, and pupal lifestages of the mountain pine beetle (Dendroctonus ponderosae Hopkins) was
described using data from constant-temperature laboratory experiments. A
phenology model describing the effect of temperature on the temporal distribution
of the life-stages was developed using these data. Phloem temperatures were
recorded in a beetle infested lodgepole pine (Pinus contorta Douglas) were used
as input to run the model. Results from model simulations suggest that inherent
temperature thresholds in each life-stage help to synchronize population
dynamics with seasonal climatic changes. This basic phonological information
and the developed model will facilitate both research and management
endeavors aimed at reducing losses in lodgepole pine stands caused by
mountain pine beetle infestations.
Bentz, B.J., Logan, J.A., VandyGriff, J.C. 2001. Latitudinal variation in
Dendroctonus ponderosae (Coleoptera: Scolytidae) development time and
adult size. Canadian Entomologist 133 (3): 375-387.
This was a laboratory study of two populations of D. ponderosae one from Idaho
and one from Utah to determine if heritable differences exist in development time
or in adult size when reared under identical conditions. Local selection pressures
and latitudinal region are primary determinants of D. ponderosae adult size and
development time. Brood host was not found to be significant in explaining
observed differences in adult size. Development time and adult size are heritable
traits and genotypes may be adapting to local thermal regimes along a latitudinal
gradient.
Abstract: Dendroctonus ponderosae (Hopkins) is widely distributed across
western North America, feeding in at least 12 native species of Pinus L.
(Pinaceae). We investigated the existence of heritable differences in two lifehistory parameters (adult size and development time) of D. ponderosae from a
northern population (central Idaho, Pinus contorta Douglas ex Loudon) and a
southern population (southern Utah, Pinus ponderosa Douglas ex P. and C.
Lawson). We attempted to separate heritable from environmental effects by
rearing individuals from both populations through two generations (F1 and F2) in a
common standardized laboratory environment with a constant temperature. Two
treatment effects were tested for in the F2 generation: (1) geographic location
(source host) for F0 D. ponderosae; and (2) the F2 brood host. We hypothesized
that. If differences were observed and the F0 source host and region had a
greater effect on F2 brood development time and adult size than did the host in
which F2 brood were reared, a heritable factor related to the F0 parents was
responsible. Time to emergence was significantly shorter for second-generation
offspring in the northern population than for second-generation offspring in the
southern population, regardless of the F2 brood host. Although both the F2 brood
host and F0 source parents were significant in explaining differences observed in
the development-time distribution of F2 brood, the F0 source effect was found to
be much greater. Also F2 males and females from southern source parents were
significantly larger than F2 brood from northern source parents when reared in
both F2 brood hosts. Geographic region and original host of F0 source parents
had a significant effect on F2 offspring size, whereas the immediate food for F2
brood was not significant in explaining differences. These results suggest
genetically based regional differences in D. ponderosae populations.
Bentz, B.J. and D.L. Six. 2006. Ergosterol content of fungi associated with
Dendroctonus ponderosae and D. rufipennis (Coleoptera: Curculionidae,
Scolytinae). Annals of the Entomological Society of America 99(2):189-194.
This paper studied the impact of the fungi L. abietum, O. montium and O.
clavigerum on the brood success of two bark beetles D. ponderosae and D.
rufipennis. Fungal feeding may provide vital nutrients either non-existent or found
in inadequate levels in woody plant tissues and may also provide an alternate
source of sterols typically found in low concentrations or in forms unusable by
insects. Leptographium abietum is found on the pronota and elytra of D.
rufipennis and both Ophiostoma montium and Ophiostoma clavigerum are found
on the maxillae in sac mycangia of D. ponderosae.
Abstract: Insects require sterols for normal growth, metamorphosis, and
reproduction, yet they are unable to synthesize these organic compounds and
are therefore dependent upon a dietary source. For phloephagous species, such
as Dendroctonus bark beetles, whose food does not necessarily contain
appropriate types or adequate quantities of sterols, fungal symbionts may
provide an alternative source in the form of ergosterol. We determined and
compared the relative amounts of ergosterol in the primary fungal associates of
Dendroctonus ponderosae Hopkins and Dendroctonus rufipennis Kirby.
Ergosterol content of host tree phloem naturally infested with larvae (and their
fungal symbionts) of both species also was compared with ergosterol contents in
uninfested phloem tissue. Mycelia of Ophiostoma montium (Rumfold) von Arx
and Ophiostoma clavigerum (Robinson-Jeffrey & Davidson) Harrington isolated
from D. ponderosae mycangia, and Leptographium abietinum (Peck) Wingfield
isolated from the exoskeleton of D. ruifpennis contained relatively large quantities
of ergosterol, although no significant differences in content were found among
these fungal species. Phloem colonized by larvae of both species contained
significantly more ergosterol than did uninfested host phloem tissue. Our results
suggest that larval life stages of D. ponderosae and D. rufipennis may obtain vital
nutrients not only from the host tree phloem but also from fungal symbionts, in
the form of ergosterol, while mining larval galleries.
Bentz, B.J., M. Pfrender, R. Bracewell, and K. Mock. 2007. Genetic
architecture of differences in fitness traits among geographically separated
Dendroctonus ponderosae populations. In Bentz, Cognato, Raffa (eds),
Proceedings from the Third Workshop on Genetics of Bark Beetles and
Associated Microorganisms. USDA For. Serv. Proceedings RMRS-P-45.
This study examined additive and nonadditive genetic traits in three
geographically separated populations of Dendroctonus panderosae reared under
laboratory conditions. Mean development time for all populations was slower
and adults were larger at cold rearing temperatures when compared to warm
temperatures. Results suggest that selection plays a role in MPB adaptation to
temperature and to local environments that could lead to geographically specific
voltinism patterns under a global warming scenario.
Abstract: The mountain pine beetle, Dendroctonus ponderosae Hopkins
(Coleoptera: Curculionidae, Scolytinae) (MPB), is widely distributed across
western North America spanning 25 degrees latitude and more than 2,500 m
elevation. In a common garden experiment, Bentz and others (2001) observed
that MPB populations from a southern location required significantly more time to
develop than individuals from a population in the northern part of the range,
although both populations exhibited univoltinism. Adults from the southern
population were also significantly larger, even when reared in a common host
and temperature. These results suggest that local selection plays a role in MPB
adaptation to temperature, which can vary dramatically across the broad range of
MPB. In a recent phylogeographic analyses of MPB, Mock and others (2007)
found evidence of genetic structuring among populations that followed a broad
isolation-by-distance pattern, confirming that genetic differences exist among
geographically isolated populations. Little is known, however, about the
underlying genetic architecture of important MPB life history traits, such as
development time. To adequately forecast the effects of climate change on MPB
population success and adaptability, a better understanding of the underlying
environmental and genetic control of these traits, and variability across
geographically separated populations, is needed. The main objective of our study
was to examine the genetic architecture of differences among three
geographically separated populations of MPB that differ in total development time
and adult size. We used line cross experiments to analyze the relative influences
of additive and nonadditive genetic effects on population differences in these
traits.
Berg, E.E., Henry, J.D., Fastie, C.L., De Volder, A.D., Matsuoka. S.M. 2006.
Spruce beetle outbreaks on the Kenai Peninsula, Alaska, and Kluane
National Park and reserve, Yukon Territory: Relationship to summer
temperatures and regional differences in disturbance regimes. Forest
Ecology and Management 227: 219-232.
This study used core samples and historical records to reconstruct drought
related spruce beetle outbreaks and subsequent growth release in surviving
trees. On the Southern Kenai Peninsula, the sustained onset of warm summers
beginning in 1987 was followed by substantial increase in red needle mortality in
spruce beginning in 1990 and climaxing in 1996. In the Kluane region, higher
than average temperatures beginning in 1989 were associated with the outbreak
that continued through 2005. Increases in the rate of spruce beetle reproduction
and trees stressed by 5–6 years of drought likely resulted in spruce beetle
outbreaks.
Abstract: When spruce beetles (Dendroctonus rufipennis) thin a forest canopy,
surviving trees grow more rapidly for decades until the canopy closes and growth
is suppressed through competition. We used measurements of tree rings to
detect such growth releases and reconstruct the history of spruce beetle
outbreaks at 23 mature spruce (Picea spp.) forests on and near the Kenai
Peninsula, Alaska and four mature white spruce (Picea glauca) forests in Kluane
National Park and Reserve, Yukon Territory. On the Kenai Peninsula, all stands
showed evidence of 1–5 thinning events with thinning occurring across several
stands during the 1810s, 1850s, 1870–1880s, 1910s, and 1970–1980s, which we
interpreted as regional spruce beetle outbreaks. However, in the Kluane region
we only found evidence of substantial thinning in one stand from 1934 to 1942
and thinning was only detected across stands during this same time period. Over
the last 250 years, spruce beetle outbreaks therefore occurred commonly among
spruce forests on the Kenai Peninsula, at a mean return interval of 52 years, and
rarely among spruce forests in the Kluane region where cold winter temperatures
and fire appear to more strongly regulate spruce beetle population size. The
massive 1990s outbreaks witnessed in both regions appeared to be related to
extremely high summer temperatures. Recent outbreaks on the Kenai Peninsula
(1971–1996) were positively associated with the 5-year backwards running
average of summer temperature. We suggest that warm temperature influences
spruce beetle population size through a combination of increased overwinter
survival, a doubling of the maturation rate from 2 years to 1 year, and regional
drought-induced stress of mature host trees. However, this relationship
decoupled after 1996, presumably because spruce beetles had killed most of the
susceptible mature spruce in the region. Thus sufficient numbers of mature
spruce are needed in order for warm summer temperatures to trigger outbreaks
on a regional scale. Following the sequential and large outbreaks of the 1850s,
1870–1880s, and 1910s, spruce beetle outbreaks did not occur widely again until
the 1970s. This suggests that it may take decades before spruce forests on the
Kenai Peninsula mature following the 1990s outbreak and again become
susceptible to another large spruce beetle outbreak. However, if the recent
warming trend continues, endemic levels of spruce beetles will likely be high
enough to perennially thin the forests as soon as the trees reach susceptible
size.
Berryman, A.A. and R.W. Stark. 1962. Studies on the effects of temperature
on the development of Ips confusus using radiographic techniques.
Ecology 43(4):722-726.
This study employed low kilovoltage X-rays to determine gallery construction,
egg laying and brood success at five different temperatures. The increase in the
activity of the parent adults was reflected in the developmental rates of the
resultant brood. The greatest numbers of Ips confusus progeny were produced at
20ºC with brood survival highest at 20ºC and 25ºC and the maximum rate of
brood development occurring between 30ºC to 35ºC.
Bigler, C., Kolakowski, D., Veblen.T.T. 2005. Multiple disturbance
interactions and drought influence fire severity in the Rocky Mountain
subalpine forests. Ecology 86: 3018-3029.
This paper discusses the relationship between drought, bark beetles, and
weather conditions and their impact on fire severity. Past disturbance by fire or
beetle outbreak strongly determines forest cover type and stand structure.
Following the decay of the fine fuels, overall fire hazard may actually decrease
for decades due to the increased moisture related to the development of mesic
understory vegetation in subalpine forests and lack of continuous fine fuel in the
canopy.
Biondi, F. Peter C. Hartsough, P.C., Estrada, I.G. 2005 Daily Weather and
Tree Growth at the Tropical Treeline of North America. Arctic, Antarctic,
and Alpine Research 37: 16–24.
This paper chronicled the environmental conditions during an outbreak of the
roundheaded pine beetle (Dendroctonus adjunctus Blandford) Increasing
temperatures in the spring initiated tree growth which continued as a result of
summer precipitation. It was possible to measure the decline of Pinus hartwegii
stem increment during the outbreak which ultimately killed most of the trees at
one of two experimental sites.
Bleiker K, Six DL. 2008. In press. Dietary benefits of fungal associates to an
eruptive herbivore: Potential implications of multiple associates on host
population dynamics. Environmental Entomology
This study examined the effects of fungal associates on the development and
success of mountain pine beetle broods which may supplement their diet
allowing them to develop in a nutritionally poor habitat at high densities. The
fungal associates of the mountain pine beetle may increase dietary nitrogen in
the phloem available to mid-to-late instars for feeding and increased phloem
nitrogen by 40% 8 weeks after attack. Total gallery area is greater for insects
developing on G. clavigera colonized or uncolonized phloem compared with
insects developing on treatment diets with O. montium present.
Boisvenue, C., Running, S.W. 2006. Impacts of climate change on natural
forest productivity–evidence since the middle of the 20th century. Global
Change Biology 12: 862-882.
This paper used satellite data as well as field data from carbon sequestration
research and forest management planning to review documented evidence of the
impacts of both long and short term climate change trends since the 1950s. The
response of forests to CO2, temperature, radiation, and precipitation will be
impacted by an increase in atmospheric O3. Productivity of temperate forests in
northwestern North America is limited by temperature in winter and spring, and
water in the summer.
Borden, J.H. 1997. Disruption of semiochemical-mediated aggregation in
bark beetles. Pgs. 421–438, In: Cardé, R.T., Minks A.K. (eds.), Insect
Pheromone Research: New Directions, Chapman and Hall, New York.
This paper studied the application methods used in dispersing multifunctional
and anti-aggregation pheromones and their effect on the bark beetle host
selection process. Pheromones such as MCH or verbenone are used in
conjunction with silvacultural practices such as pre-outbreak thinning and
removal of infested trees to protect individual stands and high value trees from
bark beetle attack. Aggregation pheromones are often deployed in traps outside
the protected area in a push-pull tactic intended to trasp dispersing beetles.
Botkin D.B., Saxe H., Araujo M.B., Betts R., Bradshaw R.H.W., Cedhagen T.,
Chesson P., Dawson T.P., Etterson J.R., Faith D.P., Ferrier S., Guisan A.,
Hansen A.S., Hilbert D.W., Loehle C., Margules C., New M., Sobel M.J.,
Stockwell D.R.B. Forecasting the effects of global warming on biodiversity.
Bioscience 57(3): 227-236.
This paper provides a framework for improving biodiversity forecasting by reexamining the parameters used by several models and integrating them into a
cohesive evaluation that includes species persistence and multiple causes of
biodiversity change. Species with the greatest genetic diversity are more likely to
undergo rapid evolution. There has already been a rapid genetic adaptation seen
in some wild organisms in long term field studies. This is also true in many
recently introduced invasive species.
Box, E.O. 1981. Predicting physiognomic vegetation types with climate
variables. Vegetation 45(2): 127-139.
This study details a new vegetation model which uses expanded classification of
vegetative life forms along with eight macroclimatic variables to predict future
vegetation formations. Climatic water balance and mean seasonal temperature
patterns are the primary determinants of plant form and vegetation structure.
Bradshaw, W.E. and C.M. Holzapfel. 2007. Evolutionary response to rapid
climate change. Science 312:1477-1478.
This paper discusses the evolutionary responses of several animals and insects
to longer and warmer growing seasons resulting from climate change. In recent
decades, heritable genetic changes attributed to climate change have occurred in
many animal populations including adaptation to the timing of seasonal events or
to season length. The rate of change varied by animal type ranging from
mosquitoes which showed clear change within five years to great tits in which
only a portion of the population has shown change after thirty years.
Breshears, D.D., Cobb, N.S., Rich, P.M., Price, K.P., Allen, C.D., Balice, R.G.,
Romme, W.H., Kastens, J.H., Floyd, M.L., Belnap, J., Anderson, J.J, Myers,
O.B., Meyer, C.W. 2005. Regional vegetation die-off in response to globalchange-type drought. Proceedings of the National Academy of Sciences
102: 15144-15148.
This study used the Normalized Difference Vegetation Index, aerial surveys, and
field inventories to evaluate the impact of a global climate change type drought
on regional scale pinon pine mortality. The four state regional study area
experienced drought combined with unusually high temperatures. A 17 year
period of increased precipitation preceding the recent drought allowed for rapid
tree growth. This resulted in increased stand densities, competition for water and
susceptibility to beetle attacks and pathogens. Tree mortality during this period
was greater than a previously recorded drought in the 1950s.
Brown, J.K. 1975. Fire cycles and community dynamics in lodgepole pine
forests. Pp. 430-456. In: Baumgarner, D.M. (ed), Proceedings, Symposium:
Management of Lodgepole Pine Ecosystems. Washington State
Cooperative Extension, Pullman, WA.
This study focuses on the relationship between stand structure, fire, and
succession in lodgepole pine forests. The type of fire impacts stand
characteristics such as density and rate of succession. The mountain pine beetle
has coevolved with lodgepole pine and its preference for colonizing larger trees
works against succession to climax stage in lodgepole pine forests.
Abstract: The influences of fire on succession, community diversity and stability,
expression of serotiny, stand establishment, development of stand structure, and
fuel accumulation are discussed for lodgepole pine forests. Fire, fuel
accumulation, and stand development interact in a complex biological network.
Mortality factors such as mountain pine beetle, suppression mortality, and fire
cause fuels to build up on the ground, creating varied fire intensity potentials.
Fires initiate a chain of biological events that affects the development of
lodgepole pine stands; in turn, the characteristics of stands affect their
susceptibility to mortality, fuel accumulation, and fire potential.
Callaway, R.M., DeLucia, E.H. 1994. Biomass allocation of montane and
desert ponderosa pine: An analog for response to climate change. Ecology
75: 1474-1481.
This study used cross sections taken at 1m intervals to determine if the biomass
allocation differed between montane and desert populations of P. ponderosae.
Large diameter desert P. ponderosa have larger sapwood volume: leaf area
ratios than montane P. ponderosa indicating a phenotypic acclimation or a
genotypic change has occurred in the desert populations. High biomass
allocation to sapwood may have many benefits including increased water and
carbohydrate storage capacities.
Cardoza, Y.J., Paskewitz, S. Raffa, K.F. 2006. Travelling through time and
space on wings of beetles: A tripartite insect-fungi-nematode association.
Symbiosis 41(2): 71-79.
This study examined the nematangia in both mountain pine and spruce beetles
and discovered the presence of nematodes and 15 microbial morphotypes. Bark
beetles have symbiotic relationships with many organisms including fungi,
bacteria, mites, and nematodes. All spruce beetle wings examined in our study
were covered with fungal spores and/or mycelia. Nematodes have variable
associations with bark beetles and may control fungi growth in brood galleries.
Carroll, A.L., Taylor S.W., Régnière J., Safranyik, L. 2004. Effects of Climate
Change on Range Expansion by the Mountain Pine Beetle in British
Columbia. Pages 223-232. in T.L. Shore, J.E. Brooks and J.E. Stone, eds.
Proceedings of the mountain pine beetle symposium: challenges and
solutions, October 30-31, 2003, Kelowna, British Columbia, Canada. Natural
Resources Canada, Canadian Forest Service, Pacific Forestry Centre,
Victoria, BC. Information Report BC-X-399. 298
This paper studied the impact of recent warming on the range expansion of the
mountain pine beetle in British Columbia followed by a decrease in overall bark
beetle infestations by the mid-1980s. Over time climate change will allow
mountain pine beetle to expand its range into formerly climatically hostile
environments. This is evident in small beetle populations persisting in the
northern Rockies where no beetle activity has been previously recorded.
Carroll, A.L., J. Regniere, J.A. Logan, S.W. Taylor, B.J. Bentz and J.A.
Powell. 2006. Impacts of climate change on range expansion by the
mountain pine beetle. Natural Resources Canada, MPBI P.O. #1.02, working
paper 2006-14. http://bookstore.cfs.nrcan.gc.ca/searchpubs_e.php.
This study addresses the increase in suitable habitat and range expansion of the
mountain pine beetle over the past thirty years and projects an increase in the
range of benign habitats under future climate change scenarios. Suitable habitat
for mountain pine beetle in south-central and south-eastern British Columbia has
increased 75% since 1970. Only climate change explains the increasing rate of
mountain pine beetle infestations. The Safranyik-Logan model predicts a
contiguous band of suitable Mountain pine beetle habitat across the boreal forest
by 2040.
Abstract: The current latitudinal and elevational range of mountain pine beetle
(MPB) is not limited by available hosts. Instead, its potential to expand north and
east has been restricted by climatic conditions unfavorable for brood
development. We combined a model of the impact of climatic conditions on the
establishment and persistence of MPB populations with a spatially explicit,
climate-driven simulation tool. Historic weather records were used to produce
maps of the distribution of past climatically suitable habitats for MPB in British
Columbia. Overlays of annual MPB occurrence on these maps were used to
determine if the beetle has expanded its range in recent years due to changing
climate. An examination of the distribution of climatically suitable habitats in 10year increments derived from climate normals (1921-1950 to 1971-2000) clearly
shows an increase in the range of benign habitats. Furthermore, an increase (at
an increasing rate) in the number of infestations since 1970 in formerly
climatically unsuitable habitats indicates that MPB populations have expanded
into these new areas.
The potential for additional range expansion by MPB under continued global
warming was assessed from projections derived from the CGCM1 global
circulation model and a conservative forcing scenario equivalent to a doubling of
CO2 (relative to the 1980s) by approximately 2050. Predicted weather conditions
were combined with the climatic suitability model to examine the distribution of
benign habitats from 1981-2010 to 1941-2070 for all of Canada. The area of
climatically suitable habitats is anticipated to continue to increase within the
historic range of MPB. Moreover, much of the boreal forest will become
climatically available to the beetle in the near future. Since jack pine is a viable
host for MPB and a major component of the boreal forest, continued eastward
expansion by MPB is probable.
Chansler, J.F. 1966. Cold hardiness of two species of Ips beetles. Journal
of Forestry 64: 622-624.
This paper studied how survival in Ips leconti and Ips confusus is influenced by
natural cold hardening, duration of low temperature, and diameter of infested
trees. At low temperatures bark beetle mortality decreased as bolt diameter and
bark thickness increased.
Abstract: Cold hardiness studies of the overwintering adult stage of two, fivespined Ips were made during the winters of 1960-1961 and 1961-1962. Ips
confuses infesting pinion pine in Arizona and New Mexico, can successfully
withstand 5◦ to 10◦ F colder temperatures than Ips lecontei, a pest of ponderosa
pine in central and southern Arizona. Little, if any, additional cold hardening was
exhibited by either beetle between November and March. Both beetles tolerated
colder temperatures the second year. Mortality varied with air temperature,
length of exposure, bolt diameter, and bark thickness. Natural mortality in the
infested forests verified the accuracy of the laboratory experiments.
Chansler, J.F. 1967. Biology and life history of Dendroctonus adjunctus
(Coleoptera: Scolytidae). Annals Entomological Society America
This paper details the distribution, host selection, life cycle of the roundheaded
pine beetle and factors affecting population density such as management,
predators, temperature, and moisture. The overwintering stages are usually
eggs and egg-laying adults with little development in overwintering eggs. 70% of
the study brood was fourth-instar larvae by late May with 65% in this stage two
months later. This slow rate of development indicates the possibility of diapause.
Abstract: Dendroctonus adjunctus Blandford (D. convexifrons Hopkins), the
roundheaded pine beetle, kills groups of pole sized ponderosa pine, Pinus
ponderosa Laws, in New Mexico and Arizona. The range of this forest pest
extends from southern Utah and Colorado southward through pine forest to
Guatemala. Study of a serious outbreak in southern New Mexico showed the
insect to have a 1-year life cycle. The attack period lasts 8-9 weeks, peaking in
mid October. The insect overwinters in the egg and egg-laying adult stages.
Development resumes in late March. The larval stage occurs between April and
July, pupation in August. Certain physical and biotic factors appear to play an
important part in the sudden rise and fall of outbreaks.
Cibrián-Tovar, D., Méndez-Montiel, J.T., Campos-Bolaños, R., Yates III, H.O.,
Flores-Lara, J. 1995. Insectos forestales de México / Forest Insects of
Mexico. Universidad Autónoma Chapingo y Comisión Forestal de América
del Norte, FAO. Publicación/Publication No.6.
This book focuses on phytophagus insects affecting forest and forest products
and is organized as to species, host, distribution, description,life cycle, and
management. D. adjunctus is a major pest in National Parks in central Mexico
and in forests at altitudes above 2800m. Most attacks occur from September to
November with egg laying occuring from August to January the following year.
Clarke, L.E., Edmonds, J.A., Jacoby, H.D., Pitcher, H.M., Reilly, J.M.,
Richels, J.M. 2007. Scenarios of greenhouse gas emissions and
atmospheric concentrations. Sub-report 2.1A of Synthesis and
Assessment Product 2.1 by the U.S. Climate Change Science Program and
the Subcommittee on Global Change Research. Department of Energy,
Office of Biological & Environmental Research, Washington, DC.
This synthesis and assessment uses three models IGSM, MERGE, and MiniCAM
to develop reference scenarios detailing possible outcomes, scenarios that
stabilize radiative forcing, and suggests future directions for users and
policymakers. In the reference scenarios, CO2 emissions from fossil fuel
combustion and industrial processes increase to over 3 times their current levels
by 2100. Concentrations of atmospheric CO2 are expected to increase to 700
ppmv -900 ppmv from the current level of 365 ppmv during the same period.
Abstract: This and a companion report constitute one of twenty-one Synthesis
and Assessment Products called for in the Strategic Plan for the U.S. Climate
Change Science Program. These studies are structured to provide high-level,
integrated research results in important science issues with a particular focus on
questions raised by decision-makers on dimensions of climate change directly
relevant to the U.S. One element of the CCSP’s strategic vision is to provide
decision support tools for differentiating and evaluating response strategies.
Scenario-based analysis is one such tool. The scenarios in this report explore the
implications of alternative stabilization levels of anthropogenic greenhouse gases
(GHGs) in the atmosphere, and they explicitly consider the economic and
technological foundations of such response options. Such scenarios are a
valuable complement to other scientific research contained in the twenty-one
CCSP Synthesis and Assessment Products. The companion to the research
reported here, Global-Change Scenarios: Their development and Use, explores
the broader strategic frame for developing and utilizing scenarios in support of
climate decision making.
Cole, W.E. 1981. Some risks and causes of mortality in mountain pine
beetle populations: a long-term analysis. Researches on Population
Ecology 23:116-144.
This paper discussed factors influencing mortality in mountain pine beetle such
as host diameter, phloem thickness, population density, predators, pitch, and
pathogens. The two main causes of mortality in mountain pine beetle broods are
low winter temperatures and drying of the phloem in early summer. Impact from
these factors decreased as tree diameter and phloem thickness increased.
