Abstracts of all talks and posters presented at AGU 2014 in the two CIRMOUNT sessions.
Session 1: Responses of Alpine and Arctic Treeline Ecotones to Environmental Change
TALKS
The Role of Topoclimate in Explaining Abrupt Growth Thresholds of Bristlecone Pine in the White Mountains of California,
USA
Andrew G Bunn, Matthew W Salzer, Evan R Larson, Stuart B Weiss and Malcolm K Hughes
We present data on growth of approximately 100 individual bristlecone pine (Pinus longaeva) trees situated at and near upper treeline
in the White Mountains of California. Most trees growing at treeline show positive trends in growth in the 20th century and vary with
temperature at both decadal and interannual timescales. However, many trees situated just 50 m or more below treeline have growth
patterns that do not correlate strongly with the trees from the highest elevations. Some of these growth disparities can be explained by
understanding the role of topography (including nighttime cold air pooling) at the scale of tens of meters. In particular, trees growing
below treeline but in the coldest locations of the hillslope track temperature variations. Conversely, the fast growth of some of the
highest trees in the warmest biophysical settings has declined since the mid-1980s. This might suggest that the climate response of
trees has recently shifted from being positively to negatively associated with temperature.
Wind-Snow Interactions and Treeline Advance in the Medicine Bow Mountains, Wyoming: A Coupled Examination Using
Dendroecology and Remote Sensing
Grant Elliott and Christopher J Crawford
Research suggests that broad-scale increases in temperature facilitated an abrupt initiation of upper treeline advance beginning in the
1950s at climatic treelines throughout a large portion of the southern and central Rocky Mountains. Despite this regional trend, patterns
of finer scale variability often imply the likely influence of both wind-snow interactions and temperature on driving regeneration
dynamics in these climatically-sensitive ecotones. This is particularly true for mountain ranges subject to consistently strong winds,
such as the Medicine Bow Mountains of southeast Wyoming. A rich history of treeline work exists for this area, yet questions remain
regarding how influential wind and snowpack variability are in governing climate-vegetation interactions within upper treeline ecotones
and whether this varies according to the level of wind exposure. Here we present a coupled examination using dendroecology and
remote sensing to test the hypothesis that sufficient snow cover is required in order for the ecological manifestation of increasing
temperatures to appear at upper treeline; namely treeline advance. We used dendroecological methods to reconstruct the history of
colonization on the two highest peaks in the range (Medicine Bow Peak Massif and Kannaday Peak). We sampled a total of six sites by
placing nested-belt transects on two south-facing and one north-facing site for each peak. To gauge the influence of wind-snow
interactions at each site, we analyzed remotely-sensed images. We selected three sets of LANDSAT images for each mountain peak
based on years with maximum, minimum, and mean snowfall conditions to capture the entire range of variability. Results demonstrate
that snow cover can be a critical modifier of treeline advance, especially on wind-exposed slopes and on mountain peaks with a
relatively dry hydroclimatology, where a protective snow layer is only evident during high snow years. Overall, this research suggests
that the role of wind-snow interactions in mediating upper treeline advance is contingent on local hydroclimatology and that future
changes in these environments will most likely be driven by changes in both temperature and snowpack conditions.
Do Small Mammals and Vegetation Metacommunity Dynamics Determine the Extent and Pattern of Treeline in the High
Elevation Zone of the Sierra Nevada Mountain Range?
Robert Charles Klinger and Jennifer T Chase
There has been a general expectation that warming temperatures will facilitate transformation of high elevation meadows to woody
dominated communities. We have been using observational and experimental approaches to analyze potential state changes of
meadows and the role seed and seedling predation play in conifer expansion in the high elevation zone of the Sierra Nevada mountain
range of the western United States. The observational component consists of 256 plots spanning 3 degrees of latitude and an elevation
range from 3000 m to 4000 m. The experimental component consists of mammal seed predator exclosures (N = 252) allocated among
three arrays at each of two sites separated by > 100 km. Three cohorts of seeds at five seed densities (1, 2, 3, 5 and 10 seeds per 0.25
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m ) and one seedling cohort were placed within and immediately outside the exclosures at each site. Trend surface and distance decay
analyses of community composition indicate vegetation communities in the high elevation zone have not assembled predictably along
environmental or spatial gradients. Rather, we have found strong support for neutral dynamics, implying that communities assemble
more stochastically as a result of dispersal limitation or priority effects. Density of mature and sapling conifers decrease as a function of
distance from conifer patches, but seedling density has no relationship with distance from conifer patches. Germination of seeds
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outside of the exclosures was 19% compared to 65% within, and these were mainly at densities of 1 seed per 0.25 m . None of the
seeds that germinated outside the exclosures survived more than 1.5 years compared to 23% within the exclosures. Virtually all of the
seedlings planted outside the exclosures were removed within a year. Collectively, these findings indicate a highly patchy rather than
uniform pattern of treeline extension in the high elevation zone of the Sierra Nevada. Moreover, smaller mammals appear to be playing
a critical role in slowing or decoupling colonization of conifers into high elevation meadows and other vegetation types.
Recruitment of subalpine tree populations sensitive to warming within and above current altitudinal range
Lara M Kueppers, Cristina Castanha, Andrew B Moyes, Erin Conlisk, Matthew J Germino, Margaret S Torn, John Harte and
Jeffry Mitton
Forests are globally important contributors to carbon storage and release, and have strong regional leverage on surface energy balance
and water fluxes. Highly uncertain feedbacks to climate change from dynamic shifts in forest distributions are increasingly incorporated
into Earth system models, but lack data for parameterizations and quantitative benchmarks. We established the Alpine Treeline
Warming Experiment at Niwot Ridge, CO, to examine effects of climate warming on tree seedling establishment near the lower limit of
subalpine forest, at upper treeline, and in the alpine. We use infrared heaters to increase surface temperatures, and to lengthen the
growing season. We also watered some plots to distinguish effects due to higher temperatures from those due to drier soil. We used
meta-population models parameterized with data from the experiment and from the literature to assess impacts of warming on tree
population sizes over time.
Averaged over 4 years, heating elevated soil temperatures, slightly reduced soil moisture, and advanced snowmelt. Heated and
watered plots were not systematically wetter or drier than controls, as intended. Preliminary analyses show that in the forest, heating
reduced germination for two species and, in most years, had no or negative effects on survival to 2 years, while watering increased
demographic rates, consistent with expectations of reduced recruitment at lower elevations with warming and drying. At treeline,
heating also reduced germination, but had year-dependent effects on survival to 2 years. In the alpine, contrary to expectations,
experimental heating did not increase germination or survival, while watering increased survival to two years. Changing the seedling
survival consistent with our experiment, and keeping all other parameters constant, we found strong effects of heating and watering on
modeled population sizes. These effects vary across the three elevations. Due to timescales involved in tree growth, we find large lags
between onset of climate changes and tree population responses. Linking field experiments directly with models of population change
across the landscape provides a novel approach to projecting changes in altitudinal distributions of forest with climate change over
time.
Seedling establishment at the alpine tree line - Can there be too much winter protection?
Signe Lett, David Wardle, Marie-Charlotte Nilsson and Ellen Dorrepaal
Climate-change impacts on species distributions will be especially complex in mountain systems with steep environmental gradients
and heterogeneous landscapes. In the western US, projected climate conditions include rising temperatures, decreased snowpack, and
increased moisture deficits, all of which will impact species distributions at high elevations. Whitebark pine (Pinus albicaulis; WBP) is a
keystone species in subalpine environments and one that is highly vulnerable to projected climate trends. In the past two decades,
WBP populations dramatically declined as a result of bark beetle infestation, blister rust, high-severity fires, and drought. Species-niche
modeling used to map future WPB distributions is based on the relation between present-day occurrence and bioclimatic parameters.
While these models capture the realized niche, the full niche space inferred from paleo-observations appears to be much larger. To
assess a broad range of bioclimatic conditions for WPB, we examined its response to past changes in climate, fire activity, and species
competition. General additive modeling of pollen/charcoal data from the Greater Yellowstone area indicate that WBP reached maximum
population size and distribution ~12,000 -7500 years ago and declined thereafter. Population dynamics tracked variations in summer
insolation, such that WBP was most abundant when summer temperatures and fire frequency were higher than at present. Competition
from lodgepole pine after ~10,000 years ago limited WBP at middle elevations. Paleoecological data indicate that the fundamental WBP
niche is considerably larger than assumed, and simulations that project the demise of WBP in the next 50 years are probably too
dramatic given WPB’s ability to thrive under warm conditions and high fire activity in the past. Management strategies that reduce biotic
competition and nonnative pathogens should help increase the future resilience of WBP and other subalpine species.
Patterns of Twentieth Century Treeline Advance in Alaska: Insights from Dendrochronology and Permanent Plot Studies
Andrea H Lloyd and Christopher L. Fastie
Climate-change impacts on species distributions will be especially complex in mountain systems with steep environmental gradients
and heterogeneous landscapes. In the western US, projected climate conditions include rising temperatures, decreased snowpack, and
increased moisture deficits, all of which will impact species distributions at high elevations. Whitebark pine (Pinus albicaulis; WBP) is a
keystone species in subalpine environments and one that is highly vulnerable to projected climate trends. In the past two decades,
WBP populations dramatically declined as a result of bark beetle infestation, blister rust, high-severity fires, and drought. Species-niche
modeling used to map future WPB distributions is based on the relation between present-day occurrence and bioclimatic parameters.
While these models capture the realized niche, the full niche space inferred from paleo-observations appears to be much larger. To
assess a broad range of bioclimatic conditions for WPB, we examined its response to past changes in climate, fire activity, and species
competition. General additive modeling of pollen/charcoal data from the Greater Yellowstone area indicate that WBP reached maximum
population size and distribution ~12,000 -7500 years ago and declined thereafter. Population dynamics tracked variations in summer
insolation, such that WBP was most abundant when summer temperatures and fire frequency were higher than at present. Competition
from lodgepole pine after ~10,000 years ago limited WBP at middle elevations. Paleoecological data indicate that the fundamental WBP
niche is considerably larger than assumed, and simulations that project the demise of WBP in the next 50 years are probably too
dramatic given WPB’s ability to thrive under warm conditions and high fire activity in the past. Management strategies that reduce biotic
competition and nonnative pathogens should help increase the future resilience of WBP and other subalpine species.
Reflections on Treeline Studies and Ways to Improve Them
Bjartmar Sveinbjornsson
The opposing feedbacks to climate warming by surface albedo (positive) and carbon storage (negative) of forests, partly explains the
recent interest in understanding what controls the extent of forests while the need to understand visual patterns has long stimulated
questions and studies. Studies into the reasons for limits to forest extent have generally focused on the transition zone (treeline)
between the forest and the adjacent shrub, heath, or meadow. There, the questions have focused on two main themes, one relating to
the small size of the tree individuals (growth) and the other to their low density (reproduction and establishment). The questions thus
boil down to: Why so small?” “Why so few?” The assumption is that good answers will explain the location of the treeline.
I will address some weaknesses in our framing of the questions relating to treelines and in our approaches in answering them. What are
the major knowledge gaps and what are some ways to make future research efforts more effective? These may include the
identification of categories of treeline types and their distribution over short and long distances i.e. the need for both intensive and
extensive sites within and between mountain ranges. They may also include preliminary assessment of the temporal and spatial data
resolutions needed for generalizations. Both biotic and abiotic resources and stressors must be recognized, both in terms of direct
physical (e.g. shelter, shade) and chemical impacts (e.g. litter quality, toxic release) and the former also in terms of their indirect impact
where they serve as alternative hosts of a symbiont or a pathogen. I will point out that implicit assumptions of relevance of a factor and
the tree response patterns may be faulty and give examples of the unintended consequences of some techniques designed to
manipulate resource availability. To successfully address these shortcomings, I will discuss the benefits of multi-/inter-disciplinary
teams to sharpen the formulation of the questions, to better focus the experimental design and to enhance the engineering of
manipulations/experiments/monitoring and finally to improve the data analyses and explain the importance of the results including the
boundaries of generalization.
Subalpine Species Response to Past Climate Change and Fire Activity: Are We Underestimating the Biotic Resilience?
Cathy L Whitlock, Virginia Iglesias and Teresa Krause
Climate-change impacts on species distributions will be especially complex in mountain systems with steep environmental gradients
and heterogeneous landscapes. In the western US, projected climate conditions include rising temperatures, decreased snowpack, and
increased moisture deficits, all of which will impact species distributions at high elevations. Whitebark pine (Pinus albicaulis; WBP) is a
keystone species in subalpine environments and one that is highly vulnerable to projected climate trends. In the past two decades,
WBP populations dramatically declined as a result of bark beetle infestation, blister rust, high-severity fires, and drought. Species-niche
modeling used to map future WPB distributions is based on the relation between present-day occurrence and bioclimatic parameters.
While these models capture the realized niche, the full niche space inferred from paleo-observations appears to be much larger. To
assess a broad range of bioclimatic conditions for WPB, we examined its response to past changes in climate, fire activity, and species
competition. General additive modeling of pollen/charcoal data from the Greater Yellowstone area indicate that WBP reached maximum
population size and distribution ~12,000 -7500 years ago and declined thereafter. Population dynamics tracked variations in summer
insolation, such that WBP was most abundant when summer temperatures and fire frequency were higher than at present. Competition
from lodgepole pine after ~10,000 years ago limited WBP at middle elevations. Paleoecological data indicate that the fundamental WBP
niche is considerably larger than assumed, and simulations that project the demise of WBP in the next 50 years are probably too
dramatic given WPB’s ability to thrive under warm conditions and high fire activity in the past. Management strategies that reduce biotic
competition and nonnative pathogens should help increase the future resilience of WBP and other subalpine species.
POSTERS
The Interface Between Snowfields and Treeline at Glacier National Park, Montana
Martha E Apple, Macy K Ricketts, Lindsay G Carlson and Nicky Ouellet
Snowfields at Glacier National Park will likely retreat or disappear with climate change. GNP contains numerous snowfields previously
designated as permanent, although this designation is no longer accurate. The edge of a snowfield moves inward while melting in
summer and provides a water-rich microhabitat for alpine plants capable of growing in this harsh environment. We hypothesize that the
species distribution of alpine plants will change with the retreat or disappearance of snowfields. Small, herbaceous plants live at the
edges of snowfields, but trees and drought-tolerant, xeromorphic cushion plants may eventually inhabit the current snowfield edges.
We established permanent, geospatially referenced transects and plots in 2012-14 at the lateral and leading edges of snowfields at
Siyeh, Logan, and Piegan Passes, at Preston Park, and the Mt. Clements moraine (the outer, downslope boundary of a vast
snowfield). We used the Raunkiaer scheme to classify snowfield and proximal plants according to functional traits, the position of
overwintering buds, and overall morphology. We characterized leaf morphology; developed height-frequency profiles; determined soil
composition; and sieved soil to examine the seed bank.
The majority of the current snowfield edge plants are protohemicryptophytes, which means their buds overwinter at or just below the
ground surface, or geophytes, which means their buds overwinter farther beneath the ground. Cushion plants were found farther from
the snowfields while relatively thin-leaved (and likely less drought tolerant) plants were found near the snowfield’s edge.
Krummholz subalpine fir grows on the cliffs above the Mt. Clements snowfield, on the Mt. Clements moraine (15-20m from the
snowfield) and 20-25m from the Piegan Pass snowfield. Krummholz whitebark pine grow within 50m of the snowfield at Piegan Pass.
Non-krummnolz subalpine fir trees grow within 10m of the Preston Park snowfield’s upper edge. Trees were not found within 50m of the
Siyeh Pass snowfield, which is characterized by harsh winds and a seemingly arid scree slope. It may be that the retreat and possible
disappearance of the snowfields will open habitat that will eventually be colonized by trees, especially since these trees are currently
found very close to most of the snowfields.
Elevation, Substrate, & Climate effects on Alpine & Sub-Alpine Plant Distribution in California & Nevada's High Mountains:
Preliminary Data from the California and Nevada GLORIA Project
Adelia Barber and Connie Millar
Documenting plant response to global climate change in sensitive zones, such as the alpine, is a major goal for global change biology.