Abstract: The interpretation of the probabilities presented in this paper is that
none of the competing biological risks, acting in the presence of other risks,
offers much, if any, regulatory influence upon a mountain pine beetle population.
Consequently, if no single risk, or combination of these risks, offers much help,
then the contention that mountain pine beetle populations are food-regulated is
once again strengthened (COLE and AMMAN, 1969). The evidence remains (or
continues) that the mountain pine beetle is food-regulated at optimum
temperature conditions and temperature-regulated at optimum food conditions.
Reducing and/or minimizing tree loss to the mountain pine beetle is thus
dependent upon manipulating the food supply or management of the tree (stand)
growth.
Coley, P.D. 1998. Possible Effects of Climate Change on Plant/Herbivore
Interactions in Moist Tropical Forests. Climatic Change 39(2-3): 455-472.
This paper discusses the effects of elevated CO2, drought, and temperature
individually as well as the overall effects of climate change on plants, herbivores,
and natural enemies. Shortened developmental times in herbivores due to
increased temperature should decrease parasitoid susceptibility. Climate change
may compromise the ability of natural enemies to control herbivore populations
resulting in a change in relative species abundance.
Cook, E.R., Seager, R., Cane, M.A., Stahle, D.W. 2007. North American
drought: Reconstructions, causes and consequences. Earth-Science
Reviews 81: 93-134.
This study used tree ring records to reconstruct drought and mega-drought
events over the past 1000 years and indicates that severe drought has been the
most common natural disaster in North America during this time. Sea surface
temperature (SST) of the tropical Pacific Ocean drive the patterns of drought,
with warmer air temperatures paradoxically leading to cooler, La Nina like SST
and thus drought in North America. The warming climate due to anthropogenic
green house gases could then result in severe megadroughts as seen in the
medieval period.
Abstract: Severe drought is the greatest recurring natural disaster to strike North
America. A remarkable network of centuries-long annual tree-ring chronologies
has now allowed for the reconstruction of past drought over North America
covering the past 1000 or more years in most regions. These reconstructions
reveal the occurrence of past “megadroughts” of unprecedented severity and
duration, ones that have never been experienced by modern societies in North
America. There is strong archaeological evidence for the destabilizing influence
of these past droughts on advanced agricultural societies, examples that should
resonate today given the increasing vulnerability of modern water-based systems
to relatively short-term droughts. Understanding how these megadroughts
develop and persist is a timely scientific problem. Very recently, climate models
have succeeded in simulating all of the major droughts over North America from
the Civil War to the severe 1998–2004 drought in the western U.S. These
numerical experiments indicate the dominating importance of tropical Pacific
Ocean sea surface temperatures (SSTs) in determining how much precipitation
falls over large parts of North America. Of central importance to drought
formation is the development of cool “La Niña-like” SSTs in the eastern tropical
Pacific region. This development appears to be partially linked to changes in
radiative forcing over that region, which affects the Bjerknes feedback
mechanism of the ENSO cycle there. Paradoxically, warmer conditions over the
tropical Pacific region lead to the development of cool La Niña-like SSTs there,
which is drought inducing over North America. Whether or not this process will
lead to a greater prevalence of drought in the future as the world warms due to
accumulating greenhouse gases is unclear at this time.
Coulson, R.N., Wunneburger, W.F. 2000. Impact of insects on humandominated and natural forest landscapes. Pgs. 271-291 In: Coleman, D.C.,
Hendrix P.F. (eds.), Invertebrates as Webmasters of Ecosystems, CAB
International, Wallingford, UK.
This paper discusses the role of insects on primary production, structure, and
ecological succession in forest landscapes. Herbivory can make plants
vulnerable to pathogens and natural disturbances and can limit reproduction and
regeneration. Bark beetles often target high hazard stands that contain mature
trees with high basal area and stagnant growth
Dale, V.H., Joyce, L.A., McNulty, S., Neilson, R.P., Ayres, M.P., Flannigan,
M.D., Hanson, P.J., Irland, L.C., Lugo, A.E., Peterson, C.J., Simberloff, D.,
Swanson, F.J., Stocks, B.J., Wotton, B.M. 2001. Climate change and forest
disturbances. BioScience 51:723–734.
This study examined the impact of several disturbance regimes on forest
structure, composition, and function and the effect of climate change on the
severity, frequency, and magnitude of those disturbances. Temperature
increases due to climate change will modify developmental rates, dispersal, and
distribution for many species. An increase in minimum winter temperatures may
favor northern migration of the southern pine beetle. Disturbances from
herbivores and pathogens are widespread in the forest community including
elimination of nesting trees.
Abstract: Studies of the effects of climate change on forests have focused on
the ability of species to tolerate temperature and moisture changes and to
disperse, but they have ignored the effects of disturbances caused by climate
change (e.g., Ojima et al. 1991). Yet modeling studies indicate the importance of
climate effects on disturbance regimes (He et al. 1999). Local, regional, and
global changes in temperature and precipitation can influence the occurrence,
timing, frequency, duration, extent, and intensity of disturbances (Baker 1995,
Turner et al. 1998). Because trees can survive from decades to centuries and
take years to become established, climate-change impacts are expressed in
forests, in part, through alterations in disturbance regimes (Franklin et al. 1992,
Dale et al. 2000).
Danks, HV. 1987. Insect Dormancy: An Ecological Perspective. Biological
Survey of Canada (Terrestrial Arthropods) Monograph series no. 1. Tyrell
Press LTD. Gloucester, Ontario. 439p.
This book focused on dormancy, adaptive seasonality, and diapause as a driver
of synchrony for mating, resource availability, and avoidance of harsh
environmental conditions. Temperature is the major determining factor in direct
control of development along with photoperiod, food, population density, and
climate. In many insects, higher temperature based developmental thresholds for
late instars and pupae allow early instars to complete their development
synchronizing the population at a specific life-stage.
Davis, M.B. 1981. Quaternary history and the stability of forest
communities. In West, D.C., Shugart, H.H., Botkin, D.B. (eds.). Forest
Succession: Concepts and Application, p 134-153. D.C. New York,
Springer-Verlag. 517 pp.
This study used pollen morphology to determine the migration rates of several
boreal and temperate deciduous forests during the Quaternary Period. Range
expansion of trees averaged 300 m/yr during the Holocene. The speed of climate
change far exceeded the speed at which forests could adjust.
Davis, M.A., Grime, J.P., Thompson, K. 2000. Fluctuating resources in
plant communities: a general theory of invisibility. Journal of Ecology 88:
528-534.
This paper outlines a theory for establishment of invasive species into new
environments based on fluctuating resource availability. Either a decline in the
use of existing resources by resident vegetation or an increase in resource
supply will result in resource availability. These resources are then available
making communities susceptible to invading species.
DiGuistini, S., Ralph, S.G., Lim, Y.W., Holt, R., Jones, S., Bohlmann, J.,
Breuil, C. 2007. Generation and annotation of lodgepole pine and
oleoresin-induced expressed sequences from the blue-stain fungus
Ophiostoma clavigerum, a Mountain Pine Beetle-associated pathogen.
FEMS Microbiology Letters 267 (2): 151–158.
This study is a genomic analysis of Ophiostoma clavigerum, a fungal associate of
mountain pine beetle, which discolors sapwood in lodgepole pine. O.clavigerum
was grown on three different mediums lodgepole pine sawdust, malt extract agar
(MEA), and MEA supplemented with monoterpene and diterpene metabolites
from lodgepole pine.
Dukes, J.S., Mooney, H.A. 1999. Does global change increase the success
of biological invaders? Trends in ecology and evolution 14: 135-139.
This paper discusses the effects of climate change such as increased
temperature and elevated levels of CO2 on invasive plant and animal species.
Increased carbon dioxide levels will decrease transpiration in plants making more
ground water available for invading species. Warmer temperatures may also
result in decreased generation times and increased winter survival of insects. It is
predicted that insect species will expand their range northerly and upward in
elevation.
Dunn, J.P., Lorio, Jr., P.L. 1993. Modified water regimes affect
photosynthesis, xylem water potential, cambial growth, and resistance of
juvenile Pinus taeda L. to Dendroctonus frontalis (Coleoptera: Scolytidae).
Environmental Entomology 22: 948-957.
This study tested the growth differentiation balance concept usng irrigated and
non-irrigated loblolly pine in both early and late summer experiments to
determine the impact of drought on oleoresin production. Trees experiencing
moderate water deficits may show an increase in carbon partitioning to resin
synthesis relative to plant growth increasing plant defenses. Conversely, an
abundant supply of water can reduce plant defenses as available carbon is used
for growth. Southern pine beetles adjust population densities and attack rates to
overwhelm increasing tree resistance.
Abstract: We modified soil water supply to two groups of juvenile loblolly pines,
Pinus taeda L., by sheltering or irrigating root systems in early summer or in late
summer and measured oleoresin flow (primary defense), net photosynthesis,
xylem water potential, and cambial growth throughout the growing season. When
consistent significant differences in oleoresin flow and water potentials were
detected between treatments, we induced attack by the southern pine beetle,
Dendroctonus frontalis Zimmermann. Compared with irrigated trees, sheltered
trees had lower xylem water potentials, reduced cambial growth, reduced
photosynthesis, and reduced resin flow. In terms of response to beetle attack,
sheltered trees had fewer attacks and less total gallery constructed, but those
beetles that did attack sheltered trees were more successful (50-100% more
eggs per attacking pair). However, the success of attacking beetles was
generally very low, even in sheltered trees (only three to eight eggs per attacking
pair). This performance, along with water deficits that strongly affected tree
physiology, growth, and development, indicates that juvenile loblolly pine can
make internal adjustments that limit the success of southern pine beetle attack.
Dyer, E.D.A. 1969. Influence of temperature inversion on development of
spruce beetle, Dendroctonus obsesus (Mannerheim) (Coleoptera:
Scolytidae). Journal of the Entomological Society of British Columbia 66:
41-45.
This study chronicled the development rate and voltinism of two broods of
Dendroctonus obesus at sites with similar day temperatures but different night
temperatures. Night temperatures at one site repeatedly dropped 5 to 7 degrees
below freezing in late August, resulting in an immature brood which then
overwintered on a semivoltine life cycle. The combination of semivoltine and
univoltine populations that occur in warm temperatures can result in outbreak
populations.
Abstract: In the East Kootenay region of British Columbia, spruce logs infested
by Dendroctonus obesus (Mannerheim) were placed beside thermographs at
three sites. Throughout the summer, the mean and minimum air temperatures
were higher on a mountain slope than in two valley bottoms at similar or lower
elevations. Beetle development was faster on the mountain slope, where it
continued until frost occurred in October, at which time 96% of the progeny were
mature. In the lower valley bottom the minimum temperature fell 3.9 and 2.8 ◦ C (7
and 5◦ F) below freezing on successive nights in August and larval development
stopped. In the valley bottoms only 13 and 9% of the broods matured before
winter. Temperature conditions that allow most broods of D. obesus to mature in
one season may result in a critical addition to the normal number of beetles that
mature after 2 years development.
Dyer, E.D.A. 1970. Larval diapause in Dendroctonus obsesus
(Mannerheim)(Coleoptera: Scolytidae). Journal of the Entomological
Society of British Columbia 67: 18-21.
In this study test logs were infested with broods of Dendroctonus obesus, and
then subjected to different temperature regimes to determine what temperature
conditions induced diapause. Cooler temperatures led to diapause, but the
coldest temperature regime also prevented development to maturity when
diapause ended.
Abstract: Dendroctonus obesus (Mannerheim) larvae diapaused in the last
instar during laboratory rearing with warm thermoperiods reduced to 12 hours or
less, mean temperatures of 50◦ -56◦ F. (10◦ - 13.3◦ C) and at least one minimum
subcortical temperature near or below the larval development threshold during
the third and fourth instars. Larvae reared at constant temperature of 70 ◦ F (21.1◦
C) did not diapause. Prediction of beetle populations and forest damage is
dependent on a knowledge of the seasonal meteorological conditions that affect
larval diapause and subsequently the numbers of mature beetles capable of
initiating attacks. Further investigation is required to determine the separate
effects of brood, age temperatures and thermoperiods on diapause.
Dyer, E.D.A., Hall, P.M. 1977. Factors affecting larval diapause in
Dendroctonus obsesus (Mannerheim)(Coleoptera: Scolytidae). The
Canadian Entomologist 109: 1485-1490.
This study chronicled the effect of temperature on brood development and onset
of diapauses in the spruce beetle Dendroctonus rufipennis (Kirby) under various
temperature regimes. Meteorological conditions can cause spruce beetle instarIV larvae to overwinter in larval or prepupae diapauses. Larvae have a 6.1°C
developmental temperature threshold with development rates increasing as
temperature increases. If night temperatures drop below this threshold for more
than 10 day-degrees per day during instar-III, the larvae will likely enter
diapause.
Abstract: The effect of daily day-degrees C in relation to brood age was
investigated to determine its influence on the induction of larval (prepupal)
diapause in Dendroctonus rufipennis (Kirby). Daily day-degrees of less than
about 9◦ above the development threshold (6.1◦ C) induced diapause in most of
the broods while diapause was averted by daily day-degrees C of 10 or more
above the threshold. Induction of diapause occurred no later than third larval
instar; temperature changes during the fourth instar produced no change in
aversion or induction of diapause. Laboratory results reveal that field
temperatures during larval development determine whether most beetles have a
1- or 2-year life cycle.
Fäldt, J., Martin, D., Miller, B., Rawat, S., Bohlmann, J. 2003. Traumatic
resin defense in Norway spruce (Picea abies): Methyl jasmonate-induced
terpene synthase gene expression, and cDNA cloning and functional
characterization of (+)-3-carene synthase. Plant Molecular Biology 51:117–
133.
This study used TPS probes specific to monoterpene and diterpene synthases to
characterize induced resinosis which is similar to the traumatic resin defense
response in Norway spruce. Stem boring insects and microbial pathogens induce
a traumatic resin defense response in several species of spruce that is similar to
the response in Norway spruce saplings to MeJA. This response includes an
increase in transcription for both monoterpene and diterpene synthases.
Fettig, C.J., Allen, K.K., Borys, R.R., Christopherson, J., Dabney, C.P.,
Eager, T.A., Gibson, K.E., Hebertson, E.G., Long, D.F., Munson, A.S., Shea,
P.J., Smith, S.L., Haverty, M.I. 2006. Effectiveness of bifenthrin (Onyx™)
and carbaryl (Sevin® SL) for protecting individual, high-value trees from
bark beetle attack (Coleoptera: Curculionidae: Scolytinae) in the western
United States. Journal of Economic Entomology 99: 1691-1698.
This study assessed the efficacy of bifenthrin and carbaryl as tools to protect
high value trees often located in residential, recreational, or administrative areas
from bark beetle attack. Six of seven study sites (California, South Dakota,
Arizona, Montana, Colorado, and Nevada) provided sufficient data to determine
that carbaryl (Sevin® SL) was efficacious for two field seasons in protecting trees
from bark beetle attack.
Abstract: High-value trees, such as those located in residential, recreational, or
administrative sites, are particularly susceptible to bark beetle (Coleoptera:
Curculionidae: Scolytinae) attack as a result of increased amounts of stress
associated with drought, soil compaction, mechanical injury, or vandalism. Tree
losses in these unique environments generally have a substantial impact. The
value of these individual trees, cost of removal, and loss of esthetics may justify
protection until the main thrust of a bark beetle infestation subsides. This
situation emphasizes the need for ensuring that effective insecticides are
available for individual tree protection. In this study, we assess the efficacy of
bifenthrin (Onyx) and carbaryl (Sevin SL) for protecting: ponderosa pine, Pinus
ponderosa Dougl. ex Laws., from western pine beetle, Dendroctonus brevicomis
LeConte, in California; mountain pine beetle, Dendroctonus ponderosae Hopkins
in South Dakota; and Ips spp. in Arizona; lodgepole pine, Pinus contorta Dougl.
ex Loud., from D. ponderosae in Montana; pinyon, Pinus edulis Engelm. in
Colorado and Pinus monophylla Torr. & Frem. in Nevada from pinyon ips, Ips
confusus (LeConte); and Engelmann spruce, Picea engelmannii Parry ex.
Engelm. from spruce beetle, Dendroctonus rufipennis (Kirby) in Utah. Few trees
were attacked by Ips spp. in Arizona and that study was discontinued. Sevin SL
(2.0%) was effective for protecting P. ponderosa, P. contorta, and P. monophylla
for two field seasons. Estimates of efficacy could not be made during the second
field season in P. edulis and P. engelmannii due to insufficient mortality in
untreated, baited control trees. Two field seasons of efficacy was demonstrated
in P. ponderosa/D. brevicomis and P. monophylla for 0.06% Onyx. We conclude
that Onyx is an effective individual tree protection tool, but repeated annual
applications may be required in some systems if multiyear control is desired.
Fettig, C.J., Klepzig, K.D., Billings, R.F., Munson, A.S., Nebeker, T.E.,
Negrón, J.F., Nowak, J.T. 2007. The effectiveness of vegetation
management practices for prevention and control of bark beetle
infestations in coniferous forests of the western and southern United
States. Forest Ecology and Management 238: 24-53.
This study discusses bark beetle risk and hazard rating models, effects of
vegetation management practices such as thinning and fire treatments on bark
beetle activity in conifer forests. Disturbances caused by management practices
and natural processes have resulted in changes in forest structure and
composition leading to increased competition for water, nutrients, and growing
space. Increased stand density, tree diameter, and stand age result in decreased
vigor. Depending on the host and insect species, current research supports low
thinning, crown thinning, or selection thinning as effective measures for reducing
bark beetle caused tree mortality.
Abstract: Insects are major components of forest ecosystems, representing
most of the biological diversity and affecting virtually all processes and uses. In
the USA, bark beetles (Coleoptera: Curculionidae, Scolytinae) heavily influence
the structure and function of these ecosystems by regulating certain aspects of
primary production, nutrient cycling, ecological succession and the size,
distribution and abundance of forest trees. The purpose of this report is to review
tree and stand factors associated with bark beetle infestations and analyze the
effectiveness of vegetation management practices for mitigating the negative
impacts of bark beetles on forest ecosystems. We describe the current state of
our knowledge and identify gaps for making informed decisions on proposed
silvicultural treatments. This review draws from examination of 498 scientific
publications (many of which are cited herein) on this and related topics.
Flannigan, M.D., Stock, B.J., Wotton, B.M. 2000. Climate change and forest
fires. The Science of The Total Environment 262(3): 221-229.
This paper assesses the current impact of fire regimes in U.S. forests and
discusses the role of climate change on future fire and other disturbance
regimes. Two General Circulation Models predict a longer fire season and
increases in fire risk of 10-50% across much of the United States, in particular
Alaska and the southeastern U.S., and to a lesser extent the western states in
general. This increase in fire risk has the greatest potential of all climate-driven
change to rapidly change forest type, species distribution, migration and
extinction.
Fowler, H.J., S. Blenkinsop and C. Tebaldi. 2007. Linking climate change
modeling to impacts studies: recent advances in downscaling techniques
for hydrological modeling. International Journal of Climatology 27:15471578.
This review of current downscaling literature discusses dynamical and statistical
downscaling and the need to improve predictive hydrologic modeling. One
approach to assess uncertainties in future climate projections is to merge
downscaling techniques with probabilistic modeling, pattern scaling, and multiple
variable downscaling.
Franceschi, V.R., Krokene, P., Christiansen, E., Krekling, T. 2005.
Anatomical and chemical defenses of conifer bark against bark beetles and
other pests. New Phytologists 167: 353-376.
This paper studied constitutive defenses in conifers such as the periderm, cortex,
and secondary phloem as well as inducible chemical and anatomical defenses
conifers have evolved to repel bark beetle attack. Constitutive defenses in
conifers are determined by genetics while inducible defenses vary by the nature
and severity of the attack. Many organisms have developed strategies to
overcome both anatomical and chemical defenses of conifers. Aggressive bark
beetles all have some tolerance to host terpenes and have evolved to synthesize
aggregation pheromones from host monoterpenes.
Frich, P., Alexander, L.V., Della-Marta, P., Gleason, B., Haylock, M., Tank
Klein, A.M.G.., Peterson, T. 2002. Observed coherent changes in climatic
extremes during the second half of the twentieth century. Climate
Research 19: 193-212.
This study followed the climatic extremes for the second half of the 20th century
and created a global dataset derived from direct day to day observations and a
set of 10 indicators. Over this period the world on average has become both
wetter and warmer with minimum temperatures increasing more than maximum
temperatures. Extreme weather events have increased over this time frame in
keeping with predicted changes in climate.
Gandhi, K.J.K., Gilmore, D.W., Katovich, S.A., Mattson, W.J., Spence, J.R.,
Seybold, S.J. 2007. Physical effects of weather events on the abundance
and diversity of insects in North American forests. Environmental Reviews
15:113-152.
This paper discusses the impact of weather related events such as wind and ice
storms on insect population dynamics. Following wind storms geographic
location, elevation, forest type, and the severity and extent of the windthrow
determine the genera and species of insects that are dominant. Outbreaks are
often of short duration lasting only a few years until a buildup of predators and/or
lack of suitable host material occurs. In Europe there have been outbreaks in
which less aggressive beetles have multiplied to sufficient numbers to begin kill
living trees.
Abstract: We summarize the effects of major weather events such as ice storms,
wind storms, and flooding on the abundance and diversity of terrestrial forest
insects and their allies. This synthesis indicates that weather events influence
both spatial and temporal patterns of forests and insect communities in North
American landscapes. The Atlantic and Pacific oceanic sides of the continent are
relatively more susceptible to ice and wind storms, respectively. There have been
more studies and reports on the responses of forest insects to wind storms, and
on economically important subcortical insects than on gall-forming, foliagefeeding, fungal-feeding, litter-dwelling, pollinating, parasitizing, predaceous, rootfeeding, and sap-feeding insects. Weather events positively affect populations of
subcortical insect species, and impact their colonization patterns and dynamics.
Species belonging to genera such as Dendroctonus (Scolytidae) and
Monochamus (Cerambycidae) may sometimes cause economic damage by
colonizing residual live tree, and dead trees, rendering the wood unsalvageable.
Subsequent outbreaks of spruce beetle, Dendroctonus rufipennis (Kirby) and
Douglas-fir beetle, Dendroctonus pseudotsugae Hopkins, have been frequently
documented in western North American forests following wind events. Wind
disturbances have also been observed to accelerate the life-cycles of D.
rufipennis and Semanotus litigiosus (Casey) (Cerambycidae), and in rare
instances, have caused Monochamus spp. to become primary colonizers.
Populations of other important subcortical species have not always increased
dramatically following weather events. Foliage- and pollen-feeding insects may
experience mortality directly from a weather event or indirectly through habitat
alteration. In some cases, forest insects may use storms to migrate to new
habitats. Populations of open-habitat and forest specialist litter-dwelling species
have increased and decreased, respectively, subsequent to weather events.
Forest specialist species generally rebound within a short period of time,
suggesting that they are adapted to these periodic weather events. Little is
known about the combined effects of post-weather-disturbance management
practices such as salvage-logging and prescribed-burning on insects in North
American forests.
Gaylord, M.L., Kolb, P.E. Wallin, K.F., Wagner, M. 2006. Seasonality and
lure preference of bark beetles (Curculionidae: Scolytinae) and associates
in a Northern Arizona ponderosa pine forest. Environmental Entomology
35: 37-47.
This study used pheromone-mediated trap catch data to describe the flight
periodicity and lure preferences for bark beetles and their predators. Results from
the study site suggest that bark beetles and their associated predators begin
emergence in April with most flight occurring between May and the end of
October.
Gehrken, U. 1984. Winter survival of an adult bark beetle Ips acuminatus
Gyll. Journal of Insect Physiology 30(5): 421-429.
This paper studied the effects of different temperature regimes on the
accumulation of cyroprotective solutes determining the supercooling point of I.
acuminatus and the loss of cold hardiness after exposure to warmer
temperatures. Although some arthropods are able to supercool in the absence of
accumulated solutes, most show a linear relationship between decreasing
supercooling points and higher cryoprotective solute concentrations. In I.
acuminatus the supercooling point was depressed to a greater extent than was
the haemolymph. Higher temperatures resulted in a reduction of cryoprotective
solutes. Once cryoprotection was lost the process is irreversible.
Gibson K.E. 2006. Mountain pine beetle conditions in whitebark pine
stands of the Greater Yellowstone Ecosystem. Forest Health Protection
Report 6-03.
This study cites lack of precipitation, increased temperature, and stands that
have not experienced disturbances for decades for an increased susceptability to
mountain pine beetle outbreaks. Mountain pine beetle outbreaks can kill millions
of mature trees until depleting the availability of suitable hosts or environmental
conditions change.
Abstract: Mountain pine beetle, Dendroctonus ponderosae Hopkins, (MPB)
populations are currently at outbreak status in many parts of the intermountain
West. More than one million acres of host stands are infested to some extent in
the Northern Region alone. Most infested acres are in lodgepole pine stands;
however, almost 143,000 of them are in whitebark pine (WBP). In the Northern
Region, unusually high amounts of MPB-infested WBP stands are found in
northern Idaho and west-central Montana in addition to forests in southwestern
Montana, and Yellowstone National Park (NP)—the latter a part of the Greater
Yellowstone Ecosystem (GYE). In 2005, we recorded the highest level of MPBcaused WPB mortality in any one year for which we have data. Unpublished
office reports indicate a similar series of outbreaks existed in the 1930s—another
period of unusually warm temperatures—in Southeastern Idaho, Southwestern
Montana and Yellowstone NP; but we have no records documenting the extent of
those outbreaks. By most accounts, those outbreaks were probably at least as
extensive as current ones. So, while present outbreaks are devastating and
unusual; they are likely not unprecedented.
Gilbert E., Powell J.A., Logan J.A., Bentz B.J. 2004. Comparison of three
models predicting developmental milestones given environmental and
individual variation. Bulletin of mathematical biology 66(6): 1821-1850.
This study compared the Extended von Foerster model, distributed delay model,
and the Sharpe and Michele model for accuracy in the prediction of development
rates for mountain pine beetle Dendroctonus ponderosae (Hopkins). In
poikilothermic organisms, the rate of metabolism is determined by the
temperature of their habitat. Synchronization of life-stages is strongly enhanced
by temperature induced periods of quiescence when development stops.
Abstract: In all organisms, phenotypic variability is an evolutionary stipulation.