Basic information on alpine plant distribution by elevation and substrate provides a basis for anticipating which species may decline in a
warming climate. The Global Observation Research Initiative in Alpine Environments (GLORIA) is a worldwide effort to document
vegetation changes over time in alpine settings using permanent multi-summit plots. The California/Nevada group currently monitors
seven permanent GLORIA target regions, composed of 29 summits in alpine and subalpine zones. Summits range in elevations from
2918m to 4325m on substrates including dolomite, granite, quartzite, and volcanics. High-resolution plant occurrence and cover data
from the upper 10 meters of each summit are presented. Plants from our target regions can be divided into three groups: summit
specialists found only on the highest peaks, alpine species found predominantly within the alpine zone, and broadly distributed species
found in the alpine zone and below. Rock substrate and microsite soil development have a strong influence on plant communities and
species richness. We present the first set of five-year resurvey and temperature data from 18 summits. We have documented some
annual variation in species presence/absence at almost all sites, but no dramatic changes in total diversity. Consistent with the
expectation of rising global temperatures, our soil temperature loggers have documented temperature increases at most of our sites.
These data are a baseline for assessing bioclimatic shifts and future plant composition in California and Nevada’s alpine zone.
Evolutionary History Underlies Plant Physiological Responses to Global Change Since the Last Glacial Maximum
Katie M. Becklin, Juliana S Medeiros, Kayla R. Sale and Joy K. Ward
Assessing family and species-level variation in physiological responses to global change across geologic time is critical for
understanding factors that underlie changes in species distributions and community composition. Ancient plant specimens preserved
within packrat middens are invaluable in this context since they allow for comparisons between co-occurring plant lineages. Here we
used modern and ancient plant specimens preserved within packrat middens from the Snake Range, NV to investigate the
physiological responses of a mixed montane conifer community to global change since the last glacial maximum. We used a conceptual
model to infer relative changes in stomatal conductance and maximum photosynthetic capacity from measures of leaf carbon isotopes,
stomatal characteristics, and leaf nitrogen content. Our results indicate that most of the sampled taxa decreased stomatal conductance
and/or photosynthetic capacity from glacial to modern times. However, plant families differed in the timing and magnitude of these
physiological responses. Additionally, leaf-level responses were more similar within plant families than within co-occurring species
assemblages. This suggests that adaptation at the level of leaf physiology may not be the main determinant of shifts in community
composition, and that plant evolutionary history may drive physiological adaptation to global change over recent geologic time.
Can nutrient limitations explain low and declining white spruce growth near the Arctic treeline in the eastern Brooks Range,
Alaska?
Sarah Ellison and Patrick F Sullivan
The position of the Arctic treeline is of critical importance for global carbon cycling and surface energy budgets. However, controls on
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tree growth at treeline remain uncertain. In the Alaskan Brooks Range, 20 century warming has caused varying growth responses
among treeline trees, with trees in the west responding positively, while trees in the east have responded negatively. The prevailing
explanation of this trend ascribes the negative growth response to warming-induced drought stress in the eastern Brooks Range.
However, recent measurements of carbon isotope discrimination in tree rings, xylem sap flow and needle gas exchange suggest that
drought stress cannot explain these regional growth declines. Additionally, evidence from the western Brooks Range suggests that
nutrient availability, rather than drought stress, may be the proximate control on tree growth. In this study, we investigated the
hypothesis that low and declining growth of eastern Brooks Range trees is due to low and declining soil nutrient availability, which may
continue to decrease with climate change as soils become drier and microbial activity declines. We compared microclimate, tree
performance, and a wide range of proxies for soil nutrient availability in four watersheds along a west-east transect in the Brooks Range
during the growing seasons of 2013 and 2014. We hypothesized that soil nutrient availability would track closely with the strong westeast precipitation gradient, with higher rainfall and greater soil nutrient availability in the western Brooks Range. We expected to find
that soil water contents in the west are near optimum for nitrogen mineralization, while those in the east are below optimum. Needle
nitrogen concentration, net photosynthesis, branch extension growth, and growth in the main stem are expected to decline with the
hypothesized decrease in soil nutrient availability. The results of our study will elucidate the current controls on growth of trees near the
Arctic treeline, enabling improved predictions of future treeline position and more accurate reconstructions of past climate.
Effect of Shrub Cover on Spruce Seedling Establishment at and Above Alpine Treeline in the Alaska Range
Galen Fastie and Andrea H Lloyd
Shrub coverage in the arctic has significantly increased in the past 50 years. Spruce seedling establishment in areas above the upper
forest boundary has likewise increased as treeline has advanced. Little is known about the effect of shrubs on spruce seedlings near
arctic tree lines, and how shrubs may affect the advance of tree line. In order to determine the effect of these shrubs on seedling
establishment, we took measurements of shrub coverage in study plots in the Alaska Range established in the late 1990s at and above
the current treeline. At each of ten plots located at and above treeline, ten points were systematically selected, using a grid pattern, and
ten were selected at haphazardly chosen seedlings. At each point, a measurement of shrub coverage was taken, indicating the species
present at the ground level, under 25 centimeters, between 25cm and a meter, between one and two meters, and between two and four
meters, and above four meters above ground level. The data at systematic points indicates almost ubiquitous cover of shrubs in the
under 25 cm height class, 43 percent coverage between 25cm and a meter, 14.5 percent coverage between one and two meters, 2
percent coverage between two and four meters, and three percent coverage above four meters. The frequency of each shrub height
category at points with seedlings differed significantly from the frequency at the systematic points (χ2 = 26.3, p =.0000337). Points with
seedlings had less shrub coverage overall than the systematic points, particularly in the tallest height categories. The frequency of tall
shrubs in sites with seedlings was almost half that in the systematic points. Very similar patterns existed in both the tree line and above
tree line transects. These results suggest that seedlings preferentially establish in sites without tall shrubs. Shrubs may therefore limit
establishment of spruce at tree line, and continued shrub expansion may inhibit or slow tree line expansion.
The Response of Vegetation Zonation in Rocky Mountain Ecotones to Climate Change
Adrianna Foster, Jacquelyn K Shuman and Herman Henry Shugart Jr
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Mean annual temperatures in the western United States have increased in the last few decades, and during the 21 century, it is
predicted that this warming trend will continue. This change in climate may create shifts in the optimal ranges of vegetation within the
Rocky Mountains, requiring species migration. For a species at the top of a mountain there may be little room for upward migration.
These forests are a crucial part of the US’s carbon budget, thus it is important to analyze how climate change will affect the zonation
and species composition of vegetation in Rocky Mountain landscapes. UVAFME is an individual-based gap model that simulates
biomass and species composition of a forest. Originally developed for northeast China and applied across all of Russia, this model has
accurately simulated diverse forests in a range of climates, as well as the response of these forests to climate change. UVAFME is first
calibrated to several sites along the Colorado and Wyoming Rocky Mountains using species, soil, and climate data from the US Forest
Service. The initial model output of biomass and species composition is tested against forest inventory data and expected forest type
ecotone along an elevational gradient. The model is then run with a linear increase in temperature of 3°C over 200 years,
corresponding to the A1B IPPC climate scenario. These results are compared to current forest inventory data and to model runs without
climate change. We project that with climate change species ranges will shift up the mountain, leading to an increase in the deciduous
species Populus tremuloides, and a decrease in coniferous species at high elevations. These results are an important step in
evaluating the response of Rocky Mountain vegetation to climate change and will help predict the future of these crucial ecosystems.
Modeling effects of climate change on spruce-fir forest ecosystems: Changes in the montane ecotone between boreal and
temperate forests in the Green Mountains, U.S.A, from forest edge detection in Landsat TM imagery,1989 to 2011
Jane R Foster and Anthony W D'Amato
Climate change is projected to affect the integrity of forested ecosystems worldwide. One forest type expected to be severely impacted
is the eastern spruce-fir forest, because it is already at the extreme elevational and latitudinal limits of its range within the northern
United States. Large-scale bioclimactic models predict declining habitat suitability for spruce and fir species, while causing drought and
thermal stress on remnant trees. As rising temperatures reduce or eliminate habitat throughout much of the current spruce-fir range,
growth and regeneration of hardwood forests or more southerly conifers will be favored.
The ecotone between northern hardwood forests and montane boreal forests was recently reported to have shifted approximately 100
m upslope over the last 20-40 years in the Green Mountains of Vermont, U.S.A. The research behind this finding relied on long-term
forest plot data and change analysis of narrow transects (6 m width) on aerial photos and SPOT imagery. In the White Mountains of
New Hampshire, U.S.A., research using vegetation indices from Landsat data reported a conflicting finding; that coniferous vegetation
was increasing downslope of the existing ecotone. We carefully matched and topographically corrected Landsat images from 1989
through 2011 to comprehensively map the boreal-temperate forest ecotone throughout the Green Mountains in Vermont, U.S.A. We
used edge detection and linear mixed models to evaluate whether the ecotone changed in elevation over 20 years, and whether rates
of change varied with Latitude or aspect.