Because the development of poikilothermic organisms depends directly on the
temperature of their habitat, environmental variability is also an integral factor in
models of their phenology. In this paper we present two existing phenology
models, the distributed delay model and the Sharpe and DeMichele model, and
develop an alternate approach, called the Extended von Foerster model, based
on the age-structured McKendrick-von Foerster partial differential model. We
compare the models theoretically by examining the biological assumptions made
in the basic derivation of each approach. In particular, we focus on each model’s
ability to incorporate variability among individuals as well as variability in the
environment. When compared against constant temperature mountain pine
beetle (Dendroctonus ponderosae Hopkins) laboratory developmental data, the
Extended von Foerster model exhibits the highest correlation between theory and
observation.
Gitay, H., Brown, S., Easterling, W., Jallow, B. 2001. Ecosystems and their
goods and services. In Climate Change 2001: Impacts, Adaptation, and
Vulnerability. J. McCarthy, O. Canziani, N. Leary, D. Dokken, and K. White
(eds.). Cambridge University Press, Cambridge, England.
This chapter covers current experimental evidence regarding climate change and
future expectations of the impact of climate change on agriculture, wildlife,
forests, woodlands, arctic and alpine ecosystems as well as wetlands, lakes, and
streams. Boreal forests will likely experience the earliest and largest impacts of
global warming and have already shown a change in seasonal thaw patterns and
a lengthened growing season. Many boreal forests will have an increase in NPP
as a result of longer growing seasons and increasing heat sums.
Gomi, T., Takeda, M. 1996. Changes in Life-History Traits in the Fall
Webworm within Half a Century of Introduction to Japan. Functional
Ecology, Vol.10, No. 3, 384-389.
This study determined that changes in development rate and/or critical
photoperiod can cause a shift from a bivotine to a trivoltine life cycle. This change
occurred in a population of Fall Webworm within 40 years after successful
colonization of Japan.
Grulke, N.E., Minnich, R.A., Paine, T.D., Seybold, S.J., Chavez, D., Riggan,
P.J., Dunn, A. 2008. Air pollution increases forest susceptibility to
wildfires: A case study in the San Bernardino Mountains in southern
California, Pgs. xxx-xxx, In: A. Bytnerowicz and M. Arbaugh (eds.), Air
Pollution and Fire, Developments on Environmental Science, Elsevier
Science, San Diego in press.
This chapter links the use of fossil fuels and the increase in greenhouse gasses
such as nitrogen oxides and ozone and their effects on forest health and
susceptibility to bark beetle outbreaks and fire. Elevated nitrogen levels increase
aboveground forest biomass, increasing forest density and ground litter while
slowing decomposition rates. Ozone reduces photosynthesis and increases
susceptibility to drought, which in turn increases risk of beetle attack. Trees
killed from drought or beetle attack in turn increase the severity of fire hazard.
Abstract: Many factors increase susceptibility of forests to wildfire. Among
them are increases in human population, changes in land use, fire
suppression, and frequent droughts. These factors have been exacerbating
forest susceptibility to wildfires over the last century in southern California.
Here we report on the significant role that air pollution has on increasing forest
susceptibility to wildfires, as unfolded in the San Bernardino Mountains from
1999 to 2003. Air pollution, specifically ozone (O3), and wet and dry deposition
of nitrogenous compounds from fossil fuel combustion, has significantly
increased since industrialization of the region after WWII. Ozone and elevated
nitrogen deposition cause specific changes in forest tree carbon, nitrogen, and
water balance that enhance individual tree susceptibility to drought and bark
beetle attack, and these changes contribute to whole ecosystem susceptibility
to wildfire. For example, elevated O3 and N deposition increase leaf turnover
rates and leaf and branch litter, and decrease decomposability of litter.
Uncharacteristically, deep litter layers develop in mixed conifer forests affected
by air pollutants. Elevated O3 and N deposition decrease the proportion of
whole tree biomass in foliage and roots, the latter effect increasing tree
susceptibility to drought and beetle attack. Because both foliar and root mass
is compromised, carbohydrates are stored in the bole over winter. Elevated O 3
increases drought stress by significantly reducing plant control of water loss.
The resulting increase in canopy transpiration, combined with [O3 + N
deposition]-induced decreases in root mass significantly increase tree
susceptibility to drought stress, and when additionally combined with increased
bole carbohydrates, perhaps all contribute to success of bark beetle attack.
Phenomenological and experimental evidence is presented to support the role
of these factors contributing to the susceptibility of forests to wildfire in
southern California.
Handa, I.T., Körner, C., Hättenschwiler, S. 2006. Conifer stem growth at the
altitudinal treeline in response to four years of CO2 enrichment. Global
Change Biology 12: 2417-2430.
This study used free air CO2 enrichment (FACE) experiments to determine the
effects of elevated CO2 on two treeline ecotone conifer species under natural
conditions. CO2 enrichment resulted in enlarged tracheids and decreased cell
wall thickness for L. sibirica impacting its ability to withstand environmental
forces. Changes in tracheid diameter may also impact water conductivity making
conifers in colder climates vulnerable to freezing induced embolisms.
Hansen, A.J., R.P. Nielson, V.H. Dale, C.H. Flather, L.R. Iverson, D.J. Currie,
S. Shafer, R. cook, P.J. Bartlein. 2001. Global change in forests: Responses
of species, communities and biomes. Bioscience 51: 765-779.
This study synthesizes the current knowledge regarding land use and climate
change and projects the impacts on species diversity, communities, and biomes.
Global changes in land use and climate effect abundance and distribution of
species. The disturbance of even a single species within a system can cause a
chain of reaction within that system, which in turn can feed back to influence
climate and land use, and thus affect human well-being.
Abstract: Global change is often perceived as human-induced modifications in
climate. Indeed, human activities have undeniably altered the atmosphere, and
probably the climate as well (Watson et al. 1998). At the same time, most of the
world’s forests have also been extensively modified by human use of the land
(Houghton 1994). Thus, climate and land use are two prongs of human-induced
global change. The effect of these forces on forests is mediated by the
organisms within forests. Consideration of climate, land use, and biological
diversity is key to understanding forest response to global change.
Biological diversity refers to the variety of life at organizational levels from
genotypes through biomes (Franklin 1993). The responses of ecological systems
to global change reflect the organisms that are within them. While ecologists
have sometimes not seen the forest for the trees, so to speak, it is also true that
forests cannot be understood without knowledge of the trees and other
component species. It is the responses of individual organisms that begin the
cascade of ecological processes that are manifest as changes in system
properties, some of which feed back to influence climate and land use (Figure 1).
Beyond its role in ecosystems, biodiversity is invaluable to humans for foods,
medicines, genetic information, recreation, and spiritual renewal (Pimentel et al.
1997). Thus, global changes that affect the distribution and abundance of
organisms will affect future human well-being and land use, as well as, possibly,
the climate. This article serves as a primer on forest biodiversity as a key
component of global change. We first synthesize current knowledge of
interactions among climate, land use, and biodiversity. We then summarize the
results of new analyses on the potential effects of human-induced climate
change on forest biodiversity. Our models project how possible future climates
may modify the distributions of environments required by various species,
communities, and biomes. Current knowledge, models, and funding did not allow
these analyses to examine the population processes (e.g., dispersal,
regeneration) that would mediate the responses of organisms to environmental
change. It was also not possible to model the important effects of land use,
natural disturbance, and other factors on the response of biodiversity to climate
change. Despite these limitations, the analyses discussed herein are among the
most comprehensive projections of climate change effects on forest biodiversity
yet conducted. We conclude with discussions of limitations, research needs, and
strategies for coping with potential future global change.
Hansen, E.M., Bentz, B.J. 2003. Comparison of reproductive capacity
among univoltine, semivoltine, and re-emerged parent spruce beetles
(Coleoptera: Scolytidae). Canadian Entomologist. 697-712,
This study examined the differences in lipid content, gallery construction, egg
production, brood development rates, and brood survival in semi-voltine,
univoltine, and re-emerged parent spruce beetles. The growth rate for univoltine
populations may increase further due to decreased exposure to weather and
predation. During extended periods of warmer summers, univoltine and
semivoltine populations can combine to increase the probability of a spruce
beetle outbreak.
Abstract: New spruce beetle, Dendroctonus rufipennis (Kirby), adults of
univoltine and semivoltine life cycles, as well as re-emerged parent beetles, were
laboratory-tested for differences in reproductive capacity and brood
characteristics. Parameters measured from the three groups include dry weight,
lipid content, and egg production. Brood characteristics measured include egg
length, development rates, and survival densities. Although there were some
differences in dry weight and lipid content, females from the univoltine,
semivoltine, and re-emerged parent groups did not greatly differ in egg
production. Egg length was slightly smaller for eggs from univoltine parents, but
other measured brood characteristics did not differ among the three parent
groups, including the density of the surviving brood. In a field study, re-emerged
parents were determined to be flight capable. These findings imply that
populations with univoltine broods will have higher growth rates than semivoltine
populations. Consequently, the presence of univoltine broods, which is weather
dependent, increases the risk of a beetle outbreak or can accelerate the rate of
spruce mortality in an established outbreak. These results also indicate that reemerged parent beetles can contribute substantially to brood production.
Suppression strategies can be more effective if managers consider the ecological
consequences of brood production from the three parent groups.
Hansen, E.M., Bentz, B.J., Turner, D.L. 2001a. Physiological basis for
flexible voltinism in the spruce beetle (Coleoptera: Scolytidae). The
Canadian Entomologist 133 (6): 805-817.
In this study adult spruce beetle pairs (Dendroctonus rufipennis Kirby) were
introduced into bolts and phloem sandwiches to determine the effects of constant
temperature as well as thermoperiod and photoperiod on brood success and
larval development. Spruce beetles are suspected to have a diapause, which
results from a hypothesized 150 or more days at 5.5 and 7°C and occurring in
late instar IV or early prepupal life stages. Temperature is also strongly related
to voltinism in bark beetles, but diapuase should not be considered the causal
agent in determining voltinism in the spruce beetle. Instead, diapauses may
occur in late fall to prevent over-wintering in cold-susceptible life stages.
Abstract: The spruce beetle, Dendroctonus rufipennis (Kirby), has described life
cycles of 1-3 years. Although temperature has been shown to be strongly
associated with flexible voltinism in the spruce beetle, the physiological basis for
this phenomenon is not clear. Two competing hypotheses were tested under
laboratory conditions. First, we tested the hypothesis that larval diapause,
induced by cool temperatures during of before instar III, initiates prolonged life
cycles while larvae not diapausing complete development to adults before the
first winter. We compared development times at constant temperature (12 ◦C) and
filed-simulated thermoperiod treatments against development times in a
reference (21◦C) treatment for which there is no indication of diapause induction.
The constant temperature treatment not significantly longer than the reference
treatment, but only by a few days. These results provide little support for the
hypothesis of larval diapause induction during or before instar III. Second, we
investigated the hypothesis of life-cycle regulation through life stage specific
developmental temperature thresholds, particularly, a relatively high threshold for
pupation that might prevent development beyond the prepupal life stage under
cool conditions. We found little evidence of distinct differences in lowtemperature thresholds between life stages. Instar-IV larvae held at <15◦C,
however, did not pupate for 125-300 days, a developmental arrest that suggests
diapause. Based on all present and previous investigations, the inductionsensitive phase appears to be late in the instar-IV or early in the prepupal stages.
For semivoltine spruce beetles, this life stage occurs late in the growing season,
after most temperature-dependant development has been completed. It is our
conclusion that spruce beetle voltinism is primarily under direct temperature
control and that prepupal diapause is the default overwintering strategy for
individuals not completing development to maturity by fall.
Hansen, E.M., Bentz, B.J., Turner, D.L. 2001b. Temperature-based model
for predicting univoltine brood proportions in spruce beetle (Coleoptera:
Scolytidae). The Canadian Entomologist 133:827–841.
This study recorded temperatures at eight sampling areas determined within one
week of spruce beetle infestation and used that data to produce a temperature
based model for predicting spruce beetle voltinism. The timing of thermal input,
rather than a single temperature threshold, is crucial in determining spruce beetle
voltinism. The aspect and location of the tree bole further influences these
dynamics (south facing tree boles receive more solar radiation). The model uses
cumulative hours above 17°C that elapse from 40 to 90 days after peak flight as
well as six aspects by height specific inputs to determine percentage of univoltine
or multivoltine broods in a stand.
Abstract: The spruce beetle, Dendroctonus rufipennis (Kirby), has possible life
cycles of 1 or 2 years. Empirical and experimental evidence suggest that
temperature is the primary regulator of these life-history pathways. These
different life cycles potentially result in substantial differences in population
dynamics and subsequent spruce mortality. A multiyear field study was
conducted in Utah, Colorado, and Alaska, to monitor spruce beetle development
under a variety of field conditions with concurrent air temperature measurements.
This information was used to model the tree- or stand-level proportion of
univoltine beetles as a function of air temperature. Temperatures were
summarized as averages, cumulative time, and accumulated heat units above
specified thresholds over various seasonal intervals. Sampled proportions of
univoltine insects were regressed against the summarized temperature values in
logistic models. The best predictive variable, as evaluated by Akaike’s
Information Criterion, was found to be cumulative hours above a threshold of
17◦C elapsed from 40 to 90 days following peak adult funnel-trap captures.
Because the model can be used to forecast trends in spruce beetle populations
and associated spruce mortality, it is a tool for forest planning.
Hanson, P.J., Weltzin, J.F. 2000. Drought disturbance from climate
change: Response of United States forests. The Science of the Total
Environment 262:205–220.
This paper discusses current drought conditions and future drought projections
as a result of climate change and the impact of drought on individual plants and
forest communities. Some general circulation models predict increased drought
occurrence in the western United States. Mortality of seedlings and saplings is
predicted as well as increased susceptibility of mature trees to insect attack and
disease. The anthropogenic driven increase of CO2 in the atmosphere may
mediate the effects of drought, as plant water use will be reduced.
Herms, D.A., Mattson, W.J. 1992. The dilemma of plants: To grow or
defend. The Quarterly Review of Biology 67: 283-335.
This paper discusses the strong inverse relationship between allocation to growth
and allocations to maintenance, storage, reproduction and defense. Phenolic
synthesis as well as alkaloid synthesis, with its amino acid precursors, competes
with growth for common substrates.
Herweijer, C., Seager, R., Cook, E.R., Emile-Geay, J. 2007. North American
droughts of the last millennium from a gridded network of tree-ring data.
Journal of Climate 20: 1353-1376.
This paper used tree ring and surface sea temperature data to study ENSO
induced hydroclimatic variability and the severity and persistence of droughts
over the past 1000 years. Modern day droughts are equal in severity and spatial
distribution to the mega-droughts that occurred between the eleventh and
fourteenth centuries. Modern droughts last only a few years whereas the
Medieval mega-droughts were persistent and often lasted for decades.
Hicke, J.A., Jenkins, J.C. 2008. Mapping lodgepole pine stand structure
susceptibility to mountain pine beetle attack across the western United
States. Forest Ecology and Management 255(5-6): 1536-1547.
This study used plot level stand age, stem density and basal area data from the
Resources Plannign Act inventory to develop county level stand structure and
pine structure susceptibility indices. Stand structure, beetle populations and
climatic suitability all influence mountain pine beetle outbreak potential.
Abstract: Mountain pine beetle (MPB) outbreaks are important disturbances of
forests in the western United States. Stand conditions influence the success of
MPB attack through food availability, shelter, and effects on tree vigor and thus
the ability of a tree to withstand MPB infestation. We estimated the contribution of
stand structure to susceptibility to MPB-caused mortality in lodgepole pine forests
by applying a model that incorporates stand age, stem density, and basal area by
species. We utilized tree-level measurements across the western United States
from the USDA Forest Service Resources Planning Act inventory database that
permitted plot-level and county-level analysis. In the western United States, we
found that stands were typically in age classes (60–120 years) and stem
densities (>400 stem ha_1) that are highly susceptible. A third structural factor,
the percentage of susceptible pine basal area within a stand (compared to all
trees within that stand), typically reduced stand susceptibility across the region.
However, when we considered the susceptibility of only the pine component
instead of the entire stand, we found substantially increased susceptibility index
values. Regional susceptibility was high (pine component susceptibility index
>50, which has been related in past studies to 34% loss of stand basal area) for
2.8 Mha, or 46%, of lodgepole pine forest. Maps revealed variability among
regions, with the highest susceptibility in the southern Rocky Mountains and the
lowest in the coastal states. Our analysis provides useful information to land
managers concerned with future forest ecosystem dynamics and forest
susceptibility to MPB outbreak.
Hicke, J.A., Logan, J.A., Powell, J., Ojima, D.S. 2006. Changing
temperatures influence suitability for modeled mountain pine beetle
outbreaks in the western United States. Journal of Geophysical Research
11:GO2019, doi:10.1029/2005JG000101.
This study modeled current spatial patterns of adaptive seasonality and analyzed
the furure impacts of climate on adaptive seasonality in the mountain pine beetle.
A reduction in adaptive seasonality resulting from warming temperatures may
impact insect disturbances at lower elevations and shift some lodgepole pine
stands from intermediate succession stage to climax stage. Mountain pine beetle
populations at higher elevations in the Northern and Middle Rockies have shown
an increase in adaptive seasonality resulting in outbreaks in novel environments.
Abstract: Insect outbreaks are significant disturbances in forests of the western
United States, with infestation comparable in area to fire. Outbreaks of mountain
pine beetle (Dendroctonus ponderosae Hopkins) require life cycles of one year
with synchronous emergence of adults from host trees at an appropriate time of
year (termed ‘‘adaptive seasonality’’) to overwhelm tree defenses. The annual
course of temperature plays a major role in governing life stage development and
imposing synchrony on mountain pine beetle populations. Here we apply a
process-based model of adaptive seasonality across the western United States
using gridded daily temperatures from the Vegetation/Ecosystem Modeling and
Analysis Project (VEMAP) over the period 1895–2100. Historical locations of
modeled adaptive seasonality overlay much of the distribution of lodgepole pine
(Pinus contorta Douglas), a favored host, indicating that suitable temperatures for
outbreak occurred in areas of host availability. A range of suitable temperatures,
both in the mean and over an annual cycle, resulted in adaptive seasonality.
Adaptive seasonality typically occurred when mean annual temperatures were
3◦C –6◦C, but also included locations where mean temperatures were as low as
1◦C or as high as 11◦C, primarily as a result of variability in winter temperatures.
For most locations, years of adaptive seasonality were uncommon during 1895–
1993. We analyzed historical temperatures and adaptive seasonality in more
detail in three northern forest ecoprovinces. In the Northern and Middle Rockies,
areas of adaptive seasonality decreased at lower elevations and increased at
higher elevations during warmer periods, resulting in a movement upward in
elevation of adaptive seasonality. In contrast, the Cascade Mountains exhibited
overall declines in adaptive seasonality with higher temperatures regardless of
elevation. Projections of future warming (5◦C in the western United States)
resulted in substantial reductions in the overall area of adaptive seasonality. At
the highest elevations, predicted warmer conditions will result in increases in the
area of adaptive seasonality. Our findings suggest that future climate change
may alter forest ecosystems indirectly through alteration of these important
disturbances.
Hill, J. K., C. D. Thomas and B. Huntley. 1999. Climate and habitat
availability determine 20th century changes in a butterfly’s range margin.
Proceedings of the Royal Society Series B Biology 226:1197-206.
This study used historical climate data and present distribution of Pararge
aegeria to test the proposed model and predict future distribution as a result of
climate change. P. aegeria has re-expanded its distribution in the UK during the
20th century as areas in the northern range margin have become more
climatically suitable. Historical data show that climate and distribution of habitat
may be important factors in determining species distribution.
Hoerling, M., Eischeid, J., Quan, X., Xu, T. 2007. Explaining the record US
warmth of 2006. Geophysical Research Letters 34: L17704,
doi:10.1029/2007GL030643.
This study used modeling to test the possibility of greenhouse gas forcing or El
Niño as the cause of the record warmth of 2006 in the United States. Only 1% of
the El Niño model simulations produced temperatures as warm as were
observed in 2006 in the United States as compared to 15% of the model
simulations under greenhouse gas forcing. The greenhouse gas signal accounts
for over half of the observed increase in warmth for 2006.
Hoffmann, A. A., A. Anderson, and R. Hallas. 2002. Opposing clines for high
and low temperature resistance in Drosophila melanogaster. Ecology
Letters 5:614-618.
This study assessed genetic variation along a latitudinal cline relating to thermal
traits occurring within the Australian insect species Drosophila melanogaster.
Specimens sampled from higher latitudes were relatively more resistant to cold
shock and recovered faster from chill coma than their low-latitude counterparts.
Low latitude samples were also found to be more heat resistant than high latitude
samples.
Holsten, E.H., RW Their, R.W. Munson, A.S., Gibson, K.E. 1999. The spruce
beetle. Forest Insect Disease Leaflet 127 - US Department of Agriculture,
Forest Service, Washington, DC.
This leaflet describes the spruce beetle life cycle, preferred stand conditions, and
silvicultural and chemical strategies for managing spruce forests. Stands that are
primarily large diameter old growth spruce, have slow growth rates and high
density are particularly susceptible to spruce beetle attack. There have been as
many as 30 million trees killed per year in 2.3 million acres of Alaskan spruce
forests over the past 7 years.
Abstract: The spruce beetle, Dendroctonus rufipennis (Kirby), is the most
significant natural mortality agent of mature spruce. Outbreaks of this beetle have
caused extensive spruce mortality from Alaska to Arizona and have occurred in
every forest with substantial spruce stands. Spruce beetle damage results in the
loss of 333 to 500 million board feet of spruce saw timber annually. More than
2.3 million acres of spruce forests have been infested in Alaska in the last 7
years with an estimated 30 million trees killed per year at the peak of the
outbreak. In the 1990’s, spruce beetle outbreaks in Utah infested more than
122,000 acres and killed more than 3,000,000 spruce trees. In the past 25 years,
outbreaks have resulted in estimated losses of more than 25 million board feet in
Montana, 31 million in Idaho, Over 100 million in Arizona, 2 billion in Alaska, and
3 billion in British Columbia.
Holsten, E. H., Webb, W., Shea, P. J, Werner, R. A. 2002. Release rates of
methylcyclohexenone and verbenone from bubble cap and bead releasers
under field conditions suitable for the management of bark beetles in
California, Oregon, and Alaska. RP-PNW-544. U.S. Department of
Agriculture, Forest Service, Portland, OR.
This paper studied the release rates of MCH and verbenone at various sites and
temperatures from bubble cap and bead releasers as tools to utilize in the
management of bark beetle outbreaks. Saturation vapor pressure (which
increased exponentially with temperature) and membrane conductance
determine release rates of verbenone bubble caps. Higher temperatures initially
caused a rapid release rate of MCH resulting in lower release rates later in the
season.
Abstract: Devices releasing antiaggregation pheromones, such as MCH (3methyl-2-cyclohexen-1-one) and verbenone (4-methylene-6,6dimethylbicyclo(3.1.1)hept-2-ene), are used experimentally to manipulate
destructive populations of bark beetles. Two slow release devices, bubble caps
attached to boles of trees and granular beads placed on the ground, were tested
in forests of California, Oregon, and Alaska to determine their release rates. The
hypothesis was that ambient air and soil temperatures were major determinants
in the release rates of the releaser devices. Release rates of both bubble caps
and beads differed greatly. The fastest rate was for bubble caps at a warm,
California pine (Pinus spp.) site where it was 15 times faster than the rate at a
cool Sitka spruce (Picea sitchensis Bong. Carr.) site in Alaska. Beads released
MCH quickly and were rendered ineffective in less than 2 weeks. Little or no
release occurred thereafter, regardless of the amount of pheromone remaining in
the bead, or litter layer temperature. Release rates determined under field
conditions are useful for the field entomologist and are vital to the development of
models for semiochemical dispersion.
Huber, D.P.W., Phillipe, R.N., Madilao, L.L., Sturrock, R.N., Bohlmann, J.
2004. Changes in anatomy and terpene chemistry in roots of Douglas-fir
seedlings following treatment with methyl jasmonate. Tree Physiology
25:1075–1083.
This study used methyl jasmonate (MeJA) to induce anatomical, chemical and
biochemical reactions similar to those observed by plants exposed to mechanical
or insect damage. Terpene synthase activity increased after stem and foliage
application of MeJA with many families showing increased concentrations of
monoterpeniods, diterpeniods, and sesquiterpeniods in the wood.
Huey, R.B., Gilchrist, G.W., Carlson, M.L., Berrigan, D., Serra, L. 2000.
Rapid Evolution of a Geographic Cline in Size in an Introduced Fly.
Science Vol. 287. no. 5451, pp. 308 – 309
This report discusses the evolution of wing size on a geographic cline in an
introduced population of Drosophila subobscura. A decade after being
introduced to North and South America D. subobscura showed no geographic
cline in wing size. However, after two decades there is a conspicuous cline
similar to that of the original Old World population indicating a rapid divergence in
wing size.
IPCC 1990. Climate change 1990: The scientific basis. Contribution of
Working Group 1 to the Fourth Assessment Report of the
Intergovernmental Panel on Climate Change. Cambridge University Press,
Cambridge, New York, USA.
This report highlights the current climate change science regarding greenhouse
gases (GHG), radiative forcing, patterns of precipitation, and extreme weather
events and makes future temperature, GHG, and weather related projections.
60% of the estimated increase in the level of radiative forcing from 1750 to 2000
can be attributed to increases in the levels of CO2. Oceans are projected to be
able to incorporate approximately 75% of anthropogenic CO2 emissions,
however, the fraction of CO2 taken up by both land and the oceans is expected to
decline with increasing CO2 concentrations.
IPCC. 2001. Climate change 2001: The scientific basis. Contribution of
Working Group 1 to the Third Assessment Report of the Intergovernmental
Panel on Climate Change. Cambridge University Press, Cambridge, New
York, USA.
This report highlights the current climate change science regarding greenhouse
gases (GHG), radiative forcing, patterns of precipitation, and extreme weather
events and makes future temperature, GHG, and weather related projections.
Burning of fossil fuels and land use change, such as deforestation, have
accounted for the majority of the 0.4% per year increase in CO2 concentrations
since 1980. Terrestrial uptake of anthropogenic CO2 is limited by the small
fraction of carbon that is able to be sequestered in wood and humus while the
rate of oceanic uptake is limited by the speed of vertical mixing.
Introduction: The Intergovernmental Panel on Climate Change (IPCC) was
established by the World Meteorological Organisation (WMO) and the United
Nations Environment Programme (UNEP) in 1988. The aim was, and remains, to
provide an assessment of the understanding of all aspects of climate change.