We found that the elevation of the boreal-temperate forest ecotone, and changes in its location over 20 years, were more variable than
reported in recent studies. While the ecotone moved to higher elevations in some locations at reported rates, these rates were at the
tales of the distribution of elevational change. Other locations showed downward movement of the ecotone, while for the majority of
sites, no change was detected. The large variability in both the rate and direction of elevational change of the boreal-temperate forest
ecotone suggests that current changes cannot be attributed clearly to climate change, but may equally reflect forest dynamics of older
forests senescing and being replaced locally by competing species.
Physiological limitation at alpine treeline: relationships of threshold responses of conifers to their establishment patterns
Matthew J Germino, Brynne Lazarus, Cristina Castanha, Andrew B Moyes and Lara M Kueppers
An understanding of physiological limitations to tree establishment at alpine treeline form the basis for predicting how this climate-driven
boundary will respond to climate shifts. Most research on this topic has focused on limitations related to carbon balance and growth of
trees. Carbon balance could limit survival and establishment primarily through slow-acting, chronic means. We asked whether tree
survival and thus establishment patterns reflect control by chronic effects in comparison to acute, threshold responses, such as survival
of frost events. Seedling survivorship patterns were compared to thresholds in freezing (temperature causing leaf freezing, or freezing
point, FP; and physiological response to freezing) and water status (turgor loss point, TLP; and related physiological adjustments).
Subject seedlings were from forest, treeline, and alpine sites in the Alpine Treeline Warming Experiment in Colorado, and included
limber and lodgepole pine (a low-elevation species), and Engelmann Spruce. Preliminary results show survival increases with seedling
age, but the only corresponding increase in stress acclimation was photosynthetic resistance to freezing and TLP, not FP. Differences
in survivorship among the species were not consistent with variation in FP but they generally agreed with variation in photosynthetic
resistance to deep freezing and to early-season drought avoidance. Mortality of limber pine increased 35% when minimum
temperatures decreased below -9C, which compares with FPs of >-8.6C, and about 1/3 of its mortality occurred during cold/wet events,
particularly in the alpine. The other major correlate of mortality is midsummer drying events, as previously reported. Also in limber pine,
the TLP for year-old seedlings (-2.5 MPa) corresponded with seasonal-drought mortality. In summary, we show several examples of
correspondence in physiological thresholds to mortality events within a species, although the relationships are not strong. Across
species, photosynthetic resistance to freezing and early-season drought avoidance related well to mortality patterns. These results are
generally more supportive of the role of chronic rather than acute climate effects in broad patterns of tree seedling establishment at
treeline.
CanTreeline Shift in Tropical Africa be Used As Proxy to Study Climate Change?
Miro Jacob, Amaury Frankl, Maaike De Ridder, Etefa Guyassa, Hans Beeckman and Jan Nyssen
The important ecosystem services of the vulnerable high altitude forests of the tropical African highlands are under increasing
environmental and human pressure. The afro-alpine treeline forms an apparent and temperature-responsive vegetation boundary and
is therefore potentially valuable as a proxy of climate change in the tropics. However, a review of the current literature about treeline
dynamics in tropical Africa indicates that climate change did not cause rising treelines, due to high human pressure and growing human
population densities. On average the treeline is depressed below its climatic limit by 400 ± 300 meter, but regional differences are high
and there are still many uncertainties. A multidisciplinary study of treeline dynamics is conducted in the north Ethiopian highlands. The
Erica arborea L. treeline is studied over a century, using satellite imagery, aerial photographs, repeat photography and
dendroclimatology. Repeat photography is proven a unique tool for the identification of treeline dynamics on the long-term. Results in
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the Simen Mts. indicate a treeline rise of more than 100 meters since the early 20 century. In contrast, historical satellite and aerial
imagery indicate that there has been strong deforestation since the last 30 years and a significant (p<0.05) but small rise of the treeline
elevation of 11 ± 4 vertical meters in Lib Amba Mt. Dendroclimatological results indicate a weak but significant (p<0.05) correlation
between tree ring width and interannual precipitation patterns. However, since treelines in the African tropical mountains are strongly
disturbed by human and livestock pressure, they cannot directly be used as a proxy for climate change.
Interactions of climate and regional landscape physiography on high elevation forest growth
Kathy Kelsey, Nichole N Barger and Jason Caufield Neff
Forests of the western United States are in a period of rapid change, due in part to climate driven changes in life history processes of
trees such as growth, establishment, and mortality. These changes in forest condition are of particular concern in the American
Southwest where climate conditions are projected to become increasingly hot and dry throughout the next century. While lower
elevation trees of the American Southwest are already experiencing decreased radial growth in response to moisture stress, the
response of high elevation trees to future climate is highly uncertain. Here we use dendro-climatological techniques to explore the
climate-mediated changes in radial tree growth over time in the high elevation forests of southwestern Colorado by sampling 450
Engelmann Spruce and 350 Subalpine Fir from 22 sites across varying aspect, elevation, slope and soil type. Our results indicate
variable and frequently opposing growth responses of individuals of the same species to climate variables; 52% of Engelmann Spruce
sampled (233 individuals) exhibited positive growth responses to warm summer monthly mean temperatures with the remaining 48%
exhibiting negative growth response to warm summer temperatures. We found similarly opposing results for growth response to
monthly precipitation and vapor pressure deficit. In this presentation we explore the physiological factors responsible for variable
climate-growth relationships within these species. Our results suggest a complex response of high elevation forest growth to climate
change, and indicate that efforts to constrain future growth in this region will be contingent on both climatic and local physiographic
factors.
Neighborhood functions alter unbalanced facilitation on a stress gradient in an alpine treeline simulation
George P Malanson and Lynn M Resler
The stress-gradient hypothesis states that individual and species competitive and facilitative effects change in relative importance or
intensity along environmental gradients of stress. The importance of the number of facilitators in the neighborhood of a potential
beneficiary has not been explored. Evenly distributed and stress-correlated facilitation and the increase in the intensity of facilitation
with neighbors as linear, logarithmic, and unimodal functions is simulated for two species such as Pinus albicaulis and Abies lasiocarpa.
The mutualism is unbalanced in that the establishment of one species is enhanced by neighbors more than the other. Compared to no
facilitation or evenly distributed facilitation, the stress gradient produces more edges in the spatially advancing population, more overall
intensity of facilitation, and more individuals further advanced into the area of higher stress; the more enhanced species has increased
population relative to the other – to the point where they are equal. Among three neighborhood functions, little difference exists in
outcomes between the linear and logarithmic functions, but the unimodal function, which shifts peak facilitation intensity to fewer
neighbors, increases the above state variables more than the differences between the even and stress gradient facilitation scenarios.
The unbalanced mutualism may be important at treeline ecotones where the spatial pattern becomes central to facilitation.
Recruitment Patterns and Mature-Tree Growth Response of High-Elevation Pines to Climatic Variability, 1883-2013, Western
Great Basin, USA
Connie Millar, Robert D Westfall and Diane Delany
We monitored recruitment (trees less than 131 years old in 2013) of subalpine Pinus flexilis(PiFl) and P. longaeva (PiLo) along
ecotones at upper, mid, and lower treelines in 7 western Great Basin mountain ranges. Recruitment is greatest near and above current
treeline, but only in scattered, highly localized locations, and predominantly in PiFl , which is leapfrogging 300 m above PiLo.
Recruitment occurred consistently throughout middle and low elevations. At middle elevations, recruitment is extending beyond forest
th
borders into sage meadows; at low elevations, recruitment is extending below the 20 century lower treeline in north-aspect, narrow
ravines. Recruitment for both species was episodic, with a dominant pulse in the interval 1970-2000. This period is associated with wet
autumns and warm growing-season minimum temperatures. Spectral analyses of limber pine recruitment birth year densities resolved
strong primary peaks at 5 years. These peaks occurred at all elevations, but were strongest for high-elevation transects and weakest
for low elevations. Radial growth from four limber pine chronologies (analyzed for the years 1883 to 2013) showed greatest growth
during the same period as the recruitment pulse, with significant declines in growth since 1990 at all sites.
Effect of soil quality on determining the timberline at the Pico de Orizaba volcano
Paola Molina Sevilla, Rafael Navarro-Gonzalez, Christopher P McKay, Pablo Martinez-Sosa and Laura Esquivel-Hernandez
The inactive volcano Pico de Orizaba, located in the state of Veracruz, Mexico, has the highest treeline in the world at 4100 m above
sea level, with the predominant tree species Pinus hartweggii. At this altitude trees are exposed to extreme conditions such as: low
temperature (5°C), low humidity (<1%), UV radiation and a thinner atmosphere, among others factors. The study of soil factors is of
paramount importance to understand the response of treeline to global warming. We have studied the physical and bioclimatic
properties of the soils along altitudinal gradient (3500 a 4400 m) on the South face of Pico de Orizaba: organic matter, real and
apparent density, texture and total amount of Va and Mo. Soil samples at treeline were also used to prepare thin sections to study the
soil micromorphology. There is a disruption of values along the altitudinal gradient at treeline, between 4000 and 4100. The C/N ratio of
soils below the treeline is typical of forest regions; however above 4100 m the value decreases to less than 1%. Also the quantity of
interchangable cations is below 1cmol/kg above treeline. Analysis of thin soil sections show little weathering and compaction on regions
above the treeline. We suggest that at least nine factors intervene in tree growth on the transition zone: soil temperature, organic
matter, interchangable cations, clay content, compaction, porosity, C/N ratio, biological activity and soil structure. At the moment we
cannot yet discern if some of them is preponderant as all of them are interlinked.
Neighborhood Climate Change Effects on Treeline Communty Dynamics in Basin and Range Mountains
Brian Smithers, Connie Millar, and Malcolm North
Treeline advance is an expected sensitive indicator of climate change effects on species distributions. However, little evidence of
treeline advance has been shown due to past disturbance or geomorphological limitations. The Basin and Range Mountains of Nevada
and eastern California have seen minimal human impact and have been free of major glaciation, making these mountains an ideal
location to test for climate change impacts on treeline. Great Basin treelines are dominated by bristlecone pine but recent observations
show that usually downslope-growing limber pine appears to be pushing treeline upslope. In this study, we used modified belt transects
at above and below adult treeline and at stand mid-elevation to compare species regeneration with adult, cone-bearing tree basal area.
Our results show that limber pine regeneration surpasses bristlecone pine regeneration at treeline in terms of raw numbers of
individuals. When adult basal area is taken into consideration, it appears that the very few adult limber pines have far more
regeneration success at treeline than the bristlecone pine adults. This may have long-term ramifications on community composition of
bristlecone pine forests, as these long-lived individuals largely exclude one another once established. Limber pine appears to be far
better adapted to take advantage of rapid climate change. Even if bristlecone pine is ultimately better adapted to treeline in the longterm and this “changing of the guard” at treeline is temporary, due to their long lifespan, this effect could last thousands of years.
Evidence That Drought-Induced Stomatal Closure Is Not an Important Constraint on White Spruce Performance Near the
Arctic Treeline in Alaska
Paddy Sullivan, Annalis Brownlee, Sarah Ellison and Bjartmar Sveinbjornsson
Tree cores collected from trees growing at high latitudes have long been used to reconstruct past climates, because of close positive
correlations between temperature and tree growth. However, in recent decades and at many sites, these relationships have
deteriorated and have even become negative in some instances. The observation of declining tree growth in response to rising
temperature has prompted many investigators to suggest that high latitude trees may be increasingly exhibiting drought-induced
stomatal closure. In the Brooks Range of northern Alaska, the observation of low and declining growth of white spruce is more
prevalent in the central and eastern parts of the range, where precipitation is lower, providing superficial support for the drought stress
hypothesis. In this study, we investigated the occurrence of white spruce drought-induced stomatal closure in four watersheds along a
west to east gradient near the Arctic treeline in the Brooks Range. We obtained a historical perspective on tree growth and water
relations by collecting increment cores for analysis of ring widths and carbon isotopes in tree-ring alpha-cellulose. Meanwhile, we made
detailed assessments of contemporary water relations at the scales of the whole canopy and the needle. All of our data indicate that
drought-induced stomatal closure is probably not responsible for low and declining growth in the central and eastern Brooks Range.
Carbon isotope discrimination has generally increased over the past century and our calculations indicate that needle inter-cellular CO2
concentration is much greater now than it was in the early 1900’s. Measurements of needle gas exchange are consistent with the tree
core record, in the sense that instances of low photosynthesis at our sites are not coincident with similarly low stomatal conductance
and low inter-cellular CO2 concentration. Finally, hourly measurements of xylem sap flow indicate that trees at our study sites are able
to maintain near peak canopy transpiration under the highest atmospheric vapor pressure deficits observed (>3.0 kPa). Thus, our treering data provide further evidence of what has become known as the “divergence problem” in northern forests, but our physiological
measurements suggest that drought-induced stomatal closure may not be the cause.
Morphological and Physiological Compensation Promote Climate-Induced Invasions Above and Below Treeline
Daniel Edward Winkler, Travis E Huxman and Gaku Kudo
Elucidating the mechanisms underlying invasive species success is a challenge in ecology. Treeline ecotones are eminently suited to
address this challenge given their sensitivity to climate change and the different abiotic filters in place over short distances. The
invasive dwarf bamboo Sasa kurilensis has had pronounced effects on Japanese alpine plant communities, including the loss of over
1/3 of native species in some areas. The drivers of S. kurilensis invasions remain unresolved. We evaluated S. kurilensis stands along
elevation and moisture gradients in Daisetsuzan National Park (Hokkaido, Japan) to identify strategy shifts that might facilitate
invasions. We anticipated morphological responses to be correlated with invasion above treeline, while physiological processes to be
more coordinated below treeline, reflecting different ecological filters in place within each community. We compared growth patterns
and plant water status in the native (i.e., montane forests) and invasive (i.e., subalpine and alpine meadows) ranges of S. kurilensis.
Dwarf bamboo at native lower elevations were taller than those at newly-invaded upper limits, indicating light limitation and investment
in culm elongation. Culms in the native range grew faster than those at higher elevations. In contrast, culm density increased and plants
allocated more to photosynthetic structures in invaded areas without overstory. Plants tended to invade drier soils but showed
increased water stress, likely compensating by producing more photosynthetic structures to promote carbon gain. Overall, our results
reveal dwarf bamboo exhibits both morphological and physiological variation across treeline ecotones. This appears to enable it to
successfully invade subalpine and alpine communities while responding to a new climate. This pattern of variation coupled with
changing soil dynamics as a result of earlier snowmelt will likely continue to promote the invasion of S. kurilensis into these systems.
Linking resource allocation strategies and physiological responses to environmental variation will produce a mechanistically-based
predictive framework vital to helping federal agencies apply limited funds to optimally conserve and manage sensitive lands.
Session 2: Forests Under a Changing Climate: Uncertainties, Carbon Management, and Adaptation
TALKS
Toward optimizing the delivery and use of climate science for natural resource management: lessonslearned from recent
adaptation efforts in the southwestern U.S.
Carolyn Enquist
Within the past decade, a wealth of federal, state, and NGO-driven initiatives has emerged across managed landscapes in the United
States with the goal of facilitating a coordinated response to rapidly changing climate and environmental conditions. In addition to
acquisition and translation of the latest climate science, climate vulnerability assessment and scenario planning at multiple spatial and
temporal scales are typically major components of such broad adaptation efforts. Numerous approaches for conducting this work have
emerged in recent years and have culminated in general guidance and trainings for resource professionals that are specifically
designed to help practitioners face the challenges of climate change. In particular, early engagement of stakeholders across multiple
jurisdictions is particularly critical to cultivate buy-in and other enabling conditions for moving the science to on-the-ground action. I
report on a suite of adaptation efforts in the southwestern US and interior Rockies, highlighting processes used, actions taken, lessons
learned, and recommended next steps to facilitate achieving desired management outcomes. This includes a discussion of current
efforts to optimize funding for actionable climate science, formalize science-management collaborations, and facilitate new investments
in approaches for strategic climate-informed monitoring and evaluation.