Including how human activities can cause such changes and can be impacted by
them. It had become widely recognized that human-influenced emissions of
green-house gases have the potential to alter the climate systems (see box 1),
with possible deleterious or beneficial effects. It was also recognized that
addressing such global issues required organization on a global scale, including
assessment of the understanding of the issue by the worldwide expert
communities.
IPCC. 2007. Climate change 2007: The scientific basis. Contribution of
Working Group 1 to the Fourth Assessment Report of the
Intergovernmental Panel on Climate Change. Cambridge University Press,
Cambridge, New York, USA.
This report highlights the current climate change science regarding greenhouse
gases (GHG), radiative forcing, patterns of precipitation, and extreme weather
events and makes future temperature, GHG, and weather related projections.
There has been a 35% increase in atmospheric CO2 over the past 250 years
from pre-industrial levels. Although land use is a factor in the current increase in
atmospheric CO2, the use of fossil fuels is the primary contributing source. The
intensity and frequency of extreme weather events has dramatically increased
during the past 50 years as a result of increased temperatures.
Jenkins, J.L., Powell, J.A., Logan, J.A., Bentz, B.J. 2001. Low seasonal
temperatures promote life cycle synchronization. Bulletin of Mathematical
Biology 63:573-595.
This paper modeled voltinism in the mountain pine beetle under different
temperature scenarios to determine if conditions exist for univoltine oviposition
cycles in the presence of discontinuities. Analysis was extended to include
quiescence during periods when temperatures drop below developmental
thresholds. From a mathematical modeling perspective, discontinuities are
created in the developmental map when these thresholds are crossed. Warming
due to climate change may result in asynchronous voltinism in some populations
and range expansion in others.
Abstract: In this paper we discuss how seasonal temperature variation and lifestage specific developmental thresholds that can cause quiescence can
synchronize the seasonal development of exothermic organisms. Using a simple
aging model it is shown that minimal seasonal temperature variation and periods
of quiescence during extreme temperature conditions are sufficient to establish
stable univoltine ovipositional cycles. Quiescence induced by life-stage specific
developmental thresholds, in fact, promotes synchronous oviposition and
emergence. The mountain pine beetle, an important insect living in extreme
temperature conditions and showing no evidence of diapause, invites direct
application of this model. Simulations using mountain pine beetle parameters are
used to determine temperature regimes for which stable ovipositional cycles
exist.
Jenkins, M.J., Hebertson, E., Page, W., Jorgersen, C.A. 2008. Bark beetles,
fuels, fire and implications for forest management in the Intermountain
West. Forest Ecology and Management. 254: 16-34.
This paper studied the effects of bark beetle infestations on tree mortality,
subsequent fuel accumulation, and resulting fire hazard in lodgepole pine,
Douglas-fir, and Englemann spruce. There is an increase in surface fire spread
and fire line intensity during bark beetle epidemics. Mortality due to bark beetles
alters dead fuel loads over time with high fuel loads at higher elevations
persisting for decades due to slower rates of decomposition.
Abstract: Bark beetle-caused tree mortality in conifer forests affects the quantity
and quality of forest fuels and has long been assumed to increase fire hazard
and potential fire behavior. In reality, bark beetles, and their effects on fuel
accumulation, and subsequent fire hazard, are poorly understood. We
extensively sampled fuels in three bark beetle-affected Intermountain conifer
forests and compared these data to existing research on bark beetle/fuels/fire
interactions within the context of the disturbance regime. Data were collected in
endemic, epidemic and post-epidemic stands of Douglas-fir, lodgepole pine and
Engelmann spruce. From these data, we evaluated the influence of bark beetlecaused tree mortality on various fuels characteristics over the course of a bark
beetle rotation. The data showed that changes in fuels over time create periods
where the potential for high intensity and/or severe fires increases or decreases.
The net result of bark beetle epidemics was a substantial change in species
composition and a highly altered fuels complex. Early in epidemics there is a net
increase in the amount of fine surface fuels when compared to endemic stands.
In post-epidemic stands large, dead, woody fuels, and live surface fuels
dominate. We then discuss potential fire behavior in bark beetle-affected conifer
fuels based on actual and simulated fuels data. Results indicated that for surface
fires both rates of fire spread and fireline intensities were higher in the current
epidemic stands than in the endemic stands. Rates of spread and fireline
intensities were higher in epidemic stands due, however, to decreased vegetative
sheltering and its effect on mid-flame wind speed, rather than changes in fuels.
Passive crown fires were more likely in post-epidemic stands, but active crown
fires were less likely due to decreased aerial fuel continuity. We also discuss the
ecological effects of extreme fire behavior. Information is presented on managing
forests to reduce the impact of bark beetle outbreaks and the interplay between
management, bark beetle populations, fuels and fire hazard and behavior.
Jentsch, A., Kreyling, J., Beierkuhnlein, C. 2007. A new generation of
climate-change experiments: Events, not trends. Frontiers in Ecology and
the Environment 5: 365-374.
This paper discusses weather such as extremely low temperatures, heavy
rainfall, and drought as extreme events not trends. Although frost hardening has
a dramatic effect on tolerance limits, cold injuries or minimum temperature effects
can be sudden and lethal. The ecotone shift resulting from extreme weather
events can remain for decades or longer even after climatic conditions stabilize.
Kimball, B.A., Idso, S.B., Johnson, S., Rillig, M.C. 2007. Seventeen years of
carbon dioxide enrichment of sour orange trees: Final results. Global
Change Biology 13: 1-13.
This was a free air CO2 enrichment experiment conducted over seventeen years
to determine the long-terms response of sour orange trees to elevated CO2.
Comparison of CO2 enriched and ambient trees showed that enriched trees
increased their biomass in branches, trunks large roots, and stumps 55%.
Biomass from leaves and twigs increased 20% while fruit production increased
200%. Overall biomass for enriched trees increased 70%.
Abstract: The long-term responses of trees to elevated CO2 are especially
crucial (1) to mitigating the rate of atmospheric CO2 increase, (2) to determining
the character of future forested natural ecosystems and their spread across the
landscape, and (3) to determining the productivity of future agricultural tree
crops. Therefore, a long-term CO2-enrichment experiment on sour orange trees
was started in 1987, and the final results after 17 years are reported herein. Four
sour orange trees (Citrus aurantium L.) were grown from seedling stage at 300
lmol mol_1 CO2 above ambient in open-top, clear-plastic-wall chambers at
Phoenix, AZ. Four control trees were similarly grown at ambient CO2. All trees
were supplied ample water and nutrients comparable with a commercial orchard.
After a peak 2–4 years into the experiment, there was a productivity plateau at
about a 70% enhancement of annual fruit and incremental wood production over
the last several years of the experiment. When summed over the duration of the
experiment, there was an overall enhancement of 70% of total biomass
production. Much of the enhancement came from greater numbers of fruits
produced, with no change in fruit size. Thicker trunks and branches and more
branches and roots were produced, but the root/shoot ratio was unaffected. Also,
there was almost no change in the elemental composition of the biomass
produced, perhaps in part due to the minimal responsiveness of root-symbiotic
arbuscular mycorrhizal fungi to the treatment.
Kittel, T.G.F., Rosenbloom, N.A., Painter, T.H., Schimel, D.S. 1995. The
VEMAP Integrated Database for Modelling United States
Ecosystem/Vegetation Sensitivity to Climate Change. Journal of
Biogeography, Vol. 22, No. 4/5, Terrestrial Ecosystem Interactions with
Global Change, Volume 2: 857-862.
This paper describes the development of a climate, soils, and vegetation
database compatible with three ecosystem physiology and three vegetation lifeform distribution models. Common boundary conditions and driving variables are
required to ensure that differences in modeling results were not from differences
in inputs. This was accomplished by defining vegetation types to address both
ecosystem physiological and vegetation life-form distribution models.
Körner, C. 1995. Towards a better experimental basis for upscaling plant
responses to elevated CO2 and climate warming. Plant Cell and
Environment 18: 1101-1110.
This paper discusses aspects of experimental work on plants and ecosystems
under future CO2 and temperature scenarios and the impact on the
discrepencies between theory and practice on real world up scaling. Results from
field studies of undisturbed vegetation often disagree with laboratory and growth
chamber studies. Synchronized plant start times produce a larger CO 2 response
in faster growing species not found in the field where growth and development
are not synchronized among plants of different species. The closer experiments
mirror complex plant interactions and field conditions the more relevant they
become.
Körner, C. 2000. Biosphere responses to CO2 enrichment. Ecological
Applications 10: 1590-1619.
This paper studied the carbon cycle, plant growth rate response, and water
relations under elevated CO2. Our example depicts only one cohort of trees all
growing in either a CO2 enriched or natural environment and reaching maturity at
a given size. Seedlings grown in growth chambers do not reflect natural
conditions and cannot be expected to mimic mature tree responses. The
predictive value of these experiments is uncertain due to their lack of
consideration for the complexity of real life interactions.
Körner, C. 2003. Carbon limitation in trees. Journal of Ecology 91: 4-17.
This paper studied the concentration of non-structural carbohydrates in trees
from four climatic zones as a measure of carbon shortage or surplus. The
continuous high abundance of NSCs and lipids, their increase towards the low
temperature tree limit, and the experimental data do not support the “carbon
limitation” hypothesis of treeline formation. At experimental concentrations of CO2
above 360-370 p.p.m. extra carbon was utilized for leaf and sapwood tissue and
not for structural growth indicating a high carbon loading of forests.
Körner, C., Asshoff, R., Bignucolo, O., Hättenschwiler, S., Keel, S.G.,
Peláez-Riedl, S., Pepin, S., Siegwolf, R.T.W., Zotz, G. 2005. Carbon flux and
growth in mature deciduous forest trees exposed to elevated CO2. Science
309:1360-1362.
This study used free air CO2 enrichment experiments over four years to
determine the impact of elevated CO2 on growth in a deciduous forest. Fagus
exposed to elevated levels of CO2 showed only a marginally significant response
over the four year study period. Data suggests that trees do not assimilate
carbon as structural material but “pump” it through in the form of leaves and
sapwood.
Kostyk, B.C., Borden, J.H., Gries, G. 1993. Photoisomerization of
antiaggregation pheromone verbenone: biological and practical
implications with respect to the mountain pine beetle, Dendroctonus
ponderosae Hopkins. Journal of Chemical Ecology 19: 1749–1759.
This paper discusses aerial application methods for verbenone and their effect
on the photoisomerization of verbenone during field experiments. The efficacy of
verbenone is affected by variations in environmental factors such as
temperature, relative humidity, precipitation and wind. Exposure to sunlight
photoisomerizes verbenone to chrysanthenone, which has no behavioral
influence on the response of mountain pine beetle to synthetic attractants.
Verbenone will photoisomerize more rapidly in southern locations and higher
elevations due to increased light intensity and a greater amount of UV light that
reaches the ground.
Kurz, W.A., Dymond, C.C., Stinson, G., Rampley, G.J., Neilson, E.T., Carroll,
A.L., Ebata, T. and Safranyik, L. 2008. Mountain pine beetle and forest
carbon feedback to climate change. Nature 452:987-990,
doi:10.1038/nature06777.
This study used the forest ecosystem model CBM-CFS3 to forecast the change
in net biome production in British Columbia forests for the period 2000-2020 due
to increased mountain pine beetle activity. The mountain pine beetle has
expanded its range in Canada due to an abundance of host trees and favourable
climate over the past several decades. Climate change can influence insect lifecycles as in the spruce beetle (Dendroctonus rufipennis Kirby) in north-western
North America where reproduction times have been cut in half due to warmer
temperatures.
Kurz, W.A., Apps, M.J. 1999. A 70-Year Retrospective Analysis of Carbon
Fluxes in the Canadian Forest Sector. Ecological Applications 9(2): 526547.
This study usednational forest inventory information, long-term records of forest
disturbance, and simulation modeling toanalyze the change in carbon storage in
Canadas forests from 1920-1989. The warmer temperatures experienced in
Canada during the 1980’s may have affected wildfire and insect disturbances as
well as biomass decomposition rates. The past two decades of the analysis
period have seen significant changes in the disturbance regime resulting in a
decrease in forest C sink and a release of C into the atmosphere.
Langenheim, J.H. 2003. Plant resins—chemistry, evolution, ecology, and
ethnobotany. Portland, Oregon: The Timber Press.
This is a book on the topic of plant resins in three parts; Resin Production which
gives biochemical, developmental, and systematic information, Geologic history
and Ecology of Resins which focuses on the question of resin production as
defense against herbivores and pathogens, and Ethnobotany of Resins.
Pinus ponderosa is the sole host for the western pine beetle (WPB) in California
and by selecting hosts based on monoterpene composition WPB can impose
significant selection pressure.
Little, E.L. 1971. Atlas of United States trees, vol. 1 Conifers and important
hardwoods. USDA Miscellaneous Publication 1146 Washington DC.
This is an atlas showing the distribution of the native tree species of the
continental United States including Alaska. Naturalized trees as well as trees
planted for forestry, shade, and other purposes have been omitted from the maps
of forest types. Maps do include geographic areas where species are native or
wild.
Llusià, J., Peñuelas, J. 1998. Changes in terpene content and emission in
potted Mediteranean woody plants under severe drought. Canadian
Journal of Botany 76: 1366-1373.
This paper studied the effects of increasing drought conditions on the
concentration and emission of terpenes in nine Medtierranean potted plants.
Plants accumulate carbon during periods of growth restriction caused by water
limitation which is then allocated to monoterpenes, storage, or to wood. When
exposed to drought stress the total terpene content of C. monseliensis increased
by 92.5%.
Logan, J.A., Amman, G.D. 1986. A distribution model for egg development
in mountain pine beetle. The Canadian Entomologist 118: 361-372.
This study used laboratory rearing at 7 different temperatures to develop a
model for egg development in the mountain pine beetle. The instar level is the
major determinant of mortality during overwintering in the mountain pine beetle.
Life stage distribution is a result of individual developmental rates and timing of
ovipositional distribution both of which are temperature dependent.
Abstract: Mountain pine beetle (Dendroctonus ponderosae Hopkins) population
dynamics, as well as potential for outbreaks and resulting tree mortality, are
related in part to habitat temperature. As a first step in development of a lifestage, event-oriented simulation model, we have modeled the temperaturedependent development of the egg stage. The completed model includes a full
description of variation in developmental rated and is capable of predicting
duration and eclosion patterns for any temperature regime. This model was
parameterized using data obtained from constant-temperature experiments at
temperatures of 8, 10, 12.5, 15, 20, 25, and 30˚C. Validation experiments were
conducted for constant temperatures of 15, 17.5, 22.5, and 27.5˚C and for
variable-temperature regimes of 15±5 and 15±10˚C. Validation results indicated
that the model is capable of accurately describing the emergence curve for
constant temperatures below 27.5˚C. The model also faithfully represents
emergence under variable temperatures of 15±10˚C. Potential reasons for lack
of model fidelity in describing emergence at constant high temperatures and for
15±5˚C are discussed in the text.
Logan, J.A., Bentz, B.J. 1999. Model analysis of mountain pine beetle
(Coleoptera: Scolytidae) seasonality. Environmental Entomology 28: 924–
934.
This paper used modeling to determine if adaptive univoltism is an emergent
property in the mountain pine beetle. Developmental rates are sensitive not only
to thermal input, but the seasonal timing and pattern of the inputs. Diapause is
found in the life-cycle of most insects and is used to achieve synchrony. The
mass attack strategy utilized by the mountain pine beetle relies on synchrony of
emerging adults without diapause known as adaptive seasonality.
Abstract: The mountain pine beetle, Dendroctonus ponderosae Hopkins, is a
natural disturbance agent of considerable consequence in western pine forests.
This economically and ecologically important insect has a strong requisite for
maintaining a strict seasonality. Given this ecological requirement, it is
somewhat surprising that no evidence for diapauses or other physiological timing
mechanism has been found. Seasonality and phenological timing for this
species are apparently under direct temperature control. We investigate the
consequences of direct temperature control by first constructing a
computationally efficient phenology model based on previously published
temperature dependent developmental data. We explored the dynamic
properties of this model when subjected to observed microhabitat temperatures
representing a range of thermal habitats from one region of the mountain pine
beetle distribution. We also investigated the consequences of global climate
change on phenology and seasonality. Our results indicate that an adaptive
seasonality is a natural consequence of the interaction between developmental
parameters and seasonal temperatures. Although this adaptive phenology
appears to be resilient to temperature fluctuations, changes in climate within the
magnitude of predicted climate change under a CO2 doubling scenario are
capable of shifting a thermally hostile environment to a thermally benign
environment. Similarly, increasing temperature by the same amount resulted in
phonological disruption of a previously favorable thermal habitat. We discuss the
implications of these results for restricting the current distribution of mountain
pine beetle, and the potential for shifting distribution caused by global climate
change.
Logan, J.A., Powell, J.A. 2001. Ghost forests, global warming, and the
mountain pine beetle. American Entomologist. 47: 160-73.
This paper discusses mountain pine beetle ecology, adaptive seasonality,
development of a phenology model, and management strategies for mountain
pine beetles and invasive species. Mountain pine beetles do not undergo
diapause which is crucial in maintaining adaptive seasonality in most insects but
are under direct temperature control. The model predicts that small increases in
the mean temperature can result in asynchrony and a subsequent change in
voltinism.
Abstract: The mountain pine beetle, Dendroctonus ponderosae Hopkins, is a
significant ecological force at the landscape level. The majority of the life cycle is
spent as larvae feeding in the phloem tissue (inner bark) of host pine trees. This
feeding activity eventually girdles and kills successfully attacked trees (Amman
and Cole 1983, Furniss 1997). Outbreaks of this insect can be truly spectacular
events (Fig. 1A; Amman and Logan 1998). Most western pines are suitable hosts
for this insect, but ponderosa pine, Pinus ponderosae Lawson, and lodgepole
pine, Pinus contorta Douglas, currently are the most important host species. The
distribution of the beetle generally reflects this primary host range, although
lodgepole pine extends further north and ponderosa pine extends further south
than the current geographic range of the beetle. The mountain pine beetle is a
native insect, having co-evolved as an important ecological component of
western pine forests. The inter-relationship between beetle-caused mortality and
subsequent fire has resulted in a basic ecological cycle for many western forests
(Schmidt 1988). Some pines species, such as lodgepole pine, are maintained by
periodic disturbances. The lodgepole pine forest-type1 typically is an essential
monoculture of even-aged trees that were initiated by a catastrophic, standreplacing fire. Without the influence of fire (Fig. 1B), lodgepole pine would be
lost over much of its native range (Brown 1975, Lotan et al. 1985). Fire serves to
prepare the seedbed, releases seeds from the serotinous cones (triggered
to release seeds by heat of a fire), and eliminates more shade-tolerant species
such as spruce or fir that would eventually out-compete and replace the early
seral lodgepole pine.
Logan, J.A., Regniere, J., Powell, J.A. 2003. Assessing the impact of
global warming on forest pest dynamics. Frontiers in Ecology and the
Environment 1:130–137.
This paper discusses the potential impact of climate change driven altered
disturbance regimes on forest insect populations and forest ecology. The effect
of temperature on population growth rates, synchrony, and geographic
distribution must be assessed individually for each species. Modeling shows that
seasonal biological cycles will be attracted to a stable point within a few
generations.
Abstract: Forest insects and pathogens are the most pervasive and important
agents of disturbance in North American forests, affecting an area almost 50
times larger than fire and with an economic impact nearly five times as great. The
same attributes that result in an insect herbivore being termed a “pest”
predispose it to disruption by climate change, particularly global warming.
Although many pest species have co-evolved relationships with forest hosts that
may or may not be harmful over the long term, the effects on these relationships
may have disastrous consequences. We consider both the data and models
necessary to evaluate the impacts of climate change, as well as the assessments
that have been made to date. The results indicate that all aspects of insect
outbreak behavior will intensify as the climate warms. This reinforces the need
for more detailed monitoring and evaluations as climatic events unfold. Luckily,
we are well placed to make rapid progress, using software tools, databases, and
the models that are already available.
Logan, J.A., Regniere, J., Gray, D.R., Munson, A.S. 2007. Risk assessment
in the face of a changing environment: gypsy moth and climate change in
Utah. Ecological Applications 17(1): 101-17.
This paper discussed the probability of anthropogenically assisted range
expansion and evaluated the risk for establishment of the gypsy moth after
introduction into new habitat. Landscape maps of the gypsy moth establishment
hazard were producued using the BioSIM system. After running the model for 10
generations with weather related driving variables a probability for adaptive
seasonality was determined.
Abstract: The importance of efficaciously assessing the risk for introduction and
establishment of pest species is an increasingly important ecological and
economic issue. Evaluation of climate is fundamental to determining the
potential success of an introduced or invasive insect pest. However, evaluating
climatic suitability poses substantial difficulties as climate can be measured and
assed in a bewildering array of ways. Some physiological filter, in essence a
lens that focuses climate through the requirements and constraints of a potential
pest introduction, is required. Difficulties in assessing climate suitability are
further exacerbated by the effetcts of climate change.
Gypsy moth (Lymantria dispar L.) is an exotic, tree-defoliating insect that is
frequently introduced into the western United States. In spite of an abundance of
potential host species, these introductions have yet to result in established
populations. The success of eradication efforts and the unsuccessful
establishment of many detected and undetected introductions may be related to
an inhospitable climate. Climatic suitability for gypsy moth in the western United
States, however, is potentially improving, perhaps rapidly, due to a general
warming trend that began in the mid 1970s and continues today. In this work, we
describe the application of a physiologically based climate suitability model for
evaluating risk of gypsy moth establishment on a landscape level.
Development of this risk assessment system first required amassing databases
that integrated the gypsy moth climatic assessment model, with host species
distributions, and climate (historical, present, and future). This integrated system
was then used to evaluate climate change scenarios for native host species in
Utah, with the result that risk of establishment will dramatically increase during
the remainder of the 21st century under reasonable climate change scenarios.
We then applied the risk assessment system to several case histories of
detected gypsy moth introductions in Utah. These applications demonstrated the
general utility of the system for predicting risk of establishment and for designing
improved risk detection strategies.
Lombardero, M.J., Ayers, M.P., Lorio, Jr., P.L., Ruel, J.J. 2000.
Environmental effects on constitutive and inducible resin defenses of
Pinus taeda. Ecology Letters 3: 329-339.
This study compared the effects of fertilization, seasonal drought, and crown size
on constitutive and inducible resin defenses in loblolly pine. Plants with strong
internal regulation have inducible responses that are determined by plant
genotype and environmental stimulus (wounding). Increases in oleoresin
production may decrease bark beetle attack rates, adult survival, oviposition
success, and larval survival. After wounding, resin flow doubled within seven
days with most of the increase occurring within the first three days.
Abstract: The ecological literature abounds with studies of environmental effects
on plant antiherbivore defenses. While various models have been proposed (e.g.
plant stress, optimal allocation, growth-differentiation balance), each has met
with mixed support. One possible explanation for the mixed results is the
constitutive and induced defenses are differentially affected by environmental
conditions. In this study, constitutive oleoresin flow from Pinus tadea was least
during periods of rapid tree growth and most when drought conditions limited
growth; this is as expected if constitutive secondary metabolism is a function of
the carbohydrate pool size after growth has been maximized. Induced increases
in resin flow, however, were greatest in the fastest growing trees during the
season of greatest growth. Apparently, resin production becomes an allocation
priority after wounding but not before. Understanding environmental effects on
plant antiherbivore defenses requires physiological and evolutionary models that
account for the differences between constitutive and induced secondary
metabolism.
Lotan, J.E., Brown, J.K., Neuenschwander, L.F. 1985. Role of fire in
lodgepole pine forests. Pp. 133-152. In: D.M. Baumgarner, D.M., Krebill,.
Lodgepole pine: The Species and its Management. May 1984, Spokane, WA
and Vancouver, BC. Washington State Cooperative Extension, Pullman,
WA.
This paper discusses the role of bark beetles in mortality and fuel buildup, fire
frequency, forest succession, and regeneration cycle in lodgepole pine forests.
Drought, insects and wildfire are naturally occurring disturbances that shape
Colorado’s forests. Warming trends can make fuel extremely dry and fires
intense and difficult to control which can be costly to life, property, and water
supplies. Warmer temperatures have allowed the mountain pine beetle to expand
its elevational range.
Lucht, D.D., Frye, R.H., Schmid, J.M. 1974. Emergence and attack behavior
of Dendroctonus adjunctus Blandford near Cloudcroft, New Mexico. Annals
of Entomological Society America 67: 610-612.
This study used attacked, caged ponderosa pine trees to determine voltinism and
emergence patterns in the roundheaded pine beetle (Dendroctonus adjunctus
Blandford). D. adjunctus is primarily a univoltine species, with about 7%
semivoltine brood emergence occurring during October and November. Attacks
that occur in the spring are most likely re-emerging adults or adults that failed to
emerge in the fall.
Abstract: We examined the historical record of mountain pine beetle
Dendroctonus ponderosae Hopkins) activity within Yellowstone National Park,
Wyoming, for the 25-years period leading up to the 1988 Yellowstone fires
(1963–86) to determine how prior beetle activity and the resulting tree mortality
affected the spatial pattern of the 1988 Yellowstone fires. To obtain accurate
estimates of our model parameters, we used a Markov chain Monte Carlo
method to account for the high degree of spatial autocorrelation inherent to forest
fires. Our final model included three statistically significant variables: drought,
aspect, and sustained mountain pine beetle activity in the period 1972–75. Of the
two major mountain pine beetle outbreaks that preceded the 1988 fires, the
earlier outbreak (1972–75) was significantly correlated with the burn pattern,
whereas the more recent one (1980–83) was not. Although regional drought
and high winds were responsible for the large scale of this event, the analysis
indicates that mountain pine beetle activity in the mid-1970s increased the
odds of burning in 1988 by 11% over unaffected areas. Although relatively small
in magnitude, this effect, combined with the effects of aspect and spatial variation
in drought, had a dramatic impact on the spatial pattern of burned and unburned
areas in 1988.
Luxmoore, R.J., Oren, R., Sheriff, D.W., Thomas, R.B. 1995. Source–sink–
storage relationships of conifers. pp. 179-216. In: W.K. Smith, W.K.,
Hinckley, T.M. (eds.), Resource Physiology of Conifers. Academic Press,
San Diego, CA.