Adapting Natural Resource Management to Climate Change: The Blue Mountains and Northern Rockies Adaptation
Partnerships
Jessica Halofsky and David L Peterson
Concrete ways to adapt to climate change are needed to help natural resource managers take the first steps to incorporate climate
change into management and take advantage of opportunities to balance the negative effects of climate change. We recently initiated
two science-management climate change adaptation partnerships, one with three national forests and other key stakeholders in the
Blue Mountains region of northeastern Oregon, and the other with 16 national forests, three national parks and other stakeholders in
the northern Rockies region. Goals of both partnerships were to: (1) synthesize published information and data to assess the exposure,
sensitivity, and adaptive capacity of key resource areas, including water use, infrastructure, fisheries, and vegetation and disturbance;
(2) develop science-based adaptation strategies and tactics that will help to mitigate the negative effects of climate change and assist
the transition of biological systems and management to a warmer climate; (3) ensure adaptation strategies and tactics are incorporated
into relevant planning documents; and (4) foster an enduring partnership to facilitate ongoing dialogue and activities related to climate
change in the partnerships regions. After an initial vulnerability assessment by agency and university scientists and local resource
specialists, adaptation strategies and tactics were developed in a series of scientist-manager workshops. The final vulnerability
assessments and adaptation actions are incorporated in technical reports. The partnerships produced concrete adaptation options for
national forest and other natural resource managers and illustrated the utility of place-based vulnerability assessments and scientistmanager workshops in adapting to climate change.
Simulating Climate, Fire, and Management Influences on Forest Carbon Dynamics in Single- and Multi-Species Forests of the
Southwestern and Southeastern US
Matthew D Hurteau
The interaction of climate, disturbance, and management on forest structure and composition can alter carbon dynamics.
Understanding how these factors influence forest carbon dynamics individually and in combination is necessary for making forest
projections under altered climatic conditions. Model and emission scenario uncertainty in climate projections presents one challenge.
When simulating disturbance, such as fire, projected climate influences both fire behavior and post-wildfire regeneration. The outcome
of management actions implemented to alter forest conditions can be influenced by both climate and disturbance. Simulation results in
both single- and multi-species forests occupying different future climate space indicate the importance of between climate model
variation and variation between emission scenarios. The variation in projected biomass as a function of climate model input is as much
as 40%. Response to emission scenario varies as a function of climate space, with increased late-century divergence in net ecosystem
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exchange (NEE) and biomass. When fire is simulated, climate model influence on biomass ranged from 0-27 Mg ha , while the effect
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on NEE ranged from -279 to 238 g m . Management implemented to reduce fire risk or provide wildlife habitat influences near- and
long-term carbon dynamics as a function of projected climate, with the difference between no management and management for fire
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risk yielding a range in biomass of 0.6 to 10.78 Mg ha and relatively little change in NEE (-8 to 21 g m ). Given the range of results,
including a suite of models and emission scenarios allow for bracketing the range of future forest conditions. However, the mismatch in
scales between climate projections and the microclimatic influences on regeneration and the influence of projected climate on wildfire
frequency and type add sources of uncertainty to these projections that require additional investigation.
Assessing Land Management Change Effects on Forest Carbon and Emissions Under Changing Climate
Beverly Elizabeth Law
There has been limited focus on fine-scale land management change effects on forest carbon under future environmental conditions
(climate, nitrogen deposition, increased atmospheric CO2). Forest management decisions are often made at the landscape to regional
levels before analyses have been conducted to determine the potential outcomes and effectiveness of such actions. Scientists need to
evaluate plausible land management actions in a timely manner to help shape policy and strategic land management.
Issues of interest include species-level adaptation to climate, resilience and vulnerability to mortality within forested landscapes and
regions. Efforts are underway to improve land system model simulation of future mortality related to climate, and to develop and
evaluate plausible land management options that could help mitigate or avoid future die-offs. Vulnerability to drought-related mortality
varies among species and with tree size or age. Predictors of species ability to survive in specific environments are still not resolved. A
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challenge is limited observations for fine-scale (e.g. 4 km ) modeling, particularly physiological parameters. Uncertainties are primarily
associated with future land management and policy decisions. They include the interface with economic factors and with other
ecosystem services (biodiversity, water availability, wildlife habitat). The outcomes of future management scenarios should be
compared with business-as-usual management under the same environmental conditions to determine the effects of management
changes on forest carbon and net emissions to the atmosphere. For example, in the western U.S., land system modeling and life cycle
assessment of several management options to reduce impacts of fire reduced long-term forest carbon gain and increased carbon
emissions compared with business-as-usual management under future environmental conditions. The enhanced net carbon uptake with
climate and reduced fire emissions after thinning did not compensate for the increased wood removals over 90 years, leading to
reduced net biome production. Analysis of land management change scenarios at fine scales is needed, and should consider other
ecological values in addition to carbon.
Designing Forest Adaptation Experiments through Manager-Scientist Partnerships
Linda Marie Nagel, Christopher Swanston and Maria Janowiak
Three common forest adaptation options discussed in the context of an uncertain future climate are: creating resistance, promoting
resilience, and enabling forests to respond to change. Though there is consensus on the broad management goals addressed by each
of these options, translating these concepts into management plans specific for individual forest types that vary in structure,
composition, and function remains a challenge. We will describe a decision-making framework that we employed within a managerscientist partnership to develop a suite of adaptation treatments for two contrasting forest types as part of a long-term forest
management experiment. The first, in northern Minnesota, is a red pine-dominated forest with components of white pine, aspen, paper
birch, and northern red oak, with a hazel understory. The second, in southwest Colorado, is a warm-dry mixed conifer forest dominated
by ponderosa pine, white fir, and Douglas-fir, with scattered aspen and an understory of Gambel oak. The current conditions at both
sites are characterized by overstocking with moderate-to-high fuel loading, vulnerability to numerous forest health threats, and are
generally uncharacteristic of historic structure and composition. The desired future condition articulated by managers for each site
included elements of historic structure and natural range of variability, but were greatly tempered by known vulnerabilities and projected
changes to climate and disturbance patterns. The resultant range of treatments we developed are distinct for each forest type, and
address a wide range of management objectives.
“Actionable” Climate Scenarios for Natural Resource Managers in Southwestern Colorado
Imtiaz Rangwala, Renee Rondeau and Carina Wyborn
Locally relevant projections of climate change provide critical insights for natural resource managers seeking to adapt their
management activities to climate change. To provide such information, we developed narrative scenarios of future climate change and
its impacts on different ecosystems in southwestern Colorado. This multi-institution and trans-disciplinary project seeks to provide
useful and useable knowledge to facilitate climate change adaptation in the context of uncertainty. The narratives are intended to
provide detailed insights into the range of changes that natural resource managers may face in the future. These scenarios were
developed in an iterative process through interactions between ecologists, social and climate scientists. In our scenario development
process, climate uncertainty is acknowledged by having multiple scenarios, where each scenario is regarded as a storyline with equal
probability as another scenario. Rather than a qualitative narration of the general direction of change and range in responses, we
quantified changes in several decision relevant climate and ecological responses based on our best available understanding and
provided a tight storyline for each scenario to facilitate (a) a more augmented use of scientific information in a decision-making process,
(b) differential responses from stakeholders across the different scenarios, and (c) identification of strategies that could work across
these multiple scenarios. This presentation will discuss the process of selecting the scenarios, quantifying climate and ecological
responses, and the criteria for building the narrative for each scenario. We will also cover the process by which these scenarios get
used, and how the user feedbacks are integrated in further developing the tools and processes.
Adaptation Forestry in Minnesota's Northwoods
Meredith Cornett, Mark White, Julie Etterson, Laura Kavajecz, Jordan Mead, Stephen Handler, Christopher Swanston and
Kimberly Hall
Forest restoration and management goals are shifting in northern Minnesota in light of new information on climate trends. Adaptation
forestry encompasses a combination of practices designed to favor native populations and species likely to persist under warmer, drier
conditions. The overarching project goal is to increase the adaptive capacity of northern forests such that they continue to sustain a
variety of services, including carbon sequestration, fiber production, watershed protection, and wildlife habitat. We are currently testing
the feasibility and efficacy of adaptation forestry in the northern Great Lakes region in three common forest types: Boreal-Mixed, Pine,
and Hardwoods. 12 sites (2,000 acres total) recently subjected to a range of structural treatments (gap creation, shelterwood, and
clear-cut with reserves) were coupled with “adaptation plantings” of species that are likely to thrive under changed climate conditions
(e.g., red oak, bur oak, white pine). Seedlings, ~110,000 total, originated from two source locations, one that reflects current adaptation
to the climate of northern Minnesota and another from a more southern source in central Minnesota. To date, we have assessed results
from two growing seasons by tracking survival, growth and phenological characteristics of planted seedlings. This project is a first step
in determining whether adaptation management can be used as a tool to help northern forests transition to an uncertain future.
Cooperation with state, federal, and academic partners may ultimately influence the adaptive capacity across millions of acres in the
Great Lakes region.
Reducing Uncertainty and Increasing Consistency: Recent Technical Improvements to the 2015 United States Forest Carbon
Inventory
Christopher W Woodall, Grant M Domke and John Coulston
A national system of field inventory plots is the primary data source for the annual assessment of US forest carbon (C) stocks and
stock-change to meet reporting requirements under the United Nations Framework Convention on Climate Change (UNFCCC). The
inventory data and their role in national carbon reporting continue to evolve. The Forest Inventory and Analysis (FIA) program of the
USDA Forest Service is charged with conducting the field inventory of US forest C. The FIA program employs remotely sensed imagery
to define forest and nonforest plots which are systematically distributed approximately every 2,428 ha across the conterminous US.
More than 125,000 plots in the current field inventory have at least one forested condition where field crews measure tree- and sitelevel attributes (e.g., diameter and tree height) at regular temporal intervals. A subset of forested plots is measured for additional
variables related to forest non-tree C pools (e.g., downed woody materials, understory vegetation, and soils). The FIA program does not
directly measure forest C stocks. Instead, a combination of empirically derived C estimates (e.g., standing live and dead trees) and
models (e.g., understory C stocks related to stand age and forest type) are used to estimate forest C stocks. A series of recent
refinements in FIA estimation procedures have sought to reduce the uncertainty associated with the national C inventory by: 1) refining
forest floor C estimates with in situ data, 2) updating the live belowground and understory C pools modeling approaches, 3) refining
objective delineations between woodland and forest land uses, and 4) revising managed land delineations. The results of these studies
in the context of forest C accounting and future refinements are discussed in the context of UNFCCC reporting.
POSTERS
Assessing Soil Organic Carbon Stocks in Fire-Affected Pinus palustris Forests
John R Butnor, Kurt H Johnsen, Jason A Jackson, Peter H Anderson, Lisa J Samuelson and Klaus Lorenz
This study aimed to quantify the vertical distribution of soil organic carbon (SOC) and its biochemically resistant fraction (SOCR; defined
as residual SOC following H2O2 treatment and dilute HNO3 digestion) in managed longleaf pine (LLP) stands located at Fort Benning,
Georgia, USA (32.38 N., 84.88 W.). Although it is unclear how to increase SOCR via land management, it is a relatively stable carbon
(C) pool that is important for terrestrial C sequestration. SOC concentration declines with soil depth on upland soils without a spodic
horizon; however, the portion that is SOCR and the residence time of this fraction on LLP stands is unknown. Soils were collected by
depth at five sites with common land use history, present use for active military training and a three-year prescribed fire return
cycle. Soils were treated with H2O2 and dilute HNO3 to isolate SOCR. In the upper 1-m of soil SOC stocks averaged 72.1 ± 6.6 Mg C ha
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and SOCR averaged 25.8 ± 3.2 Mg C ha . Depending on the site, the ratio of SOCR:SOC ranged from 0.25 to 0.50 in the upper 1-m of
soil. On clayey soils the ratio of SOCR:SOC increased with soil depth. One site containing 33% clay at 50 to 100 cm depth had a
SOCR:SOC ratio of 0.68. The radiocarbon age of SOCR increased with soil depth, ranging from approximately 2,000 years before
present (YBP) at 0 to 10 cm to over 5,500 YBP at 50 to 100 cm depth. Across all sites, SOCR makes up a considerable portion of SOC.
What isn’t clear is the proportion of SOCR that is of pyrogenic origin (black carbon), versus SOCR that is stabilized by association with
the mineral phase. Ongoing analysis with 13C nuclear magnetic resonance spectroscopy will provide data on the degree of aromaticity
of the SOCR and some indication of the nature of its biochemical stability.
Enhancing Tools and Geospatial Data to Support Operational Forest Management and Regional Forest Planning in the Face of
Climate Change
Michael J Falkowski, Patrick Fekety, Andrew T Hudak, Nilam Kayastha and Linda Marie Nagel
A detailed understanding of how forest composition, structure, and function will be impacted by projected climate change and related
adaptive forest management activities are particularly lacking at local scales, where on-the-ground management activities are
implemented. Climate sensitive forest dynamics models may prove to be effective tools for developing a comprehensive understanding.
However, to be applicable to both regional forest planning and operational forest management, modeling approaches must be capable
of simulating forest dynamics across large spatial extents (required for regional planning) while maintaining a high-level of spatial detail
(required for operational management). LiDAR remote sensing has shown great utility for operational forest inventory and management,
including forest dynamics modeling, albeit across relatively small spatial extents. We present a remote sensing driven approach to
spatially initialize a climate-sensitive forest dynamics model (LANDIS-II) in the Pacific Northwest of the US via an integration of airborne
LiDAR data with satellite remote sensing data. The system provides detailed forest inventory information - at the landscape level - that
is subsequently employed to demonstrate how such models can be used to 1) investigate the potential impacts of climate change on
future forest composition and structure, and 2) assess how various forest management practices may either enhance or degrade forest
resilience to changing climate and disturbance regimes.
PDF Weaving - Linking Inventory Data and Monte Carlo Uncertainty Analysis in the Study of how Disturbance Affects Forest
Carbon Storage
Sean P Healey, Paul Patterson and Chris Garrard
Altered disturbance regimes are likely a primary mechanism by which a changing climate will affect storage of carbon in forested
ecosystems. Accordingly, the National Forest System (NFS) has been mandated to assess the role of disturbance (harvests, fires,
insects, etc.) on carbon storage in each of its planning units. We have developed a process which combines 1990-era maps of forest
structure and composition with high-quality maps of subsequent disturbance type and magnitude to track the impact of disturbance on
carbon storage. This process, called the Forest Carbon Management Framework (ForCaMF), uses the maps to apply empirically
calibrated carbon dynamics built into a widely used management tool, the Forest Vegetation Simulator (FVS).
While ForCaMF offers locally specific insights into the effect of historical or hypothetical disturbance trends on carbon storage, its
dependence upon the interaction of several maps and a carbon model poses a complex challenge in terms of tracking uncertainty.
Monte Carlo analysis is an attractive option for tracking the combined effects of error in several constituent inputs as they impact overall
uncertainty. Monte Carlo methods iteratively simulate alternative values for each input and quantify how much outputs vary as a result.
Variation of each input is controlled by a Probability Density Function (PDF). We introduce a technique called “PDF Weaving,” which
constructs PDFs that ensure that simulated uncertainty precisely aligns with uncertainty estimates that can be derived from inventory
data. This hard link with inventory data (derived in this case from FIA – the US Forest Service Forest Inventory and Analysis program)
both provides empirical calibration and establishes consistency with other types of assessments (e.g., habitat and water) for which NFS
depends upon FIA data. Results from the NFS Northern Region will be used to illustrate PDF weaving and insights gained from
ForCaMF about the role of disturbance in carbon storage.
An inventory-based approach for estimating the managed China’s forest biomass carbon stock
Mei Huang, Guirui Yu, Xiliu Yue and Junbang Wang
China’s forests cover a large area and have the characteristics of young age thus have the potential for a major role in mitigate the rate
of global climate change. On the basis of forest inventory data and spatial distribution of forest stand age and forest type, we developed
an approach for estimating yearly China’s forest biomass carbon stocks change. Using this approach, we estimated the changes of
forest carbon stock due to management practice and forest age structure change, respectively, and predicted China’s future carbon
potential based on national forest expansion plan. We also discussed sustainable harvesting intensity for the expanded forest of 2020.
The spatial pattern of forest biomass carbon density in 2001 showed high in southwestern and northeastern areas, and low in the other
regions, meanwhile the high C sinks appeared in the southwestern and northeastern young-aged forests and low in the southwestern
and northeastern old-aged forests. The total forest biomass C stock of China increased from 6.06 Pg C in 2001 to 7.88 Pg C in 2013,
giving a total increase of 1.82 Pg C, in which 0.45 Pg C is caused by forest expansion. The average C sink during 2002-2013 was
151.83 Tg C, in which 75.5% is the results of forest growth and 24.5% is caused by forest expansion. With the assumption of China’s
forest area will expand by 40 million hectares from 2006 to 2020, the forest C stock in 2020 is predicted as 9.04 Pg C. Harvesting
intensity experiments conducted on the expanded forest of 2020 shown higher harvesting level will lead to decline in forest biomass in
long term. The harvesting level of 2% is an optimal harvesting intensity for sustainable development of China’s forest resources.