This paper summarizes examples of carbon assimilation and utilization
responses, and examines the source-sink-storage interaction at the leaf and tree
scales. Pseudotsuga menziesii seedlings transported more carbohydrates to root
growth during the month of November than in May. Loblolly pine with high foliar
N content used starch reserves earlier in the growing season. Although growth
and photosynthesis are interconnected, growth is more sensitive to water and/or
nutrient deficiencies.
Abstract: Irradiance, air temperature, saturation vapor pressure deficit, and soil
temperature vary in association with Earth’s daily rotation, inducing significant
hourly changes in the rates of plant physiological processes. These processes
include carbon fixation in photosynthesis, sucrose translocation, and carbon
utilization in growth, storage, and respiration. The sensitivity of these
physiological processes to environmental factors such as temperature, soil water
availability, and nutrient supply reveals differences that must be viewed as an
interactive whole in order to comprehend whole-plant responses to the
environment. Integrative frameworks for relationships between plant
physiological processes are needed to provide syntheses of plant growth and
development. Source-sink-storage relationships, addressed in this chapter,
provide one framework for synthesis of whole-plant responses to external
environmental variables.
To address this issue, some examples of carbon assimilation and utilization
responses of five conifer species to environmental factors from a range of field
environments are first summarized. Next, the interactions between sources,
sinks, and storages of carbon are examined at the leaf and tree scales, and
finally, the review evaluates the proposition that processes involved with carbon
utilization (sink activity) are more sensitive to the supply of water and nutrients
(particularly nitrogen) than are the processes of carbon gain (source activity) and
carbon storage. The terms “sink” and “source” refer to carbon utilization and
carbon gain, respectively. The physiological processes determining these are
referred to as “sink activity” (carbon storage, tissue growth) and “source activity”
(photosynthesis), as appropriate. The relative roles of stored carbon reserves
and of current photosynthate in meeting sink demand are addressed. The
activities and vigor of various sources and sinks of a species (including
symbionts) depend on the microclimate of a plant or organ and on seasonal
changes in climate (Cannell 1985, 1989). Discussions focus on source-sinkstorage relationships within the diurnal, wetting-drying, and annual cycles of
conifer growth and development, and some discussion of life cycle aspects is
also presented.
Lynch, H.J., Renkin, R.A., Crabtree, R.L., Moorcroft, P.R. 2006. The
influence of previous mountain pine beetle (Dendroctonus ponderosae)
activity on the 1988 Yellowstone fires. Ecosystems 9: 1318-1327.
This study used three important variables, drought, aspect, and sustained
mountain pine beetle (MPB) activity to determine how prior MPB activity
influenced the 1988 Yellowstone fires. The two 1988 Yellowstone fire study areas
showed a marked difference in their risk of burning. In the 1972-1975 MPB
outbreak area there was an 11% increase while the 1980-1983 outbreak area
was not correlated with an increased log odds of burning. Results indicate that
secondary effects such as stand composition and structure increase fire risk far
greater than primary effects.
Magnani, F., Consiglio, L., Erhard, M., Nole, A., Ripullone, F., Borghetti, M.
2004. Growth patterns and carbon balance of Pinus radiata and
Pseudotsuga menziessii plantations under climate change scenarios in
Italy. Forest Ecology and Management 202:93–105.
This paper evaluated the HYDRALL model by comparing predicted forest growth
under current conditions with stem data and then simulated growth patterns,
carbon balance, and water use efficiency under climate change scenarios. P.
menziesii and P. radiata both showed an increase in WUE in the Brasimone
simulation. The positive impacts of the CO2 fertilisation effect could be offset by
other aspects of climate change such as drought.
Maherali, H., DeLucia, E.H. 2000. Interactive effects of elevated CO2 and
temperature on water transport in ponderosa pine. American Journal of
Botany 87: 243-249.
This experiment studied ponderosa pine seedlings grown under four different
levels of atmospheric CO2 and two temperatures to determine if growth in
elevated CO2 affects the hydraulic conductivity and biomass allocation of
ponderosa pine. The biomass allocation to xylem and leaves combined with the
specific hydraulic conductivity of the xylem determines the leaf specific hydraulic
conductivity. Our results indicate an increase in water transport capacity in
ponderosa pine due to elevated temperature and atmospheric evaporative
demand.
Maherali, H., Williams, B.L., Paige, K.N., DeLucia, E.H. 2002. Hydraulic
differentiation of ponderosa pine populations along a climate gradient is
not associated with ecotypic divergence. Functional Ecology 16: 510-521.
This study employed a common garden experiment to determine if populations of
ponderosa pine from desert and montane climate groups diverged from each
other under drought treatment versus watering to field capacity every other day.
In this study drought conditions had no effect on the root to shoot ratio. A
reduction in the leaf to sapwood ratio which increases leaf specific hydraulic
conductance allows transpiration without inducing cavitation which can result in
death.
Martin, D., Gershenzon, J. Bohlmann, J. 2003. Induction of volatile terpene
biosynthesis and diurnal emission by methyl jasmonate in foliage of
Norway spruce (Picea abies). Plant Physiology 132: 1586–1599.
This paper studied the effects of methyl jasmonate treatments on the terpene
synthase activity, terpene content, and terpene emissions in Norway spruce
needles. After treatment with methyl jasmonate, Norway spruce needles
experienced a 5-fold increase in monoterpene and sesquiterpene synthesis.
Evidence indicates that these terpenes are synthesized de novo. Volatilization of
terpene synthase assay products prevented their accumulation in the needles.
Martin, D., Tholl, D., Gershenzon, J., Bohlmann, J. 2002. Methyl jasmonate
induces traumatic resin ducts, terpenoid resin biosynthesis, and terpenoid
accumulation in developing xylem of Norway spruce stems. Plant
Physiology 129: 1003–1018.
This experiment used a topical application of methyl jasmonate to study the
induced formation of traumatic resin ducts in Norway spruce. Resin duct lumens
began to develop in the xylem within 15 days after treatment with methyl
jasmonate. Treatment levels of 10 mM were most effective in increasing both
monoterpene and diterpene synthase activity. Monoterpene synthase activity in
the wood increased 28-fold by day 9 and remained at higher levels than the
control until day 35.
Masaki, S. 1967. Geographic variation and climatic adaptation in a field
cricket (Orthoptera: Gryllidae). Evolution 21: 725-741.
This paper discusses possibility of climatic selection as the likely cause of the
geographic cline in the size of the Emma field cricket. Head width is directly
related to body sixe in the Emma field cricket and declines from south to north
and from lower to higher altitudes. This indicates that temperature, which varies
with both latitude and altitude, has a major influence on development and
selection. This north south cline reflects selections for adjustments of
development time that parallel growing seasons allowing for complete utilization
of resources.
Masaki S. 1973. Climatic adaptation and photoperiodism in the band-legged
cricket. Evolution 261:587-600.
This study was a laboratory experiment designed to test the effects of varied
photoperiods on voltinism and the correlation between development time and
adult size. A shorter photoperiod during nymphal development had a retarding
effect on maturation times with an increased effect on populations from higher
latitudes. There is a transitional area between 36˚ N and 38˚ N where slowgrowing and fast-growing populations show two separate peaks of retardation
resulting in bivoltine and univoltine life cycles.
Mattson, W.J., Jr. 1980. Herbivory in relation to plant nitrogen content.
Annual Review of Ecology and Systematics 11: 119-161.
This is a review of the evidence that in response to limited metabolizable nitrogen
herbivores have evolved behavioral, morphological, and physiological
adaptations to utilize the available nitrogen. At the height of the growing season
Heteromeles arbutifolia allocated most of its fixed carbon resources to growth
and only small amounts of carbon to phenolic synthesis. Plants in N poor soils
may possess an abundance of photosynthates and be growth limited.
Mattson, W.J. Jr., Addy, N.D. 1975. Phytophagous insects as regulators of
forest primary production. Science 90: 515–522.
This study measured the intensity of grazing, quantity and distribution of
photosynthetic biomass, and variations in photosynthetic rates to evaluate the
effects of grazing by insects on primary production. Plants and insects have
coevolved to exhibit intricate and intensive interactions in response to each other.
Insects are sensitive to changes in host quality such as aging, water stress, and
nutrient deficiencies resulting in an inverse relationship between forest vigor and
insect populations.
Mattson, W.J., Haack, R.A. 1987. The role of drought in outbreaks of planteating insects. BioScience 37: 110–118.
This paper discusses some of the mechanisms by which drought affects insect
behavior and physiology such as a more favorable developmental environment,
increasing host susceptibility, and lower numbers and decreased virulence of
predators and parasites. Studies have shown that insects developing under
optimum temperatures grow faster and larger and experience an increased
fecundity. Insect chemoreceptors are sensitive to changes in chemical blends
that make drought stressed plants more attractive.
Mattson, W.J. Jr., Niemela, P., Rousi, M. 1996. Dynamics of Forest
Herbivory: Quest for Pattern and Principle. GTR-NC-183. U.S. Department
of Agriculture, Forest Service, North Central Research Station, St. Paul,
MN, 286 pp.
This publication is a series of symposium presentations relating to plantherbivore interactions and climate change. Tree spacing and stand diversity are
important factors in limiting and controlling insect populations. Resistance to bark
beetle attack depends on the terpene composition of the oleoresin. Exudation
rates can be low, intermediate, or high depending upon the pine species.
McCambridge, W.F., Knight F.B. 1972. Factors affecting spruce beetles
during a small outbreak. Ecology. 53: 830-839.
This study used cages on both trap and live trees to determine the voltinism of
spruce beetle broods collected from the 1957 outbreak in north-central Colorado.
Through, it was established that most beetles emerged on normal 1- and 2-year
life cycles, although some emerged on 3-year cycles. Fourteen percent of adults
collected were under the bark for 3 years, but not suspected to be on 4-year
cycle, though that possibility is not excluded as impossible.
McCarty, J.P. 2001. Ecological consequences of recent climate change.
Conservation Biology 15: 321-331.
This paper is a review of documented changes in ecosystems and in the
phenology of a number of species as a result of climate change. 60 years of
nesting data collected in the UK showed that 78% of the 65 species studied had
breeding dates that were on average 9 days earlier for the period 1971 to 1995.
As a result of climate change local species may face an increased risk of
extinction at the same time that habitat becomes more suitable for invasive and
exotic species.
McFarlane, N.A., G.J. Boer, J.P. Blanchet, and M. Lazare. 1992. The
Canadian climate centre second-generation general circulation model and
its equilibrium climate. Journal of Climate 5:1013-1044.
This paper decribes the GCMII general circulation model and some features of
the simulation of the current climate. The atmospheric general circulation model
(GCMII) adjusted the way that humidity, clouds, radiation, and surface processes
over land and sea ice were treated. The GCMII is able to simulate the current
climate reasonably well, an indication of its suitability for studying climate
variability and sensitivity.
McKenney, D.W., Pedlar, J.H., Lawrence, K., Campbell, K., Hutchinson, M.F.
2007. Potential impacts of climate change on the distribution of North
American trees. Bioscience 57: 939-948.
This is a detailed study of the potential impacts of climate change on the climatic
ranges of 130 species of trees on the North American continent. Climate
envelope richness will change drastically as climate change forces a northward
migration of suitable habitat. Assisted migration and forest regeneration policies
may have to be implemented as a result of rapid ecotone shifts and slow
colonization of many tree species.
McNulty, S.G., Aber, J.D. 2001. US National Climate Change Assessment
on Forest Ecosystems: An Introduction. BioScience. 51: 720–722
This paper discusses the impact of climate change on forest processes,
biodiversity change, disturbance interactions, and socioeconomic change. Initial
increases in productivity resulting from climate change may increase fuel loads
which combined with drought will potentially increase the area of forest burned in
the future by 25%-50%. When stressors such as changes in fire frequency and
ozone are included in the analysis, some regions may experience a reduction in
productivity of greater than 20%.
Abstract: Atmospheric concentrations of carbon dioxide (CO2) and other
greenhouse gases have been increasing since the beginning of the industrial
revolution in 1850. Over the next century, increasing gas concentrations could
cause the temperature on the surface of the Earth to rise as much as 2–3°C over
historic mean annual levels. Variation in annual climate could also increase. The
United States experienced one indication of climate change in 1988: The
summer of that year was one of the hottest, driest ever recorded across the
nation. Barges were stranded on the Mississippi River, and forest fires burned
millions of acres in the western United States. In the eastern United States,
temperatures were so high that many factory assembly lines had to be shut
down. The former Soviet Union states and China also experienced severe
drought, while Africa, India, and Bangladesh witnessed torrential rains and
flooding. These events triggered televised congressional debates, which
concluded that atmospheric greenhouse gas inputs would very likely increase the
intensity and severity of weather patterns during the next 100 years. The
potential negative effects of global warming—melting of polar ice caps, a rise in
the sea level, reduced agricultural and forest productivity, water shortages, and
extinction of sensitive species were also discussed. These findings prompted the
passage of the 1990 Global Change Research Act (GCRA) and the
establishment of the US Global Change Research Program (USGCRP). The
program sponsors ongoing research (over $1.6 billion in 2000) at several federal
agencies, including the National Aeronautics and Space Administration,
Department of Energy, US Department of Agriculture, Environmental Protection
Agency, National Institutes of Health, Department of Commerce, and National
Science Foundation, among others (USGCRP 1999). In addition to providing a
mechanism for funding research on global change, the GCRA mandates that an
assessment be conducted periodically to summarize research findings. Begun in
1997, the first National Assessment of the Potential Consequences of Climate
Variability and Change was published in 2001 (USGCRP 2001). The assessment
was a collaboration between federal and nonfederal researchers, resource
managers, and users. The assessment is divided into five sectors: (1) water
resources and availability, (2) agriculture and food production, (3) human health,
(4) coastal areas, and (5) forests. These sectors represent important or
potentially sensitive US resources that could be adversely affected by climate
change. The assessment also includes over 20 regional studies, which examine
the impacts of climate change for specific geographical areas of the United
States. This special section of BioScience focuses on a summary of research
findings from the forest sector and regional findings of the 2001 national
assessment (USGCRP 2001). The impacts of climate change on the forest
sector are divided into four categories: (1) forest processes, (2) biodiversity
change, (3) disturbance interactions, and (4) socioeconomic change. These
categories represent key interactions between a changing climate, forest
structure or function, and human interactions with forests.
Mearns L.O. 2003. Issues in the impacts of climate variability and change
on agriculture - Applications to the southeastern United States. Climatic
Change 60(1-2): 1-6.
This is an editorial focusing on a set of six papers collectively addressing the
interaction of agriculture with climate variability and change in the southeastern
United States. The BHI has a stronger correlation with local daily maximum and
minimum temperatures and daily precipitation than does ENSO. In areas of
complex land use or regions with mountainous areas or complex coastlines a
high resolution scenario may provide more realistic responses to changes in
forcing.
Millard, P., Sommerkorn, M., Grelet, G-A. 2007. Environmental change and
carbon limitation in trees: A biochemical, ecophysiological and ecosystem
appraisal. New Phytologist 175: 11-28.
This study examines the evidence for C limitation in the photosynthetic response,
C storage and nutrient cycling, and ecosystem responses of trees to elevated
CO2. Much of the soluble C is abscised with leaf shedding while nutrients held in
the leaves are reused. Trees also transfer C to root symbionts and benefit from
microbial activity and nutrient acquisition and cycling. This indicates that growth
in trees may be nutrient limited rather than C limited.
Millennium Ecosystem Assessment. 2003. Ecosystems and Human WellBeing. Island Press, Washington D.C.
This is a report on current and future conditions and trends of ecosystems and
their relation to human well-being and suggested responses, actions, and
processes that may be utilized to aviod or realize specific futures. Ecosystem
goods and services include products such as food, fresh water, biochemicals,
fiber, and genetic resources. They also include nonmaterial benefits to humans
such as religous or spiritual meaning,recreation,educational, or cultural heritage.
There is also support activities like soil formation, nutrient cycling, and primary
production.
Miller, J.M., Keen, F.P. 1960. Biology and control of the western pine
beetle: A summary of the first fifty years of research. USDA Forest Service
Misc. Publ. 800.
This book contains biology, life-history, and developmental information on
Dendroctonus brevicomis through 1960. Prepupal western pine beetle larvae
hatch in the outer bark and migrate in towards the phloem. However, beginning
with instar II through instar IV, larvae migrate back to the outer bark, where they
form an enlarged gallery in which to pupate. Adult beetles perform optimally at
temperatures of 70 - 85°F although extraneous weather events can completely
prevent or dictate pattern of flight.
Miller, L.K., Werner, R.A., 1987. Cold-hardiness of adult and larval spruce
beetles Dendroctonus rufipennis (Kirby) in interior Alaska. Canadian
Journal of Zoology 65, 2927-2930.
This purpose of this study was to determine if Dendroctonus rufipennis is
freezing tolerant or freezing susceptible in larval and adult stages and what
seasonal physio-chemical changes occur related to cold-hardiness. The super
cooling point for spruce beetles in larval and adult stages ranged from -12°C
during the summer to -30°C in the winter. Survival rates were not affected by
exposure to temperatures within 1-4°C of the super cooling point. Prolonged
severe cold, light snowfall, or hibernating near or above the snowline decreases
overwinter survival in D. rufipennis.
Mondor, E.B., Tremblay, M.N., Awmack, C.S., Lindroth, R.L. 2004.
Divergent pheromone-mediated insect behaviour under global atmospheric
change. Global Change Biology 10: 1820–1824.
This study assessed the effects of elevated levels of CO2 and O3 on pheromone
mediated dispersal behavior in Chaitophorus stevensis. Changing atmospheric
conditions and increases in greenhouse gases may radically alter intraspecific
olfactory communication which may impact the abundance and distribution of
many species. The response in aphids to alarm pheromone increased under
elevated O3 and decreased in response to elevated CO2.
Moore, D.J.P., Aref, S., Ho, R.M., Pippen, J.S., Hamilton, J.G., DeLucia, E.H.
2006. Annual basal area increment and growth duration of Pinus taeda in
response to eight years of free-air carbon dioxide enrichment. Global
Change Biology 12: 1367-1377.
This paper studied the long-term effects of elevated CO2 on the variation in
interannual growth of Pinus taeda and to determine if the increase in basal area
is sustained over time. Photorespiration increases faster than photosynthesis at
higher temperatures resulting in less carbon gain for P. taeda. Carbon fixed by
contrasting forest types will be allocated differently. Some will experience
increased stem growth while others will allocate additional carbon to fine root
development.
Moser, J.C., Fitzgibbon, B.A., Klepzig, K.D. 2005. The Mexican pine beetle,
Dendroctonus maxicanus: first recorded in the United States and cooccurrence with the southern pine beetle - Dendroctonus frontalis
(Coleoptera: Scolytidae or Curculionidae: Scolytinae). Entomological News.
116(4): 235-243
This paper chronicles the range expansion of Dendroctonus maxicanus and cooccurance with Dendroctonus frontalis in the Coronado National Forest in
Arizona. It is unclear if these two species have co-occurred for some time in this
area, have recently invaded or were introduced by log transport. At the Turkey
Creek trap site Mexican pine beetle outnumbered southern pine beetle 34:1 and
males outnumbered females 10:1.
Abstract: The Mexican pine beetle (XPB) Dendroctonus mexicanus, is recorded
here for the first time as a new introduction for the United States (US). Individuals
of XPB and its sibling species, the southern pine beetle (SPB) Dendroctonus
frontalis, were found infesting the same logs of Chihuahua pine, Pinus leiophylla
var. chihuahuana and those of several other pine species in the
Chiricahua Mountains, AZ. Both species were also captured in Lindgren traps
baited with southern and western pine beetle attractants, both of which contained
the pheromone frontalin. XPB outnumbered SPB 16:1 in the traps. Both XPB and
SPB were trapped during warm periods in winter. It is possible that XPB attack
trees during winter as SPB do in the southeastern US. Both XPB and SPB are
highly destructive to pines, and XPB could pose a threat if accidentally
introduced to pines in the higher elevations of the eastern US.
Mueller, R.C., Scudder, C.M., Porter, M.E., Trotter, III, R.T., Gehring, C.A.,
Whitham, T.G. 2005. Differential tree mortality in response to severe
drought: Evidence for long-term vegetation shifts. Journal of Ecology 93:
1085-1093.
This study examined the impact of repeated severe drought on tree mortality in
pinyon-juniper woodlands in the southwestern United States. Prolonged periods
of drought can result in xylem cavitation and mortality in larger trees due to
higher water use per unit of time than smaller trees. Pinyon mortality from severe
drought can alter community structure and eliminate some species such as seed
dispersing birds and microbial decomposers.
Nebeker, T.E., Hodges, J.D., Blanche, C.A. 1993. Host response to bark
beetle and pathogen colonization. Pgs. 157–173, In: Schowalter, T.D., Filip,
G.M. (eds.), Beetle-Pathogen Interaction in Conifer Forests, Academic
Press, London.
This paper discusses constitutive conifer defenses against bark beetle attack
such as resin chemistry and resin flow and inducible defenses such as
secondary resinosis, tissue necrosis, and formation of wound periderm. The
induced defense system in conifers includes localized autolysis and desiccation
of parenchyma cells, tissue necrosis, secondary resinosis, and lesion isolation
through the formation of wound periderm. The induced hypersensitive response
and lesion size are both positively correlated with temperature. Tree vigor may
play an important role in wound isolation and infection containment.
Negrón, J. 1997. Estimating probabilities of infestation and extent of
damage by the roundheaded pine beetle in ponderosa pine in the
Sacramento Mountains, New Mexico. Canadian Journal of Forest Research
27: 1634-1645.
This study used stand and tree characteristics preferred by the roundheaded
pine beetle to develop probability of infestation and extent of mortality models for
management use in the Sacramento Mountains. Forests with high basal area of
ponderosa pine combined with poor growth for the previous 5 years are at high
risk for roundheaded pine beetle infestation. Forests in the southwestern U.S.
have seen a decrease in the number of ponderosa pine and an increase in white
fir. An increase in density, growing stock and number of large diameter trees may
make these stands more prone to insect outbreaks.
Abstract: Classification trees and linear regression analysis were used to build
models to predict probabilities of infestation and amount of tree mortality in terms
of basal area resulting from roundheaded pine beetle, Dendroctonus adjunctus
Blandford, activity in ponderosa pine, Pinus ponderosa Laws., in the Sacramento
Mountains, New Mexico. Classification trees were built for combined habitat
types sampled and for each habitat type series or type sampled. Cross-validation
estimates of classification accuracy ranged from 0.64 to 0.79. The data suggest
that stands attacked by the roundheaded pine beetle exhibit poor growth during
the last 5 years prior to attack, abundant host type, and smaller diameter than
uninfested stands. Trees prone to attack by the roundheaded pine beetle within
infested points also exhibited reduced growth rates and smaller diameters than
uninfested trees. Linear regression analysis indicates that initial amount of
ponderosa pine basal area is a good predictor variable for the amount of basal
area affected.
Negrón, J.F., Popp, J.B. 2004. Probability of ponderosa pine infestation by
mountain pine beetle in the Colorado front range. Forest Ecology and
Management 191: 17-27.
This study modeled the probability of mountain pine beetle infestation in the
Colorado Front Range to develop a hazard rating for potential infestations.
Grazing and fire suppression in forest ecosystems has resulted in increased
stand densities and fuel loads. Higher stocking levels lead to increased
competition for resources, reduced tree vigor, and increase the risk of insect
outbreak and disease.
Abstract: Stand conditions associated with outbreak populations of the
roundheaded pine beetle, Dendroctonus adjunctus Blandford, in ponderosa pine,
Pinus ponderosa Dougl. ex Laws., forests were studied in the Pinaleno
Mountains, AZ, and the Pine Valley Mountains, UT. Classification tree models to
estimate the probability of infestation based on stand attributes were built for
both study areas using growth rate and ponderosa pine basal area information.
Cross-validation estimates of correct classification were 0.60 for the Pinaleno
Mountains and 0.58 and 0.78 for the Pine Valley Mountains. Regression tree and
linear regression models to estimate amount of mortality caused by the beetles
were also built for both sites using growth rate, ponderosa pine basal area, and
trees per hectare information. The occurrence and mortality levels caused by the
roundheaded pine beetle are positively related at both the stand and tree scale
with reduced growth rates caused by high stocking densities.
Negrón, J.F., Wilson, J.L., Anhold, J.A. 2000. Stand conditions associated
with roundheaded pine beetle (Coleoptera: Scolytidae) infestations in
Arizona and Utah. Environmental Entomology 29: 20-27.
This study used stand and tree characteristics in the Pine Valley and Pinaleno
Mountains. preferred by the roundheaded pine beetle to develop probability of
infestation and extent of mortality models for management use. High stand
densities and reduced growth rates in preceding years result in an increased risk
of roundheaded pine beetle infestation. These conditions may negatively impact
resin production and tree defenses. There is expected to be an increase in the
intensity of and area impacted by the roundheaded pine beetle as a result of
overstocking and fire suppression in southwestern forests.
Abstract: Insect-caused tree mortality, fires, and pathogens are primary
disturbance agents in forest ecosystems. The mountain pine beetle,
Dendroctonus ponderosae Hopkins, is a bark beetle that can cause extensive
mortality in ponderosa pine, Pinus ponderosa Lawson, along the Colorado Front
Range. Despite the history of outbreaks of this insect in Colorado, no models
have been developed to estimate the probability of infestation. Thirty-five clusters
of one infested and three baseline plots were established from 1998 to 2000 in
the Arapaho-Roosevelt National Forest in north-central Colorado to develop
empirical models of probability of infestation based on forest conditions.
Mountain pine beetle-infested plots exhibited higher basal area and stand density
index (SDI) for ponderosa pine and for all tree species combined, and higher
number of ponderosa pine trees per hectare. Within infested plots, infested trees
were larger in diameter at breast height and in the dominant and co-dominant
crown positions. A classification tree model indicated that the likelihood of
infestation by mountain pine beetle is 0.71 when ponderosa pine basal area is
>17.1 m2/ha at the stand level. A second plot-level model indicated that the
probability of infestation increased with increasing ponderosa pine SDI,
ponderosa pine quadratic mean diameter, and total basal area. For individual
trees within infested plots the likelihood of infestation was 0.77 for dominant or
co-dominant trees >18.2 cm in diameter at breast height. Results are consistent
with other studies that have documented increased likelihood of infestation or
enhanced mortality levels or both as a result of higher host type stocking. The
simple models developed should help to guide silvicultural treatments and
restoration efforts by establishing stocking levels below which mountain pine
beetle-caused mortality is less likely, particularly in the dry sites and poor
growing conditions characteristic of the Colorado Front Range.
Neilson, R.P. 1995. A model for predicting continental scale vegetation
distribution and water balance. Ecological Applications 5: 362-385.
This paper describes the Mapped Atmosphere-Plant-Soil System (MAPSS)
which is a biogeographical model developed to use mechanistic calculations of
water balance and competition between plant types for resources to predict
vegetation distribution, soil moisture, and runoff patterns in alternative climates.
MAPSS makes extensive use of a leaf area index as a basis for model
predictions.
Nowak, R.S., Ellsworth, D.S., Smith, S.D. 2004. Functional responses of
plants to elevated atmospheric CO2 – do photosynthetic and productivity
data from FACE experiments support early predictions? New Phytologist
162: 253-280.
This paper seeks to determine the validity of early predictions of the impacts of
elevated CO2 on plant and ecosystem processes. Measurements taken at Mauna
Loa indicate a 32% increase in CO2 over the past 250 years. Increases are
projected to be from 93%-246% by the year 2100. Decreased stomatal
conductance and reduced small root biomass may allow plants in water limited
environments to maintain growth and productivity.
Paine, T.D. 1984. Seasonal response of ponderosa pine to inoculation of
the mycangial fungi from the western pine beetle, Canadian Journal of
Botany 62(3): 551-555.
This paper studied the response of host conifers to fungal infection and the
change in response throughout the year and to determine if fungal growth was
reduced by compounds deposited in the hypersensitive lesions. During
colonization of ponderosa pine, female western pine beetles inoculate host trees
with two species of fungi. These fungi are located in the mycangium, a cuticular
pocket on the anterior of the prothorax.
Paine, T.D., Stephen, F.M. 1987a. Influence of tree stress and site quality
on the induced defense system of loblolly pine. Canadian Journal of Forest
Research 17: 569–571.
This was a study to determine if the size of the hypersensitive lesion in loblolly
pine which confines fungal growth is related to site conditions and tree growth
characteristics. Low oleoresin pressure may impact flow of terpenes and xylem
resin and reduce constitutive defenses during infection, wounding, or bark beetle
colonization. The increased level of hypersensitive response in June may be the
result of site differences or longer periods of daylight and higher temperatures.
Paine, T.D., Stephen, F.M. 1987b. The relationship of tree height and crown
class to the induced plant defenses of loblolly pine. Canadian Journal of
Botany 65: 2090–2092.
This study determined if the diameter class of the tree influenced the size of the
response and examined the relative size of the response at the initial colonization
height. Differences in site conditions were correlated with the intensity of
response to wounding or inoculation. The two larger diameter classes on the
well-drained upland site produced heavier responses than in the slower growing
trees on the bottomland plot.
Parmesan, C., Yohe, G. 2003. A globally coherent fingerprint of climate
change impacts across natural systems. Nature 421: 37-42.
This paper presents a model that considers three variables: proportion of
observations matching climate change predictions, competing explanations for
these observations, and the confidence in attributing each of these observations
to climate change. While some temperate species have undergone range
expansion and increased their abundance, many polar species have decreased
their range and abundance. The meta-analysis of 334 species determined that
84% showed predicted sign switches, a diagnostic indicator of climate change.
Pimmentel, D., Wilson, C., McCullum, C., Huang, R., Dwen, P., Flack, J.,
Tran, Q., Saltman, T., Cliff, B. 1997. Economic and environmental benefits
of biodiversity. Bioscience 47: 747-757.
This study assesses the economic and environmental benefits of organic waste
disposal, biological nitrogen fixation, biological pest control, pollination and
pharmaceuticals. Biological treatments could convert approximately 75% of
environmental pollutants into less toxic materials using plants and microbes.
Costs for remediation of chemical pollution worldwide would decrease by almost
90% if bioremediation was implemented. Plant breeding for resistance genes has
significantly reduced the use of insecticides and improved crop yields.
Pope, V.D., M.L. Gallani, P.R. Rowntree, R.A. Stratton. 2000. The impact of
new physical parameterizations in the Hadley Centre climate model:
HadAM3. Climate Dynamics 16:123-146.
The purpose of this study was to make changes to the physical paprameters of
the HadAM2b and assess the impacts of those changes on reducing systematic
errors. The HadAM3 Global Circulation Model from UKMO has been improved in
several areas compared to its predecessor HadAM2b. HadAM3 uses a new
radiation scheme, convective momentum transport, a new land surface scheme
(MOSES), and includes the new capabilities of including radiative effects of
aerosols and trace gases, and the effects of CO2 on evaporation at the land
surface.
Powell, J. and B. Bentz. Connecting phenological predictions with
population growth rates for mountain pine beetle, an outbreak insect.
Journal of Difference Equations and Applications, Cushing Special Issue,
submitted March 2008.
This paper combines a mathematical framework describing Mountain pine beetle
success at the landscape level with a phonological distribution model in an effort
to connect tree level phenology predictions and population growth rates. Timing
of life stages and synchrony of emergence are highly evolved and specialized for
different species. The rise in temperature and altered degree of developmental
synchrony associated with climate change has been implicated in recent
mountain pine beetle outbreaks.
Powell, J.A., Logan, J.A. 2005. Insect Seasonality -- Circle Map Analysis of
Temperature-Driven Life Cycles. Theoretical Population Biology 67: 161179.
This paper describes a mathematical model relating temperature to bark beetle
voltinism, and incorporating several developmental rates for different life stages,
can be represented in non-linear circle maps. The model predicts synchrony of
beetle emergence, despite differing dates of oviposition, through incorporating
pauses in development from quiescence or other temperature thresholds to
development. Slight variances in temperature bands can quickly prevent
univoltinism.
Abstract: Maintaining an adaptive seasonality, with life cycle events occurring at
appropriate times of year and in synchrony with cohorts and ephemeral
resources, is a basic ecological requisite for many cold-blooded organisms.
There are many mechanisms for synchronizing developmental milestones, such
as egg laying (oviposition), egg hatching, cocoon opening, and the emergence of
adults. These are often irreversible, specific to particular life stages, and include
diapause, an altered physiological state which can be reversed by some
synchronizing environmental cue (e.g. photoperiod). However, many successful
organisms display none of these mechanisms for maintaining adaptive
seasonality. In this paper we briefly review the mathematical relationship
between environmental temperatures and developmental timing and discuss the
consequences of viewing these models as circle maps from the cycle of yearly
oviposition dates and temperatures to oviposition dates for subsequent
generations. Of particular interest biologically are life cycles which are timed to
complete in exactly one year, or univoltine cycles. Univoltinism, associated with
reproductive success for many temperate species, is related to stable fixed
points of the developmental circle map. Univoltine fixed points are stable and
robust in broad temperature bands, but lose stability suddenly to maladaptive
cycles at the edges of these bands. Adaptive seasonality may therefore break
down with little warning with constantly increasing or decreasing temperature
change, as in scenarios for global warming. These ideas are illustrated and
explored in the context of Mountain Pine Beetle (Dendroctonus ponderosae
Hopkins) occurring in the marginal thermal habitat of central Idaho’s Rocky
Mountains. Applications of these techniques have not been widely explored by
the applied math community, but are likely to provide great insight into the
response of biological systems to climate change.
Powell, J. A., J. Jenkins, J. Logan and B. Bentz. 2000. Seasonal
temperature alone can synchronize life cycles. Bulletin of Mathematical
Biology 62: 977-998.
This study modeled the development of the mountain pine beetle (Dendroctonus
ponderosae Hopkins) to determine if seasonal temperature swings in the
absence of diapause can result in adaptive seasonality.The rate of development
varies with temperature and life-stages and ceases at stage specific thresholds.
Voltine boundaries are discontinuous when temperatures fall through
developmental thresholds causing development to stop for those below the
threshold.
Abstract: In this paper we discuss the effects of yearly temperature variation on
the development and seasonal occurrence of poikiliothermic organisms with
multiple life stages. The study of voltinism in the mountain pine beetle
(Dendroctonus ponderosae Hopkins), an important forest insect living in extreme
temperature environments and exhibiting no diapause, provides a motivational
example. Using a minimal model for the rates of aging it is shown that seasonal
temperature variation and minimal stage-specific differences in rates of aging are
sufficient to create stable uni- and multi-voltine oviposition cycles. In fact, these
cycles are attracting and therefore provide an exogenous mechanism for
synchronizing whole populations of organisms. Structural stability arguments are
used to extend the results to more general life systems.
Progar, R.A. 2005. Five-year operational trial of verbenone to deter
mountain pine beetle (Dendroctonus ponderosae; Coleoptera: Scolytidae)
attack of lodgepole pine (Pinus contorta). Environmental Entomology 34:
1402–1407.
This study assessed the ability of verbenone to deter mass attack by mountain
pine beetle on varied dbh size class trees over the course of an outbreak.
Verbenone alone was only partially effective in protecting stands from intiial
attack by mountain pine beetles. Effectiveness may have been influenced by
naturally produced verbenone decreasing the gradient between treated and
untreated plots and habituation from remaining in treated areas for extended
periods.
Abstract: The antiaggregation pheromone verbenone was operationally tested
for 5 yr to deter mass attack by the mountain pine beetle on lodgepole pine in
campgrounds and administrative areas surrounding Redfish and Little Redfish
Lakes at the Sawtooth National Recreation Area in central Idaho. Each year, fivegram verbenone pouches were evenly distributed (-10 m apart) within seven of
14 0.2-ha plots. During the first 2 yrs. of the study a median of 12% of the host
trees >13 cm dbh were attacked and killed on the treated plots, whereas trees on
the untreated plots incurred a median mortality of 59%. When ~50% of the trees
on the untreated plots were killed a detectable beetle response to verbenone on
the treated plots dramatically declined. After 5 yr, mountain pine beetle had killed
a median of 87% of the lodgepole pine trees >13 cm in untreated plots and 67%
in plots containing verbenone pouches. Beetle pressure was higher on untreated
plots in 2000 and 2001, nearly equal between treatments in 2002, higher on
verbenone-treated plots in 2003, and similar between treatments in 2004. It is
hypothesized that the lack of response to verbenone after 2 yr may be related to
both population size and spatial scale, i.e., large numbers of vigorous beetles in
a local area with a reduced number of preferred large-diameter trees become
crowded and stressed, causing a decline in the response to verbenone. The 2-yr
delay in widespread pine mortality caused by verbenone would have given land
managers time to use other management tactics to deter catastrophic loss of
trees caused by mountain pine beetle.
Pureswaran, D.S., Borden, J.H. 2005. Primary attraction and kairomonal
host discrimination in three species of Dendroctonus (Coleoptera:
Scolytidae). Agricultural and Forest Entomology 7: 219–230.
This study tested the ability of three species of Dendroctonus to discriminate
between host and non-host volatiles in combination with attractant pheromones
and whether primary attraction occurred in response to bole and floilage volatiles
of host conifers. D. ponderosae showed no preference to host or non host or
between live and dead hosts indicating no primary attraction for this species.
Production of aggregation pheromones by pioneer beetles results in a secondary
attraction necessary for overwhelming host defenses during mass attack.
Raffa, K.F., Aukema, B.H., Erbilgin, N., Klepzig, K.D., Wallin, K.F. 2005.
Interactions among conifer terpenoids and bark beetles across multiple
levels of scale: An attempt to understand links between populations
patterns and physiological processes. Recent Advances in
Phytochemistry 39: 79-118.
This chapter discusses the interaction between bark beetles and their fungal
assoaciates and various constitutive and inducible host terpene defenses.
Functioning in an integrated system, constitutive and induced monoterpene
defenses in red pine produced a high enough concentration to kill 90% of
attacking Ips pini after 3 days. Aggregation pheromones are produced from
oxygenated terpenes by de novo synthesis or from host compounds.
Raffa, K.F., Phillips, T.W., Salom, S.M. 1993. Strategies and mechanisms of
host colonization by bark beetles. Pgs. 103–128, In: Schowalter, T.D., Filip,
G.M. (eds.), Beetle Pathogen Interactions in Conifer Forests, Academic
Press, London.
This chapter focuses on the chemical and histological barriers to bark beetle
colonization of the subcortical environment and strategies used by bark beetles
to overcome host defenses. All species of Scolytids use aggregation
pheromones for host and mate finding. Aggressive species produce pheromones
that attract conspecifics, a requirement for the mass attack stategy used to
overwhelm host defenses.
Raffa, K.F, B. H. Aukema, B. J. Bentz, A. L. Carroll, J. A. Hicke, M. G. Turner,
W. H. Romme. 2008. Cross-scale Drivers of Natural Disturbances Prone to
Anthropogenic Amplification: Dynamics of Biome-wide Bark Beetle
Eruptions. BioScience 58(6):501-518.
This study focuses on the factors that trigger bark beetle outbreaks and how
climate change and greenhouse gases impact the frequency, severity, and
synchrony of outbreaks. Life history, timing of stand disturbances, species, and
successional role determine how forests respond to bark beetle populations.
Habitat fragmentation and forest homogeneity can greatly influence bark beetle
outbreak dynamics. Management practices combined with the effects of global
warming such as increased temperature and altered precipitation patterns
increase the risk of outbreak.
Reeve, J.D., Ayres, M.P., Lorio, Jr., P. 1995. Host suitability, predation, and
bark beetle population dynamics. Pg 339-357 In: Cappuccino, N., Price, P.
eds. Population dynamics: new approaches and synthesis. Academic
Press, Inc., San Diego, CA.
This chapter assesses the impact of moderate and severe water stress on host
suitability and colonization as well as southern pine beetle-predator interactions.
Water availability impacts host suitability is a major factor in assessing the risk of
southern pine beetle outbreak. Future patterns of high midsummer precipitation
may extend the earlywood growth period favoring southern pine beetle
population growth. Moderate water deficits reduce growth but maintain
photosynthesis allowing for increased secondary metabolism and oleoresin
production.
Rehfeldt, G.E., Crookston, N.L., Warwell, M.V., Evans, J.S. 2006. Empirical
analyses of plant-climate relationships for the western United States.
International Journal of Plant Science 167: 1123–1150.
This study used presence-absence data, statistical moels, and a fine spatial
scale to develop models for predicting plant communities and their constituent
species. The Random Forests algorithm predicts the spatial shifting of
community profiles with only 55% showing the same profiles after one century.
Increasing temperatures and changes in precipitation patterns are predicted to
drastically reduce the area occupied by L. occidentalis, P. edulis, P. englemannii,
and J. osteosperma.
Abstract: The Random Forests multiple-regression tree was used to model
climate profiles of 25 biotic communities of the western United States and nine of
their constituent species. Analyses of the communities were based on a gridded
sample of ca. 140,000 points, while those for the species used presenceabsence data from ca. 120,000 locations. Independent variables included 35
simple expressions of temperature and precipitation and their interactions.
Classification errors for community models averaged 19%, but the errors were
reduced by half when adjusted for misalignment between geographic data sets.
Errors of omission for species-specific models approached 0, while errors of
commission were less than 9%. Mapped climate profiles of the species were in
solid agreement with range maps. Climate variables of most importance for
segregating the communities were those that generally differentiate maritime,
continental, and monsoonal climates, while those of importance for predicting the
occurrence of species varied among species but consistently implicated the
periodicity of precipitation and temperature-precipitation interactions. Projections
showed that unmitigated global warming should increase the abundance
primarily of the montane forest and grassland community profiles at the expense
largely of those of the subalpine, alpine, and tundra communities but also that of
the arid woodlands. However, the climate of 47% of the future landscape may be
extramural to contemporary community profiles. Effects projected on the spatial
distribution of species-specific profiles were varied, but shifts in space and
altitude would be extensive. Species-specific projections were not necessarily
consistent with those of their communities.
Rehfedlt, G.E., Tchebakova, J.M., Milyiutin, L.I., Parfenova, Y.I., Wykoff,
W.R., Kouzmina, N.A. 2003. Assessing population responses to climate in
Pinus sylvestris and Larix spp. of Eurasia with climate-transfer models.
Eurasian Journal of Forest Research 6-2:83-98.
The purpose of this study was to develop and interpret climate-transfer functions
and to use them to define climatypes. Under the Hadley greenhouse gas
scenario scots pine would experience a short term reduction in growth and
productivity in central and southern portions of Eastern Europe and in southern
Asia. Evolutionary impacts include gains in growth and productivity in Siberia and
northeastern Europe and shifts in distribution in Eastern Europe.
Abstract: Weibull regression models were used to relate height and survival of
Eurasion populations of Scots pine (Pinus sylvestris L.) at age 13 and three
species of larch (L. sukaczewii Dylis, L. sibirica Ledeb., and L. gmelinii (Rupr.)
Rupr.) at age 12 to the difference in climate between their provenance and a
planting site. Univariate models using five climate variables as predictors all were
statistically significant (p < 0.01), and all but the pine survival functions received
strong verification with independent data. The models showed that the growth
and survival of most populations of the pine and each pecies of larch are
enhanced when populations are transferred from their provenance to warmer
climates. The results are consistent with the view that most populations occur in
climates that are suboptimal, the degree of which is directly related to the
severity of the climate. Because of this projected responses to a climate-change
scenario o the Hadley Centre were highly variable geographically. Short-term
plastic responses tended to be strongly negative for the least severe climates
and strongly positive for the most sever. Long-term evolutionary responses
primarily reflected extirpation and immigration for the species of larch but showed
additionally for the pine that the accommodation of global warming will require a
redistribution of genotypes throughout the species’ range.
Rehfedlt, G.E., Tchebakova, J.M., Parfenova, Y.I., Wykoff, W.R., Kuzmina,
N.A., Milyiutin, L.I. 2002. Intraspecific response to climate change in Pinus
sylvestris. Global Change Biology 8: 912–929.
This paper assembled heterogenous data from disparate provenance tests and
adjusted trees heights to a common age to determine the response of Pinus
sylvestris to climate change. Model predictions show that future climates will be
best suited to species that are not present today.This study shows that climate
types of P. sylvestris best suited for the conditions projected for 2090 climate are
>1000km from their future optimum habitat. The rapid pace of global warming
combined with discrete generations of P. sylvestris lasting more than 100 years
create a lag in genetic response of 1500 years or longer.
Abstract: Five population-specific response functions were developed from
quadratic models for 110 populations of pinus sylvestris growing at 47 planting
sites in Eurasia and North America. The functions predict 13 year height from
climate degree-days >5°C; mean annual temperature; degree days <0°C;
summer-winter temperature differential; and a moisture index, the ratio of degree
days > 5°C to mean annual precipitation. Validation of the response functions
with two sets of independent data produced for all functions statistically
significant simple correlations with the coefficients as high as 0.81 between
actual and predicted heights. The response functions described the widely
different growth potentials typical of natural populations and demonstrated that
these growth potentials have different climatic optima, with the disparity between
the optimal and inhabited climates becoming greater as the climate becomes
more severe. When driven by a global warming scenario of the Hadley Center,
the functions described short-term physiologic and long-term evolutionary effects
that were geographically complex. The short-term effects should be negative in
the warmest climates but strongly positive in the coldest. Long-term effects
eventually should ameliorate the negative short-term impacts, enhance the
positive, and in time, substantially increase productivity throughout most of the
contemporary pine forests of Eurasia. Realizing the long-term gains will require
redistribution of genotypes across the landscape, a process that should take up
to 13 generations and therefore many years.
Regniere, J., Bentz, B. 2007. Modeling cold tolerance in the mountain pine
beetle, Dendroctonus ponderosae. Journal of Insect Physiology 53: 559572.
This paper developed a cold tolerance model using hourly phloem temperature
readings and measurements of the supercooling point (SCP) of individual larvae
at six field locations. The SCP is the temperature at which lethal ice crystals form
in body tissues. The SCP is often considered a measure of maximum cold
hardiness although there is substantial mortality at temperatures above the SCP.
Cold tolerance and cryoprotectant accumulation are major determinants of an
insects supercooling capacity.
Régnière, J., Sharov, A. 1999. Simulating temperature-dependent
ecological processes at the sub-continental scale: male gypsy moth flight
phenology as an example. International Journal of Biometeorology. 42(3):
146-152.
This study looked at the usefulness of both universal kriging and multiple
regression interpolation for mapping the flight of the male gypsy moth in North
America. It was found that, for kriging, results based from an equation
incorporating elevation as an external drift variable, and a more complex
equation incorporating an external drift variable as well as two trend terms,
performed virtually the same. Kriging cross validation results were slightly better
than those of multiple regression interpolation, however, kriging requires more
computing time.
Régnière J, St-Amant R. 2007. Stochastic simulation of daily air
temperature and precipitation from monthly normals in North America
north of Mexico. International Journal of Biometeorology 51: 415-430.
This paper identified and remedied weaknesses in the Régnière and Bolstad
algorithm and added daily precipitation to its output generating a realistic daily
times series of minimum and maximum air temperature and precipitation.
Applying a small amount of stochastic annual variation to monthly mean
minimum and maximum temperatures may help to achieve low frequency
interannual variability. General Circulation Model outputs currently do not reflect
precipitation patterns at regional scales.
Reynolds KM, Holsten EH. 1994. Relative importance of risk factors for
spruce beetle outbreaks. Canadian Journal of Forest Research 24: 20892095.
This study analyzes the relative importance of spruce beetle outbreak risk factors
such as stand susceptibility, spruce beetle population size and trend, cumulative
degree days from June of the previous year, and precipitation from the previous
summer. Spruce beetle population size and weather patterns are major
determinants of outbreak risk, and can vary considerately from year to year.
Temperature is an important factor in population dynamics as it relates to flight
period, life stages, and developmental rates. Higher than normal summer
temperatures can lead to an increase in univoltism in spruce beetle populations.
Abstract: Nine factors were initially suggested by spruce beetle (Dendroctonus
rufipennis (Kby.)) experts in Alaska as potentially important in determining the
risk of a spruce beetle outbreak in stands. Factors suggested were stand hazard,
size and trend of spruce beetle population in neighboring stands, degree-days in
the past June, total rainfall in the past summer, and availability hierarchy
process. This process derives subjective estimates of factor importance values
through a process of a pair-wise comparison. Analysis in stage 1 involved
independent responses of two experts from Alaska. In stage 2, three experts
from Alaska provided responses as a group. In stage 3, five experts,
representing Alaska, British Columbia, and the Rocky Mountain region, provided
responses as a group. N the final stage of analysis, stand hazard and
windthrown were considered about equally important factors determining risk of a
spruce beetle outbreak. Hazard and windthrown were considered about equally
important and together accounted for almost two-thirds of the total allocation of
importance values among risk factors. The analytic hierarchy process is an
effective method for eliciting expert knowledge and can be a useful tool for
development of expert systems in natural resource management, where even
expert knowledge is often incomplete.
Ring, R.A., 1977. Cold-hardiness of the bark beetle, Scolytus ratzeburgi
Jans. (Coleoptera : Scolytidae), Norwegian Journal of Entomology 24, 125136.
This study assessed cold adaptations in Scolytus ratzeburgi by testing for frost
resistance and supercooling potential at different temperatures for varying
periods of time and studying changes in blood sugars or sugar alcohols. S.
ratzeburgi larvae that acclimated for 12 weeks at -10°C had a 100% survival rate
but no larvae survived even brief exposure to -30°C. Larvae brought into the
laboratory from the field and maintained at 23°C lost all glycerol within 2-4 days
indicating that glycerol concentrations are regulated by temperature.
Roe, G.H. and Baker, M.B. 2007. Why is climate sensitivity so
unpredictable? Science 318(5150): 629-632.
This paper investigates the equilibrium change in global annual mean surface air
temperature resulting from a sustained doubling of atmospheric CO2 over
preindustrial levels. The sum of uncertainties from component feedback
processes can be interpreted as variability in strength of major feedbacks,
uncertainties in observations or in understanding physical processes.
Roff. D. 1980. Optimizing development time in a seasonal environment:
the “ups and downs” of clinal variation. Oecologia 45: 202-208.
This paper outlines a mathematical model that addresses various life-history
components and predicts the type of clinal variation observed. In bivoltine
populations of the band legged cricket, it is the second generation that adapts to
variations in season length. In regional bivoltine populations of the rice stem
borer, development time decreases with an increase in latitude.
Romme, W.H., Knight, D.H., Yavitt, J.B. 1986. Mountain pine beetle
outbreaks in the Rocky Mountains: Regulators of primary productivity?
American Naturalist 127: 484–494.
This study was designed to examine the effects of mountain pine beetle
outbreaks on primary productivity with resource distribution taking place over
decades. At the landscape level, fire may help to maintain a constant level of
productivity, with bark beetle outbreaks increasing the risk of fire in individual
stands. Studies done in the Yellowstone and Grand Teton national parks indicate
that bark beetle outbreaks increased variation in forest production.
Rouault, G., Candau, J-N., Lieutier, F., Nageleisen, L-M., Martin, J-C.,
Warzée, N. 2006. Effects of drought and heat on forest insect populations
in relation to the 2003 drought in western Europe. Annals of Forest Science
63: 613-624.
This paper reported on the relationship between water stress and the decline in
host tree resistance to insect attack during the European drought and heat wave
of 2003. Under conditions of severe drought stress, many species of trees
experience a simultaneous reduction in constitutive resin flow and production of
secondary metabolites necessary for defense.
Rudinsky, J.A. 1962. Ecology of Scolytidae. Annual Review of
Entomology 7: 327–348.
This is a study of the family Scolytidae including groups, factors influencing larval
development, host selection, host defenses, and population dynamics. The bark
and wood of host trees provide an insulating buffer for beetles exposed to
temperature extremes with bark beetles developing under dark or thin bark being
at increased risk of mortality. Voltinism in many species is determined by the
extent and duration of favorable temperatures. Risk of outbreak increases in
areas with low water holding capacity, windthrow, shallow roots systems, or
prolonged drought.
Running, S.W. 2006. Is global warming causing more, larger wildfires?
Science 313: 927-928.
This paper discusses the role of climate change in increasing the length of the
fire season and the duration of fires. Over the past 50 years the western United
States has experienced a 1-4 week earlier melting of snowpacks combined with
average spring and summer temperature increases of ~0.9°C. This has resulted
in a 78 day increase in the length of the fire season, and a five-fold increase in
duration of large fires.
Ryan, R.B. 1959. Termination of diapause in the Douglas-fir beetle,
Dendroctonus pseudotsugae Hopkins (Coleoptera: Scolytidae), as an aid to
continuous laboratory rearing. The Canadian Entomologist 91: 520-525.
This study evaluated the effects of differing cold temperatures and various time
regimens on the termination of diapauses in the Douglas-fir beetle. Beetles
dissected during diapause showed underdeveloped flight muscles and gonads.
Endocrine activity responsible for flight muscle development and maturation of
the gonads is likely stimulated by adequate chilling during diapause.
Safranyik, L. and Carroll. 2006. The biology and epidemiology of the
mountain pine beetle in lodgepole pine forests, Natural Resources Canada,
Canadian Forest Service, Pacific Forestry Centre, Victoria, BC. pp 3-66,
Available electronically (free) at: http://bookstore.cfs.nrcan.gc.ca/
This chapter reviews the biology, habits, and population dynamics of the
mountain pine beetle (MPB) with emphasis on the interaction between MPB and
its associated fungi and its primary host lodgepole pine. Cold winter
temperatures are the primary cause for beetle mortality, and temperature dictates
development at every life stage as well as emergence and flight patterns.
Distribution is also determined by wind direction and speed; most beetles will not
fly at wind speed that exceed their own maximum wing speed, and also tend to
fly downwind upon emergence, flying upwind only after encountering attack
pheromones.
Safranyik, L., Linton, DA. 1988. Distribution of attacks on spruce stumps by
the spruce beetle, Dendroctonus rufipennis (Kirby) (Coleoptera:
Scolytidae), and effects on the length of egg galleries. The Canadian
Entomologist 120(1): 85-94.
This study describes the vertical density gradient of spruce beetle attacks on
spruce stumps and develops a model of attack density as a function of stump
height. Responses to heat, light, and suitability for brood survival in host choice
of D. rufipennis results in an increase in attack densities on shaded portions of
stumps and logs. Drying of inner bark on exposed portions of the stump reduces
suitability for attack.
Safranyik, L., Shrimpton, D.M., Whitney, H.S. 1975. An interpretation of the
interaction between lodgepole pine, the mountain pine beetle and its
associated blue stain fungi in western Canada. Pages 406-428 in D.M.
Baumgartner, ed. Management of lodgepole pine ecosystems. Washington
State University Cooperative Extension Service, Pullman, WA.
This paper developed a climate suitability and outbreak risk index for the
mountain pine beetle using four principal variables and two modifying variables.
The principle variables were 1) more than 550 degree-days heat accumulation
above 42°F from August 1 through the end of the effective growing season, and
more than 1,500 degree-days heat accumulation within the growing season from
August 1 to July 31 of the following year; 2) minimum winter temperatures higher
than -40°F; 3) average maximum August temperature higher than 65°F; 4) total
precipitation during April, May and June less than the long-term averages for
these months. Modifying variables were 5) the variability of growing season
precipitation (coefficient of variation), and 6) the average annual water deficit.
Sahota, T.S., Thompson, A.J. 1979. Temperature induced variation in the
rates of reproductive processes in Dendroctonus rufipennis (Coleoptera:
Scolytidae): A new approach to detecting changes in population quality.
The Canadian Entomologist 111: 1069-1078.
This study measured reproductive processes such as rate of obtaining nutrients,
nutrient conversion rates, yolk deposition, the rate of obtaining oviposition sites,
and the duration of the reproductive period as a measure of population quality.
Gonadotrophic function of the corpora allata may be temperature dependent.
Lower temperatures during gallery construction resulted in longer, egg-free
galleries.
Salinas-Moreno Y., Mendoza M.G., Barrios M.A., Cisneros R., MacíasSámano J., Zúñiga G. 2004. Areography of the genus Dendroctonus
(Coleoptera: Curculionidae: Scolytinae) in Mexico. Journal of
Biogeography 31: 1163-1177.
This atlas details the distribution, altitudinal range, and variety of hosts
associated with each species of Dendroctonus. As a result of extensive logging
over the past hundred years, the structure and composition of plant communities
has been altered. Most present day forests are second-growth forests in which
the dominant species is not the original species. These forests may be at greater
risk for bark beetle outbreaks which, when combined with fire and human activity,
are the major causes of forest degradation in Mexico.
Salinas-Moreno, Y., Carlos F. Vargas Mendoza, C.F., Zúñiga, G., Víctor, J.,
Ager, A., Hayes, J.L. Atlas de distribución de descortezadores del género
Dendroctonus (Curculionidae: Scolytinae) y zonas históricas de mayor
presión en los bosques de pino de México. Comisión Nacional Forestal y
Instituto Politécnico Nacional. In press.
This study analyzed the geographical distribution of each species, spatial
variation in species richness, overlapping of species ranges, and disjunction
patterns of 12 Dendroctonus species which infest twenty-five of the 42 pine
species found in Mexico. Beetle distribution is closely linked with the distribution
of host trees. Of the twelve Dendroctonus species that are found in Mexico, only
D. mexicanus, D. frontalis, D. rhizophagus, and D. adjunctus cause substantial
infestations.
Abstract: Objective was to analyse whether the geographical ranges of
Dendroctonus species are (1) associated with factors such as host species or
elevation, and (2) in agreement with Halffter’s Nearctic distribution pattern. (3) To
identify and discuss the factors that are likely to act as barriers to the genus’
geographical distribution. (4) To explore whether there is an association between
the size of the geographical ranges of Dendroctonus species and the number of
Pinus host species used by each of them, and (5) to assess if these host species
are most common at the elevations preferred by the individual Dendroctonus
species.
Saxe, H., Ellsworth, D.S., Heath, J. 1998. Tree and forest functioning in an
enriched CO2 atmosphere. New Phytologist 139: 395-436
This paper examines the recent literature on long-term and large-scale studies of
elevated CO2 with emphasis on tree and forest responses and functioning.
Studies in fields relating to tree and forest functions in increased CO 2
environments are limited through their methods of data gathering, and are often
unable to account for different reactions to elevated CO2 within a single tree, let
alone within an entire ecosystem. Matters are further complicated by littleunderstood feedback loops and the lack of modeling systems that can accurately
predict on a small or local scale.
Schaupp, W.C., Johnson, F.M. 1999. Evaluation of the spruce beetle in
1998 within the Routt Divide blowdown of October 1997, on the Hahns Peak
and Bears Ears Ranger Districts, Routt National Forest, Colorado. USDA
Forest Service Biological Evaluation R2-99-08.
This study used aerial survey maps, pheromone trapping, extrent surveys, and
brood sampling to determine the extent of a spruce beetle infestation in wind
thrown trees which occurred after a major blowdown event in Routt National
Forest, an area without a history of beetle infestation. Several broods examined
in wind thrown trees were found to have an atypical 1-year life cycle. The beetle
infestation was predicted to continue for several years in the downed trees before
advancing to surrounding forest to kill live spruce trees at un-manageable levels.
Schär, C., Jendritzky, G. 2003. Hot news from summer 2003. Nature 432:
559-560.
This paper discusses anthropogenic contribution to climate change as an
explanation for warmer temperatures and a recent heatwave in Europe. The two
week peak of the European 2003 summer heat wave caused an estimated (US)
12.3 billion dollar loss in crops, (US)1.6 billion dollars of fire damage, damages
from rockslide (as a result of glacier melt), and unusually high human mortality
rates. The probability of extreme heat waves increases in response to a warming
climate, and future events may become more frequent.
Schwartz, M.D., Ahas, R., Aasa, A. 2006. Onset of spring starting earlier
across the northern hemisphere. Global Change Biology 12: 343-351.
This study monitored the phenological change in plants in various regions of the
world in relation to warming trends showing that plants are responding to climate
change, though not at universal rates. Measures include indicators of phonology
such as appearance of first leaf bud growth, and temperature trends such as
warmer winters, earlier springs, and fewer frost days. In some regions, rate of
phonological change matches rate of climate change, while in others, it lags
behind or exceeds rate of climate change.
Scott, B.A. and A.A. Berryman. 1972. Larval diapause in Scolytus ventralis.
J. Entomol. Soc. Brit. Columbia 69:50-53.
This paper studied the effects of cold temperature on development and voltinism
in the fir engraver Scolytus ventralis. Significant portions of Scolytus ventralis
populations ordinarily enter diapause as larvae. 50-70% of larvae have
facultative diapauses initiated by undetermined stimuli (possibly 150-200 days of
cold exposure), while 30-50% enter obligatory diapause.
Scriber, J.M., Slansky, Jr., F. 1981. The nutritional ecology of immature
insects. Annual Review of Entomology 26: 183-211.
This review assesses importance of food quality relative to other environmental
factors and organism adaptations that influence post-digestion food utilization
and growth performance of immature arthropods. Food consumed, digested,
assimilated, excreted, metabolized and converted into biomass by insects in part
depends on the nutritional physiology of the host plant. Rapid decline of nitrogen
in trees and decreased leaf water contribute to low feeding performance of treefeeding insects. Physical wounding or stress from drought can alter plant
allelochemical composition, thus affecting larval feeding performance.
Seager, R., Ting, M., Held, I., Kushnir, Y., Lu, J., Vecchi, G., Huang, H-P.,
Harnik, N., Leetmaa, A., Lau, N-C., Li, C., Velez, J., Naik, N. 2007. Model
projections of an imminent transition to a more arid climate in
southwestern North America. Science 316: 1181-1184.
This study assessed several climate models that predict increasing aridity in the
southwest U.S. and northern Mexico. Relatively dry sub-tropic regions are
expected to get drier, while wetter high-latitude regions will become still wetter.
Future drought events such as La Nina will be even drier, as the base state will
be drier than any experienced since Medieval times.
Shaw, J.D., Steed, B.E., DeBlander, L.T. 2005. Forest inventory and
analysis (FIA) annual inventory answers the question: what is happening to
pinyon-juniper woodlands? Journal of Forestry 103:280–285.
This paper discusses the extent and severity of mortality in pinyon-juniper forests
of the southwest during the current drought as well as contributing mortality
agents. The drought in the southwestern US began around 1998, leading to
widespread pinyon pine mortality in the early 2000s, in part attributed to Ips
beetles. Ips beetles are, under normal circumstances, only moderately
aggressive, attacking and killing threes already under stress from another agent.
Periods of drought can result in outbreak populations.
Abstract: Widespread mortality in the pinyon-juniper forest type is associated
with several years of drought in the southwestern United States. A complex of
drought, insects, and disease is responsible for pinyon mortality rates
approaching 100% in some areas, while other areas have experienced little or no
mortality. Implementation of the Forest Inventory and Analysis (FIA) annual
inventory in several states coincided with the onset of elevated mortality rates.
Adjunct inventories provided supplemental data on damaging agents. Preliminary
analysis reveals the status and trends of mortality in pinyon-juniper woodlands.
Shaw, M.R., Loik, M.E., Harte, J. 2000. Gas exchange and water relations
of two Rocky Mountain shrub species exposed to a climate change
manipulation. Plant Ecology 146:197–206.
This paper studied two shrub species Artemisia tridentate and Pentaphylloides
floribunda to determine if rates of photosynthesis and/or transpiration are
enhanced and if plant water status changes under heating manipulation and if
these changes are correlated withseasonal changes in soil microclimate
conditions. Water use efficiency (WUE) in two shrub species at normal and
predicted future temperatures was measured by dividing instantaneous values of
net photosynthesis rater per unit leaf area by transpiration per unit leaf area. In a
warming climate, WUE is expected to decrease; however, this decrease could be
enhanced or modified by the associated increase in atmospheric CO2
concentration.
Shore, TL, Safranyik, L. 1992. Susceptibility and risk rating systems for the
mountain pine beetle in lodgepole pine stands. Forestry Canada, Inform.
Rep. BC-X-336
This study developed a susceptibility and risk rating system for the mountain pine
beetle which assesses not only stand susceptibility (through factors such as age,
dominant species, diameter of trees, location, and density), but also beetle
pressure, a factor previously excluded from risk rating systems. Thus, the risk
rating system is a function of both stand susceptibility indices, as well as beetle
pressure, forming a more comprehensive model of actual risk.
Shore, T.L., Safranyik, L., Lemieux, J.P. 2000. Susceptibility of lodgepole
pine stands to the mountain pine beetle: testing of a rating system.
Canadian Journal of Forest Research
This paper examined the susceptibility rating model devolved by Shore and
Safranyik in 1992 and found the system reliable for rating stand susceptibility to
bark beetle attack, it also includes an index for potential loss. The rating system
incorporates features from older models, but uses a continuous variable hazard
rating system, as opposed to two- or three-class rating systems. Variables
include tree age, diameter, climate, inter-tree competition (stand density), and
species composition of the stand.
Shugart, H.H. 2003. A Theory of Forest Dynamics: The Ecological
Implications of Forest Succession Models - Reprint of First Edition,
Copyright 1984. Springer-Verlag New York, Inc.
This book inspects and evaluates mathematical models of forest succession
applied to a range of scales and time periods and includes a review of ecological
succession and coverage of forest dynamics models. There may be changes in
community composition as a result of an unequal and species dependent
response to increased atmospheric CO2 concentration. The increase in
atmospheric CO2 concentration over the past 45 years has been primarily
attributed to the consumption of fossil fuels.
Sibold, J.S., T.T. Veblen, K. Chipko, L. Lawson, E. Mathis, and J. Scott.
2007. Influences of secondary disturbances on lodgepole pine stand
development in rocky mountain national park. Ecological Applications 17:
1638-1655.
This study looked at the relationship between secondary disturbances (surface
fire, mountain pine beetle, and wind thrown trees) and stand dynamics in postfire lodgepole pine forests. There is a relationship between mountain pine beetle
disturbances and stand dynamics, with severity and time between the original fire
disturbance and the secondary disturbance (age of the stand) both influencing
those dynamics, the latter having a stronger influence.
Abstract: Although high-severity fire is the primary type of disturbance shaping
the structure of lodgepole pine (Pinus contorta) stands in the southern Rocky
Mountains, many post-fire stands are also affected by blowdown, low-severity
surface fires, and/or outbreaks of mountain pine beetle (MPB; Dendroctonus
ponderosae). The ecological effects of these secondary disturbances are poorly
understood but are potentially important in the context of managing for ecological
restoration and fire hazard mitigation. We investigated the effects of blowdown,
surface fires, and MPB outbreaks on demographic processes in post-fire
lodgepole pine stands in Rocky Mountain National Park, Colorado, USA. We
used dendroecological methods to reconstruct stand characteristics prior to and
following secondary disturbances for paired stands with and without secondary
disturbances. Surface fire events do not kill canopy trees or trigger pulses of
recruitment and as such do not have detectable influences on stand
development. In contrast, both MPB and blowdown kill canopy trees and trigger
pulses of tree regeneration of lodgepole pine and subalpine fir (Abies lasiocarpa).
The amount and species composition of post-disturbance regeneration is
dependent on the severity of the disturbance and on the time since stand
initiation. Secondary disturbances of higher severity (i.e., killing .50% of the
canopy trees) that occur in younger post-fire stands favor new establishment of
lodgepole pine. In contrast, secondary disturbances of lower severity in older
stands (.250 years) trigger a pulse of establishment of subalpine fir. The results
of this study demonstrate that the high tree densities characteristic of lodgepole
pine stands in the southern Rockies (southern Wyoming to northern New Mexico)
are the result of dense regeneration following stand-replacing fires and that
surface fires had little or no thinning effect on tree densities. Thus, current high
stand densities in the study area are not the result of suppression of surface
fires. Moreover, the strong pulses of regeneration following forest thinning by
MPB and blowdowns imply that, depending on the degree of thinning, thinning
prescriptions to reduce fuels in the lodgepole pine forest type may have the
unintended consequence of increasing ladder fuels 15–20 years following
treatments.
Six, DL. 2003. A comparison of mycangial and phoretic fungi of individual
mountain pine beetles. Canadian Journal of Forest Research 33(7): 1331–
1334.
This study determined the fungi that are carried on the exoskeleton of
Dendroctonus ponderosae and compared them to the fungi carried in the
mycangia. Many bark beetles including the mountain pine beetle D. ponderosae,
have mycangia in which are transported associated fungi, although fungi can
also be transported phoretically on the exoskeleton. Of the two ophiostomatoid
fungi associated with the mountain pine beetle, O. clavigerum is primarily
transported in the mycangia, and is symbiotically beneficial to the beetle, while O.
montium is transported in both the mycangia and on the exoskeleton, and can be
harmuful to beetle brood production and development.
Abstract: Two ophiostomatoid fungi, Ophiostoma clavigerum (Robinson-Jeffrey
& Davidson) Harrington and Ophiostoma montium (Rumbold) von Arx, are known
to be associated with the mycangia of the mountain pine beetle, Dendroctonus
ponderosae Hopkins. However, virtually nothing is known regarding the phoretic
fungi carried on the external surface of the exoskeleton of this beetle. In this
study, I compared the phoretic fungi of individual D. ponderosae with the fungi
carried in their mycangia. As many beetles carried ophiostomatoid fungi on the
exoskeleton as in the mycangia; however, the species of ophiostomatoid fungus
carried phoretically on an individual beetle was not always the same as was
carried in its mycangia. Ophiostoma montium was isolated more often from
exoskeletal surfaces than from mycangia, while the reverse was true for O.
clavigerum. It appears that O. clavigerum is highly adapted for mycangial
dissemination, while O. montium is adapted to phoretic as well as mycangial
dissemination. Ophiostoma ips (Rumbold) Nannf. was phoretic on two beetles,
indicating that cross-contamination with fungi from cohabiting Ips spp. may
sometimes occur. Several non-ophiostomatoid fungi were isolated from
exoskeletal surfaces, but none consistently so. All non-ophiostomatoid fungi
isolated were common saprophytes often found in beetle killed trees. Yeasts
were also common and were isolated more often from the exoskeleton than from
mycangia.
Six, D.L., Bentz, B.J. 2003. Fungi associated with the North American
spruce beetle, Dendroctonus rufipennis. Canadian Journal of Forest
Research 33(9): 1815–1820.
This study examined Dendroctonus rufipennis sampled from six North American
study sites to determine fungal and yeast associates. D. rufipennis appears to
be associated with one predominant fungal species, Leptographium abietinum, a
pathogenically weak species whose possible role of aiding or hindering D.
rufipennis is unknown. Ceratocystic rufipenni was not found to be associated
with any of the samples in this study.
Abstract: Fungi were isolated from individual Dendroctonus rufipennis (Kirby)
collected from six populations in Alaska, Colorado, Utah, and Minnesota, U.S.A.
In all populations, Leptographium abietinum (Peck) Wingfield was the most
commonly isolated mycelial fungus (91–100% of beetles). All beetles in all
populations were associated with yeasts and some with only yeasts (0–5%). In
one population, Ophiostoma ips (Rumbold) Nannf. was also present on 5% of the
beetles but always in combination with L. abietinum and yeasts. Ophiostoma
piceae (Munch) H. & P. Sydow was found on 2% of beetles in another
population. Ceratocystis rufipenni Wingfield, Harrington & Solheim, previously
reported as an associate of D. rufipennis, was not isolated from beetles in this
study. Ceratocystis rufipenni is a virulent pathogen of host Picea, which has led
to speculation that C. rufipenni aids the beetle in overcoming tree defenses
and therefore contributes positively to the overall success of the beetle during
colonization. However, our results, considered along with those of others,
indicate that C. rufipenni may be absent from many populations of D. rufipennis
and may be relatively rare in those populations in which it is found. If this is true,
C. rufipenni may be only a minor or incidental associate of D. rufipennis and, as
such, not likely to have significant impacts on beetle success or population
dynamics. Alternatively, the rarity of C. rufipenni in our and others isolations may
be due to difficulties in isolating this fungus in the presence of other faster
growing fungi such as L. abietinum.
Six, D.L., Bentz, B.J. 2007. Temperature determines symbiont abundance
in a multipartite bark beetle-fungus ectosymbiosis. Microbial Ecology.
54(1): 112-118.
This study examined whether the proportions of two symbiotic fungi of D.
ponderosae, G. clavigerum and O. montium vary seasonally and from year to
year within populations. Bark beetles in the Montana study sites primarily carried
O. montium in their mycangia, while beetle in the Idaho study sites carried higher
percentages of G. clavigerum. G. clavigerum was carried by early-flying beetles
(associated with cooler temperatures), while O. montium was carried only by
late-flying beetles. The predicted warming climates are expected to favor O.
montium.
Abstract: In this study, we report evidence that temperature plays a key role in
determining the relative abundance of two mutualistic fungi associated with an
economically and ecologically important bark beetle, Dendroctonus ponderosae.
The symbiotic fungi possess different optimal temperature ranges. These
differences determine which fungus is vectored by dispersing host beetles as
temperatures fluctuate over a season. Grosmannia clavigera is the predominant
fungus carried by dispersing beetles during cool periods but decreases in
prevalence as daily maximum temperatures approach 25°C, and becomes
extremely rare when temperatures reach or exceed 32°C. In contrast,
Ophiostoma montium increases in prevalence as temperatures approach 25°C,
and becomes the predominant symbiont dispersed when temperatures reach or
exceed 32°C. The possession of different optimal growth temperatures may
facilitate the stable coexistence of the two fungi by supporting growth of each
fungus at different times, minimizing direct competition. Furthermore, the beetle
may reduce its risk of being left aposymbiotic by exploiting not one, but two
symbionts, whose combined growth optima span a wide range of environmental
conditions. The possession of multiple symbionts with different temperature
tolerances may allow the beetle to occupy highly variable habitats over a wide
geographic range. Such temperature-driven symbiont shifts are likely to have
major consequences for both the host and its symbionts under current
temperature regimes and those predicted to occur because of climate change.
Six, DL., Paine, T.D. 1997. Ophiostoma clavigerum is the mycangial
fungus of the Jeffrey pine beetle.
This study isolated and identified the mycangial fungi of D. jeffreyi through a
series of tests, including growth at differing temperatures and compared it to the
associated fungi of D. ponderosae, O. clavigerum and O. montium. O.
clavigerum grew best at a temperature between 21 and 27°C, while O. montium,
though initially growing slower than O. clavigerum, was able to thrive at
temperatures exceeding 27°C, and still able to grow at 32°C, a temperature at
which nearly all growth of O. clavigerum had ceased.
Abstract: Dendroctonus jeffreyi and D. ponderosae are sibling species of bark
beetles (Coleoptera: Scolytidae) with few morphological and molecular genetic
differences. The two species are believed to have diverged relatively recently.
Dendroctonus jeffreyi colonizes only Pinus jeffreyi, while D. ponderosae
colonizes up to thirteen Pinus spp., but not P jeffreyi. Adult beetles of both D.
jeffreyi and D. ponderosae carry symbiotic fungi in mycangia located on the
maxillary cardines. Dendroctonus ponderosae was known to carry two fungi,
Ophiostoma clavigerum and 0. montium, in its mycangia. However, it was not
known which fungi might be carried by D. jeffreyi. Fungi were isolated from the
mycangia of over 900 D. jeffreyi collected from a large portion of its geographic
range. Using morphology, isozyme phenotypes, and growth rates at different
temperatures, all isolates from D. jeffreyi mycangia were determined to be 0.
clavigerum; 0. montium was never isolated from D. jeffreyi mycangia.
Six, D.L., Paine, T.D. 1998. Effects of mycangial fungi and host tree
species on progeny survival and emergence of Dendroctonus ponderosae
(Coleoptera: Scolytidae). Environmental Entomology, 27(6): 1393-1401.
This paper studied the effects of mycangial fungi Ophiostoma clavigerum and
Ophistoma montium on progeny survival and emergence of Dendroctonus
ponderosae. Results suggest that O. clavigerum is mutually symbiotic with D.
ponderosae, while O. montium may actually have no positive benefits for, or is
even parasitic to, the mountain pine beetle. This is indicated by the low brood
survival, low reemergence, and slower development seen in beetle with proximity
only to O. montium than those only in proximity to O. clavigerum.
Skov, KR, Kolb, TE, Wallin, KF. 2004. Tree size and drought affect
ponderosa pine physiological response to thinning and burning
treatments. Forest Science 50: 81-91.
This study compares the influence of restoration thinning and burning treatments
on water, carbon, and nutrient relations of presettlement and postsettlement
ponderosa pines. Ponderosa pine forests of northern Arizona are unnaturally
dense as the result of fire suppression and overgrazing, among other factors.
Pre-settlement and post-settlement pine trees in these forests respond differently
to experimental thinning and burning. Water stress was unusually severe in
2000, leading to more pronounced benefits from thinning in post-settlement trees
than pre-settlement trees.
Smith, D.M., Cusack, S., Colman, A.W., Folland, C.K., Harris, G.R., Murphy,
J.M. 2007. Improved surface temperature prediction for the coming
decade from a global climate model. Science 317: 796-799.
This paper assessed the accuracy of an improved global surface temperature
(Ts) model, Decadal Climate Prediction System (DePreSys) using a set of 10year hindcasts. After proving to be generally reliable, DePreSys predicted further
Ts warming in the decade of 2004-2014, with 2014 Ts up 0.30° +/- 0.21°C. For at
least half of the years following 2009, Ts was predicted to be the highest on
record.
Solheim H, Krokene P. 1998. Growth and virulence of mountain pine beetle
associated blue-stain fungi, Ophiostoma clavigerum and Ophiostoma
montium. Canadian Journal of Botany 76: 561-566.
This paper studied two strains of blue-stain fungi, Ophiostoma clavigerum and
Ophiostoma montium grown in three different media to determine their relative
virulence and to test whether tolerance to low oxygen levels and rapid growth
can explain differences in virulence. O. clavigerum and O. montium, are
associated with the mountain pine beetle, as they are transported to new host
trees through the beetles’ mycangia. Of these two strains, O. clavigerum is
considered the more virulent, able to grow in low-oxygen environments, and at
temperatures below 25°C. O. montium, while less tolerant of low-oxygen
environments, is best able to grow at 25°C, and continues to grow until
temperatures exceed 37°C.
Somme, L. 1964. Effects of glycerol on cold hardiness in insects.
Canadian Journal of Zoology 42: 87-101.
This study examined several insect species for the formation of glycerol as
protection from cold induced mortality as temperatures decrease. Freezing injury
causes mortality in the majority of insects. As protection against cold, insects
lower their supercooling point by producing glycerol. Glycerol content follows
seasonal patterns, increasing in the fall and continuing until diapauses is broken.
Stamp, N. 2003. Out of the quagmire of plant defense hypotheses. The
Quarterly Review of Biology 78: 23-55.
This paper studied four hypotheses of plant defense: optimal defense, carbonnutrient balance, growth rate, and growth-differentiation balance. The growthdifferentiation balance (GDB) posits that plants balance allocation of resources
between differentiation-related processes (including defense through secondary
metabolism), and growth-related processes (cell reproduction and elongation).
GDB assumes that resource limitation has a greater effect on growth rates than
photosynthesis, and growth processes and secondary metabolism compete for
photosynthates. When an environment is resource-rich, plant strategy will favor
growth-related processes, while in an environment that is resource-limited, plant
strategy will favor differentiation-related processes.
Stephenson, N.L. 1990. Climatic control of vegetation distribution: the role
of the water balance. American Naturalist 135: 649.
This paper studies the correlation between the distribution of North American
plant formations and two water balance parameters, evapotranspiration and
deficit-Traditional analyses of vegetation type and climate look at annual energy
and water balances, as opposed to seasonal balances. Examining water and
energy balances seasonally, as well as distinguishing between precipitation and
actual water supply, results in striking correlation between vegetation
distributions and water supply. This correlation allows for more accurate
modeling than traditional climate and vegetation models, which relied on such
parameters as precipitation and temperature.
Stevens, R.E., Flake, Jr., H,W., 1974. A roundheaded pine beetle outbreak
in New Mexico: associated stand conditions and impact. USDA Forest
Service, Rocky Mt. For. Range Exp. Stn. Res. Note RM-259. 4 pp.
This paper examined the sizes and age classes of trees attacked during a recent
roundheaded pine beetle outbreak as well as stand conditions and species
composition prior to and after the outbreak. A roundheaded beetle outbreak in
the Sacramento Mountains of New Mexico caused 10-50% ponderosa pine
mortality in effected stands. Stands with more tree species diversity suffered
less severe ponderosa pine mortality.
Abstract: Mycorrhizae play a key role in ecosystem dynamics, and it is important
to understand how environmental stress and climate change affect these
symbionts. Several climate models predict that the intercontinental western
United States will experience an increase in extreme precipitation events and
warming temperatures. In 1996, northern Arizona, USA, experienced a 100-year
drought that caused high local mortality of pinyon pine (Pinus edulis), a dominant
tree of the southwest. We compared trunk growth, water potentials, and
ectomycorrhizal dynamics for surviving trees at three high-mortality sites and
adjacent low-mortality sites. Four major patterns emerged. First, surviving trees
at sites that suffered high mortality exhibited reduced long-term growth and
increased water stress relative to adjacent sites where little or no mortality
occurred. Second, surviving trees from high-mortality sites had 50% lower
ectomycorrhizal colonization and showed a pronounced shift in fungal community
composition relative to low-mortality sites. Third, in support of an intermediatehost plant stress hypothesis, trees that experienced intermediate levels of stress
supported two-fold greater ectomycorrhizal colonization than trees at the high or
low end of a stress gradient. Fourth, we observed a strong correlation between
trunk growth and ectomycorrhizal colonization and validated the resulting
regression model with independent data. This relationship suggests that tree
rings can be used to reconstruct past and predict future ectomycorrhizal
colonization. Overall, our findings suggest that predicted climate changes might
be accompanied by both qualitative and quantitative changes in ectomycorrhizal
dynamics that could affect ecosystems by altering nutrient cycling, carbon
dynamics, and host-plant performance.
Swaty, R.L., Deckert, R.J., Whitham, T.G., Gehring, C.A. 2004.
Ectomycorrhizal abundance and community composition shifts with
drought: Predictions from tree rings. Ecology 85: 1072-1084.
This study looked at the relationships between ectomycorrhizal fungi associated
with pinyon pine (Pinus edulis), and water stress in forests in northern Arizona.
Rates of trunk growth over the fifteen years prior to the study indicated chronic
water stress. 1996 witnessed a 100-year record drought, followed in 2002 by the
most severe drought in recorded history, causing high ratios of mortality in pinyon
pine, and decreasing ectomycorrhizal fungi colonization.
Tauber, M.J., Tauber, C., Masaki, S. 1986. Seasonal Adaptations of Insects.
Oxford University Press, New York.
This book focuses on adaptive seasonality using diapause as the primary
mechanism for synchronization of life cycle timing and temperature dependent
developmental processes. Seasonal adaptations are tied to growth, reproduction
and longevity and influence both interspecific and intraspecific interactions.
Diapause allows insects to survive harsh environmental conditions, synchronize
resource availability, and mating.
Tebaldi, C., Hayhoe, K., Arblaster, J.M., Meehl, G.A. 2006. Going to the
extremes. An intercomparison of model-simulated historical and future
changes in extreme events. Climatic Change 79: 185-211.
This paper used the comparison of historical simulation results to observed
trends and the modeling of ten extreme climate indices relating to temperature
and precipitation to determine the emergence of several significant trends
regarding future extreme climate events. Frost days will decrease, especially in
high latitudes of North America, extreme temperature range will decrease,
growing season will increase, precipitation over 10mm in a single weather event
will increase, dry days will increase, and five-day precipitation will increase.
Tran, J.K., Ylioja, T., Billings, R.F., Regniere, J., Ayres M.P. 2007. Impact of
minimum winter temperatures on the population dynamics of
Dendroctonus frontalis. Ecological Applications 17(3): 882-899.
This study examined the cold tolerance to determine if minimum winter
temperatures affect population dynamics in the southern pine beetle
Dendroctonus frontalis. An air temperature drop to -16°C was likely to result in a
65% reduction in population, while temperatures of -20°C would likely lead to an
80% decline. Prepupae were found to be the most cold tolerant of life stages,
though the mechanism for this tolerance is unknown.
USDA Forest Service. 1997. Forest Insect and Disease Conditions in the
United States 1996. Washington (DC): USDA Forest Service, Forest Health
Protection.
This report summarizes both native and non-native insect and disease conditions
in forested areas, seed orchards, and nurseries in the United States for the year
1996. Bark beetle (and other insect) infestations and weather condition trends
are given for the current year and for the years preceding insect activityalong
with a summary of activity by pathogen, region, and host.
Introduction: This is the 46th annual report prepared by the U.S. Department of
Agriculture, Forest Service, of the insect and disease conditions of the Nation’s
forests. This report responds to direction in the Cooperative Forestry Assistance
Act of 1978, as amended, to conduct surveys and report annually on insect and
disease conditions of major national significance in 1996. Insect and disease
conditions of local importance are reported in regional and state reports. The
report describes the extent and nature of insect and disease-caused damage of
national significance in 1996. As in the past, selected insect and disease
conditions are highlighted in the front section of the report. Maps are provided for
some pests showing affected counties in the East and affected areas in the
West. Graphs are provided for some pests showing acreage trends over the last
several years. Also provided are tables showing acreages affected for selected
pests by state by year for the last five years.
USDA Forest Service. 2004. Forest insect and disease conditions in the
southwestern region, 2003. R3-04-02. U. S. Department of Agriculture,
Forest Service, Southwestern Region.
This report used aerial and ground surveys to determine the status of insects and
diseases in the forests of Arizona and New Mexico. Millions of acres of forest
were surveyed in 2003 in response to the drought-driven pinyon ips (Ips
confuses) epidemic. Pinyon pine mortality was found on 1,914,345 acres, a
dramatic increase from previous years, with most damage occurring in northern
New Mexico and northern and central Arizona.
Abstract: Insects and diseases act as both indicators and regulators of the
condition (health) of southwestern forests. This has been abundantly clear in
recent years, as extreme drought conditions have resulted in the highest level of
bark beetle activity seen in several decades, dramatically affecting forest
conditions in many parts of the region.
This report summarizes the current known status of insects and diseases in the
forests of Arizona and New Mexico. Most of the insect information is based on
annual aerial detection surveys. Most of the disease information included in this
report is based on ground observations and surveys. Bark beetles and defoliating
insects cause sudden, visually dramatic damage readily seen from the air, while
most pathogens cause gradual, insidious damage that is less easily detected.
This year’s report includes results from special surveys flown over much of the
woodland type in Arizona and New Mexico, in response to the massive die-off of
piñon at many locations.
Bark beetles—the primary tree killers in the region—tend to be host specific.
Moreover, most conifers (excluding ponderosa pine) are normally attacked and
killed by a single species of bark beetle. A group of recent Douglas-fir “faders,”
for example, is most often a result of attack by the Douglas-fir bark beetle,
Dendroctonus pseudotsugae. In contrast, ponderosa pines are attacked and
killed by several different bark beetles. Thus, ground surveys may be needed to
confirm the species responsible for ponderosa pine mortality seen from the air.
Where ground checking is not conducted, assignment of causal species is based
on previous history/experience for a given location.
This report also includes a record of technical assistance provided by Arizona
and New Mexico zone personnel and brief descriptions (abstracts) of several
special activities conducted in 2003. Much of the information for State and private
lands was provided through our State Cooperative Forest Health Program.
Van Dyke, E.C. 1949. The origin and distribution of the Coleopterous insect
fauna of North America. Proceedings of the Sixth Pacific Science Congreso
of the Pacific Science Association. Vol. IV.
This paper describes the origins and current distribution of the Coleopterous
insect fauna in the four main zones in North America. Origins of the North
American Coleopterous fauna can be linked to South America through the chain
of Central American states. The current distribution of Coleopterous has been
determined by various geological, geographical, and climate changes that have
occurred since the Tertiary period.
Veblen, T.T., Hadley, K.S., Reid, M.S., Rebertus, A.J. 1991. The response of
subalpine forests to spruce beetle outbreak in Colorado. Ecology 72(1):
213-231.
This paper studied six areas affected by spruce beetle outbreaks to determine
the effects on stand composition and dominance, age and size structure, tree
growth, and succession. Probability of severe disturbance by spruce beetle is
increased by the post-wildfire development of old-growth spruce-fir stands.
Beetle outbreaks in turn lead to the release and accelerated growth of previously
suppressed fir and spruce, as opposed to new seedling establishment, leading to
a shift from spruce-dominated to fir-dominated forests.
Veblen, T.T., Hadley, K.S., Nel, E.M., Kitzberger, T., Reid. M., Villalba, R.
1994. Disturbance Regime and Disturbance Interactions in a Rocky
Mountain Subalpine Forest. The Journal of Ecology 82(1): 125-135.
This study examined how past landscape disturbances impart heterogeneity to
the forest and influence the subsequent pattern and consequence of disturbance.
Beetle outbreaks are limited in part by the role of other large-scale forest
disturbances, such as fire and avalanche. Fire and avalanche disturbances can
remove appropriate host trees from a system, preventing epidemic outbreaks of
bark beetles for as long as 70 years.
Vité, J.P. 1961. The influence of water supply on oleoresin exudation
pressure and resistance to bark beetle attack in Pinus ponderosa.
Contributions of the Boyce Thompson Institute 21:37–66.
This paper addressed the relationship between changes in oleoresin exudation
pressure and water stress in Pinus ponderosa and the impact on defense against
bark beetle attacks. The success of a bark beetle attack on ponderosa pine is in
part dependent upon water stress in the tree. Oleoresin pressure partially
determines defense of the tree and thus susceptibility to attack. Increased
transpiration due to warm weather, low humidity, and long-term water stress such
as drought reduces turgidity of the tree cells, resulting in lower oleoresin pressure
and higher susceptibility to beetle attack.
Vitousek, P.M., C.M. D’Antonio, L.L. Loope, M. rejmanek, R. Westbrooks.
1997. Introduced species: a significant component of human-caused
global change. New Zealand Journal of Ecology 21: 1-16.
This study describes the extent of global biological invasion and the interactions
between biological invasions and other components of global change. Invasive
species are closely related to several human-caused global environmental
changes, including increasing concentrations of CO2 and other greenhouse
gases. Global environmental climate change in turn results in the loss of
biodiversity through extinction as population dynamics shift.
Wang, K-Y., Kellomäki, S., Li, C., Zha, T. 2003. Light and water-use
efficiencies of pine shoots exposed to elevated carbon dioxide and
temperature. Annals of Botany 92: 53-64.
This was a three year study to determine the effects of elevated CO2 and
temperature on photosynthesis under future climate change scenarios. Light-use
efficiency (LUE) and water-use efficiency (WUE) in Scots pine trees varied
markedly in response to elevated carbon dioxide (EC), elevated temperature
(ET), and a combination of the two (ECT), as well as seasonal time frames
(growing versus non-growing seasons). Temperature effects were greatest in
trees during non-growing seasons, while EC most affected the trees during
growing season, increasing both LUE and WUE. ECT led to increased LUE,
while reducing WUE (WUE followed expected pattern of ET only).
Ward, N.L., Masters, G.J. 2007. Linking climate change and species
invasion: an illustration using insect herbivores. Global Change Biology
13(8): 1605–1615.
This paper examines factors such as diet, phenotypic plasticity, life-cycle
strategies, and changes in resource/niche availability of invasive insect species
that may impact their ability to expand their range as a result of climate change.
Phenotypically plastic non-native species not dependent on close phenotypical
synchrony are successful invaders. Climate change positively impacts propagule
pressure, leading to the formation of a pool of these potential invaders.
Fluctuating resources within an ecosystem from disturbances (including climate
related events), or an increase in resources due to elevated CO2 levels, will give
non-natives opportunities for successful invasion. Reduced competition for
resources may also provide the opportunity for invasive species to establish
within the system.
Waring, G.L., Cobb, N.S. 1992. The impact of plant stress on herbivore
population dynamics. In, E. Bernays (ed.), Insect-plant Interactions, Vol.
IV. CRC Press, Boca Raton. Pp. 167-226.
This chapter examines a number of studies on the effects of water and nutrient
defiencies on plant-herbivore relationships related to herbivore responses to
drought, plant type and feeding guild, and plant responses such as water
potential and leaf nitrogen content. Of the four guilds studied, the woodborers
associated with conifers almost all responded positively to severe drought stress.
Severe water stress also lowers levels of terpenes and resins utilized for defense
and increases nitrogen levels beneficial to insects.
Waters, W.E. 1985. The pine-bark beetle ecosystem: A pest management
challenge. Pgs. 1–48, In: Waters, W.E., Stark, R.W., Wood, D.L. (eds.),
Integrated Pest Management in Pine-Bark Beetle Ecosystems, John Wiley
and Sons, New York.
This paper discusses the distribution and life history of three species of bark
beetle, D. brevicomis, D. ponderosae, and D. frontalis which often determine the
successional pattern and character, through size, distribution, and abundance of
trees, in pine ecosystems. In regard to lodgepole pine, regardless of whether the
beetle attacked minor, dominant, or climax seral type stands, in all cases
associated tree species, undergrowth, or regeneration pine replaced the
lodgepole, notably changing stand dynamics with change being greatest in
climax type stands.
Watt, A.D., MacFarlane, A.M. 2002. Will climate change have a different
impact on different trophic levels? Phenological development of winter
moth Operophtera brumata and its host plants. Ecological Entomology 27
(2): 254–256.
This study examines the impact of climate change on the relationship between
the winter moth and Sitka spruce and oak two of its major hosts. There is general
agreement that climate change will disrupt old patterns of phonological
synchrony between insects and their host plants . Climate warming may disrupt
synchrony through the absence of winter chilling required for larval emergence.
Werner, R.A., Holsten, E.H. 1985. Factors influencing generation times of
spruce beetles in Alaska. Canadian Journal of Forest Research 15(2): 438443.
This paper studied the environmental factors that influence the rate of
development for the spruce beetle Dendroctonus rufipennis and determine a universus multi-voltinism life cycle. A phloem temperature threshold of 16.5°C is
needed during instars I and II for univoltinism. South aspect trees are most likely
to experience these temperatures. If the minimum temperature is not met, the
beetle will continue on a two-year life cycle.
Werner, R.A., Hastings, F.L., Holsten, E.H., Jones, A.S. 1986. Carbaryl and
lindane protect white spruce from attack by spruce beetles (Coleoptera:
Scolytidae) for three growing seasons. Journal of Economic Entomology
79(4): 1121-1124.
This study reports on the effectiveness of carbaryl, an alternative environmentally
safe insecticide, against spruce beetle attack in south-central Alaska at
concentrations of 1 and 2%. Although lab tests had suggested otherwise, field
tests found 2% carbaryl effective for protecting trees from infestation for 27
months. The duration of protection may increase in cold or cloudy weather.
Werner, R.A., Holsten, E.H., Matsuoka, S.M., Burnside, R.E. 2006. Spruce
beetles and forest ecosystems in south-central Alaska: A review of 30
years of research. Forest Ecology and Management 227: 195-206.
This study summarizes the research on spruce beetles from the past 30 years
including biology and ecology, host susceptibility and resistance, and
management strategies. Climatic conditions can trigger increased reproduction
and dispersal of bark beetles. In south-central Alaska, rising temperatures from
1980 onward resulted in 1-year life cycles of spruce beetle, contributing to the
massive outbreak of beetle infestation in the region, which peaked in 1996. An
estimated 30 million trees per year were being killed in the 1990s.
Westerling, A.L., Hidalgo, H.G., Cayan, D.R, Swetnam, T.W. 2006. Warming
and earlier spring increase western U.S. forest wildfire activity. Science
313: 940-943.
This study examines climate change as the primary cause of the recent increase
in summer wildfires which have traditionally been attributed to land management
practices. Analysis of Northern Rockies climate records with wildfire history
shows early spring snowmelt corresponds to increased wildfire activity. Since
the mid-1980s spring snowmelt has occurred earlier, summer temperatures have
risen, and the fire season has increased by 78 days.
Western Forestry Leadership Coalition. 2007. Western Bark Beetle
Assessment: A Framework for Cooperative Forest Stewardship.
This paper presents the current information on bark beetle outbreaks and
provides a map of active forest management areas, management techniques,
and identifies groups with the resources to manage bark beetle outbreaks. As a
result of bad forest management or lack thereof, western US forests exhibit
unhealthily high densities and hazardous fuel buildup. Surface fuel is increased
through beetle infestations, which cause large trees to fall, increasing the severity
of wildfires at the surface level and severely impacting soil, water, and other
public values. Active forest management is needed to reduce susceptibility to
epidemic beetle populations, to protect the ecological, economic, and social
systems western forests support.
Whitney, H.S. 1971. Association of Dendroctonus ponderosae
(Coleoptera: Scolytidae) with blue stain fungi and yeasts during brood
development in lodgepole pine. The Canadian Entomologist 103: 14951503.
This report examines the mutualism between Dendroctonus ponderosae and its
assoaciated blue stain fungi and yeasts reared under laboratory conditions. Ten
or more broods of mountain pine beetle were examined each year from 19651967, and all broods contained C. montia and at least one yeast. Movement by
the female during egg-laying helped in distributing propagules of these
microorganisms throughout the gallery although the terminus of some galleries
was axenic. Evidence supports the hypothesis of mutualism between D.
ponderosae and its associated yeasts and fungi.
Williams, D.W., Liebhold, A.M. 1997. Latitudinal shifts in spruce budworm
(Lepidoptera: Tortricidae) outbreaks and spruce-fir forest distributions with
climate change. Acta Phytopathologica et Entomologica Hungarica 32(1-2):
205-215.
This paper analyzed maps of historical spruce beetle outbreaks in the eastern
United States to develop a model and extrapolate the future distribution of spruce
forests under three climate change scenarios. Rising temperatures will result in
increased evapotranspiration and metabolic costs in many spruce forests.
Increasing pressure from defoiliators which can rapidly expand their range may
cause spruce populations existing in lower latitudes and elevations to die out.
Wood, D.L. 1972. Selection and colonization of ponderosa pine by bark
beetles. Pgs. 101–117, In: van Emden, H.F. (ed.), Insect/plant Relationships,
Blackwell Scientific Publications, Oxford.
This paper uses the western pine beetle/ponderosa pine complex as a model to
study the host selection and colonization processes employed by bark beetles.
Bark beetles are a primary species, attacking and killing their hosts to reproduce.
After wounding by the initial attackers, yeasts introduced begin tp produce a
secondary attractant which results in aggregation and concentrated attack which
kills the tree.
Wood, D.L. 1982. The role of pheromones, kairomones, and allomones in
the host selection and colonization behavior of bark beetles. Annual
Review of Entomology 27:411–446.
This paper discusses the chemical strategies used by bark beetles such as
pheromones, allomones, and kairomones to communicate regarding new host
trees. The host selection process has four stages: dispersal, selection,
concentration, and establishment. Pheromone production begins with feeding or
boring during the concentration phase, though it is not certain wheter feeding is a
requirement for initiation of pheromone production in bark beetles.
Wood, S.L. 1982. The bark and ambrosia beetles of North and Central
America (Coleoptera: Scolytidae): A taxonomic monograph. Great Basin
Naturalist Memoirs No. 6, 1359 pp.
This volume details the biological activities, economic impacts, geography, and
classification of the Scolytidae of North and Central America. Dendroctonus spp.
has a wide range and distribution with D. frontalis found along the entire east
coast as well as in Arizona and New Mexico. D mexicanus and D. vitei are found
as far south as Honduras and Guatemala. 10 of the 17 Dendroctonus spp. are
found in Central and South America.
Wood, S.L. 1985. Aspectos taxonomicos de los Scolytidae. Pp 170-174. In
Proceedings 2nd National Symposium Forest Parasitology Cuernavaca
Morelos, Mexico 17-20 February 1982. Secrataria de Recursos Hidraulicos
Publicacion Especial No. 46. Mexico City, Mexico.
Woodward, F.I., Williams, B.G. 1987. Climate and plant distribution at
global and local scales.
This paper examines temperature and precipitation as the major mechanisms
that determine the abundance and distribution of vegetation. Universal
correlations exist between distribution of vegetation and temperature and
precipitation. Leaf mass may be predicted by the hydrological budget, as an
increase in water will lead to increased leaf growth and thus mass. Annual
minimum temperature acts as a limit to vegetation types, though these limits
differ with varying population dynamics within individual species.
World Metrological Organization. 2006. The state of greenhouse gases in
the atmosphere using global observations through 2005. Greenhouse gas
bulletin. http://www.wmo.int/ pages/prog/arep/gaw/ghg/ghgbull06_en.html.
This bulletin reports on the trends and current levels of the major greenhouse
gases (GHGs); carbon dioxide, methane, and nitrous oxide as well as
chloroflourocarbons (CFCs). Atmospheric GHG concentrations reached new
highs in 2005 with CO2 at 379.1 ppm, 35.4% higher than its historic pre-industrial
concentration. CO2 is responsible for 62% of total radiative forcing (90% in the
past decade), and is the single most important infrared absorbing anthropogenic
greenhouse gas. Emissions come primarily from combustion of fossil fuels, and
to a lesser extent, deforestation.
Yuill, J.S., 1941. Cold hardiness of two species of bark beetles in California
forests. Journal of Economic Entomology 34, 702-709.
This study focused on the effects of cold temperature on bark beetle mortality
determining the low temperature threshold for survival, length of exposure, and
the impact of host selection on cold hardiness. The mountain pine beetle and
western pine beetle are both susceptible to freezing, but cold hardiness acts
differently in each. Overwintering larvae of the western pine beetle are killed by
a temperature range of 5 to -7.5°F, and are more cold-hardy in winter season
than summer; western pine beetle experience a quick and distinct, though small,
shift from summer cold-hardiness to winter cold-hardiness.
Zaslovski, V.A. 1988. Insect development: photoperiodic and temperature
control. Springer-Verlag, Berlin.
This book covers the topic of photoperiodic and temperature control of insect
development including the induction and termination of diapause. It was
proposed that diapause has two phases, the initial period of quiescence and a
subsequent activation phase in which insects are predisposed to the resumption
of development when a temperature and/or photoperiodic threshold is reached.
Cold-hardiness achieved during diapause is irreversibly lost after only a few days
at 25°C in Pterostichus aethiops and Phosphuga atrata.
Zausen, G.L., Kolb, T.E., Bailey, J.D., Wagner, M.R. 2005. Long-term
impacts of stand management on ponderosa pine physiology and bark
beetle abundance in northern Arizona: A replicated landscape study.
Forest Ecology and Management 218: 291-305.
This was a study examined forest management through prescribed burning and
thinning and the impact on oleoresin flow, phloem thickness, radial growth and
bark beetle abundance. Ponderosa pine in the mid-elevation forests of northern
Arizona were found to have exceptional resistance to bark beetles during years
of water stress.
Zeneli, G., Krokene, P., Christiansen, E., Krekling, T., Gershenzon, J. 2006.
Methyl jasmonate treatment of mature Norway spruce (Picea abies) trees
increases the accumulation of terpenoid resin components and protects
against infection by Ceratocystis polonica, a bark beetle-associated
fungus. Tree Physiology 26:977–988.
This study examined the effects of methyl jasmonate on the terpenoid and
phenolic defenses and resistance to blue stain fungi in mature Norway spruce.
When treated with high dosages of methyl jasmonate, Norway spruce (Picea
abies), will massively increase production of traumatic resin ducts. External resin
flow will also increase, simulating defenses to mechanical wounding, beetle
attack, or fungal inocculation.
Zúñiga G., Cisneros R., Hayes J.L., Macias-Samano J.E. 2002. Karyology,
geography distribution and origin of the genus Dendroctonus Erichson
(Coleoptera: Scolytidae). Annals of the Entomological Society of America
95: 267-275.
This study utilized available karyological data to analyze the chromosomal
diversity of Dendroctonus populations and chromosomal evidence to examine
their hypothesized Mexican origin. There are two hypotheses of origin proposed
for the modern genus Dendroctonus that are counter to the preexisting
hypothesis of a Mexican origin, both based from evidence derived from genetic
evolution and diversification. The first assumes that, as the genus dispersed
from northern North America toward Eurasia and southward in North America,
karyotypic diversification occurred from centric fusion and fission of an original
karyotype between 18 and 22 chromosomes. The second assumes karyotypic
diversification occurred as a diversified Dendroctonus followed the north to south
movement of its host genus, Pinus.
Zvereva, E.L., Kozlov, M.V. 2006. Consequences of simultaneous elevation
of carbon dioxide and temperature for plant-herbivore interactions: A
metaanalysis. Global Change Biology 12: 27-41.
This study employed metaanalyses to determine the effects of elevated CO2 and
temperature both together and separately on the response of herbivores and
plant characteristics that are important to herbivores. The metaanalyses
considered studies reporting Nitrogen, carbon-based secondary compounds (an
indicator of plant chemical defense), phenolics and terpenes. Gymnosperm N
decreased under combined elevated CO2 and temperature, and in gymnosperm
woody tissue, chemical defense as indicated by carbon-based secondary
compounds increased, terpenes increased, while phenolics decreased.
Interactive elevated CO2 and temperature significantly decreased quality of
gymnosperms as food for herbivore insects.