Simulating Pacific Northwest Forest Response to Climate Change: How We Made Model Results Useful for Vulnerability
Assessments
John B Kim, Becky K Kerns, and Jessica Halofsky
GCM-based climate projections and downscaled climate data proliferate, and there are many climate-aware vegetation models in use
by researchers. Yet application of fine-scale DGVM based simulation output in national forest vulnerability assessments is not common,
because there are technical, administrative and social barriers for their use by managers and policy makers. As part of a sciencemanagement climate change adaptation partnership, we performed simulations of vegetation response to climate change for four
national forests in the Blue Mountains of Oregon using the MC2 dynamic global vegetation model (DGVM) for use in vulnerability
assessments. Our simulation results under business-as-usual scenarios suggest a starkly different future forest conditions for three out
of the four national forests in the study area, making their adoption by forest managers a potential challenge. However, using DGVM
output to structure discussion of potential vegetation changes provides a suitable framework to discuss the dynamic nature of
vegetation change compared to using more commonly available model output (e.g. species distribution models). From the onset, we
planned and coordinated our work with national forest managers to maximize the utility and the consideration of the simulation results in
planning. Key lessons from this collaboration were: (1) structured and strategic selection of a small number climate change scenarios
that capture the range of variability in future conditions simplified results; (2) collecting and integrating data from managers for use in
simulations increased support and interest in applying output; (3) a structured, regionally focused, and hierarchical calibration of the
DGVM produced well-validated results; (4) simple approaches to quantifying uncertainty in simulation results facilitated communication;
and (5) interpretation of model results in a holistic context in relation to multiple lines of evidence produced balanced guidance. This
latest point demonstrates the importance of using model out as a forum for discussion along with other information, rather than using
model output in an inappropriately predictive sense. These lessons are being applied currently to other national forests in the Pacific
Northwest to contribute in vulnerability assessments.
Simulating Carbon Dynamics and Species Composition Under Projected Changes in Climate in the Puget Sound, Washington,
USA
Danelle Laflower, and Matthew D Hurteau
Changing climate has the potential to directly and indirectly alter forest carbon dynamics and species composition, particularly in
temperature or precipitation limited systems. In light-limited systems, species-specific response to changing climate could result in an
indirect effect of climate through altered competitive interactions. Joint Base Lewis-McChord, in Washington, contains one of the largest
intact forested areas in the Puget Sound. Management priorities include development of late-successional forests and conservation.
We sought to quantify how projected changes in climate would affect species diversity and carbon (C) sequestration given management
priorities. We used Landis-II to simulate forest dynamics over 100 years using current climate and projected climate under two emission
scenarios. Preliminary analyses indicate a decrease in soil C, relative to current climate, beginning mid-century for both emission
scenarios. Under the low emission scenario, the decrease is compensated by increased aboveground C, while the high scenario
experiences a decline in aboveground C. Total ecosystem C was consistent between baseline and low emission climate throughout the
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simulation. By late-century, the high scenario had an average decrease of 10 Mg C ha . Douglas-fir (DF) accounts for the largest
fraction of aboveground biomass (AGB) in the study area. Interestingly, DF AGB was fairly consistent between climate scenarios
through mid-century, but diverged during late-century, with the high scenario having the greatest amount of DF AGB (mean 368 Mg ha
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) and current climate having the lowest (mean 341 Mg ha ). We found the inverse relationship when examining all other species.
Given the uncertainty associated with climate projections, future simulations will include a larger suite of climate projections and
address the secondary effects of climate change (e.g. increased wildfire, disease or insect outbreaks) that can impact productivity.
Investigating Appropriate Sampling Design for Estimating Above-Ground Biomass in Bruneian Lowland Mixed Dipterocarp
Forest
Dongho Lee, Sohye Lee, Kamariah Abu Salim, Hyeon Min Yun, Saerom Han, Woo-Kyun Lee, Stuart J Davies and Yowhan Son
Mixed tropical forest structure is highly heterogeneous unlike plantation or mixed temperate forest structure, and therefore, different
sampling approaches are required. However, the appropriate sampling design for estimating the above-ground biomass (AGB) in
Bruneian lowland mixed dipterocarp forest (MDF) has not yet been fully clarified. The aim of this study was to provide supportive
information in sampling design for Bruneian forest carbon inventory. The study site was located at Kuala Belalong lowland MDF, which
is part of the Ulu Tembulong National Park, Brunei Darussalam. Six 60 m × 60 m quadrats were established, separated by a distance of
approximately 100 m and each was subdivided into quadrats of 10 m × 10 m, at an elevation between 200 and 300 m above sea level.
At each plot all free-standing trees with diameter at breast height (dbh) ≥ 1 cm were measured. The AGB for all trees with dbh ≥ 10 cm
was estimated by allometric models. In order to analyze changes in the diameter-dependent parameters used for estimating the AGB,
different quadrat areas, ranging from 10 m × 10 m to 60 m × 60 m, were used across the study area, starting at the South-West end
and moving towards the North-East end. The derived result was as follows: (a) Big trees (dbh ≥ 70 cm) with sparse distribution have
remarkable contribution to the total AGB in Bruneian lowland MDF, and therefore, special consideration is required when estimating the
AGB of big trees. Stem number of trees with dbh ≥ 70 cm comprised only 2.7% of all trees with dbh ≥ 10 cm, but 38.5% of the total
AGB. (b) For estimating the AGB of big trees at the given acceptable limit of precision (p), it is more efficient to use large quadrats than
to use small quadrats, because the total sampling area decreases with the former. Our result showed that 239 20 m × 20 m quadrats
(9.6 ha in total) were required, while 15 60 m × 60 m quadrats (5.4 ha in total) were required when estimating the AGB of the trees with
dbh ≥ 70 cm at 10% p. (c) In order to decrease the measurement time, it is necessary to use nested quadrats containing smaller subquadrats. Also, it was found that when 15 60 m × 60 m quadrats for trees with dbh ≥ 70 cm, and 20 m × 20 m sub-quadrats for trees
with dbh of 10.0-19.9 cm were used, AGB could be estimated below 10% p for both dbh classes.
Modeling Forest Composition and Carbon Dynamics Under Projected Climate-Fire Interactions in the Sierra Nevada,
California
Shuang Liang, Matthew D Hurteau and Anthony Leroy Westerling
The Sierra Nevada Mountains are occupied by a diversity of forest types that sort by elevation. The interaction of changing climate and
altered disturbance regimes (e.g. fire) has the potential to drive changes in forest distribution as a function of species-specific response.
Quantifying the effects of these drivers on species distributions and productivity under future climate-fire interactions is necessary for
informing mitigation and adaptation efforts. In this study, we assimilated forest inventory and soil survey data and species life history
traits into a landscape model, LANDIS-II, to quantify the response of forest dynamics to the interaction of climate change and large
wildfire frequency in the Sierra Nevada. We ran 100-year simulations forced with historical climate and climate projections from three
models (GFDL, CNRM and CCSM3) driven by the A2 emission scenario. We found that non-growing season NPP is greatly enhanced
by 15%-150%, depending on the specific climate projection. The greatest increase occurs in subalpine forests. Species-specific
response varied as a function of life history characteristics. The distribution of drought and fire-tolerant species, such as ponderosa
pine, expanded by 7.3-9.6% from initial conditions, while drought and fire-intolerant species, such as white fir, showed little change in
the absence of fire. Changes in wildfire size and frequency influence species distributions by altering the successional stage of burned
patches. The range of responses to different climate models demonstrates the sensitivity of these forests to climate variability. The
scale of climate projections relative to the scale of forest simulations presents a source of uncertainty, particularly at the ecotone
between forest types and for identifying topographically mediated climate refugia. Improving simulations will likely require higher
resolution climate projections.
Biomass of Secondary Evergreen and Deciduous Broadleaved Mixed Forest in Plateautype Karst Terrain of Guizhou Province, SW China
Libin Liu
Using allometric functions, harvest and soil column methods, we investigated the biomass of a secondary evergreen and deciduous
broadleaved mixed forest in Tianlongshan permanent monitoring plot (a horizontally-projected area of 2 hectares) of Puding Karst
Ecosystem Research Station, Guizhou Province, southwestern China. Results showed that the total biomass of the forest is 165.4
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Mg·hm . The aboveground biomass and root biomass are 137.7 Mg·hm and 27.7 Mg·hm , respectively. Among the aboveground
biomass, the tree layer accounts for 97.76%, which is obviously greater than the shrub layer and herb layer. Larger trees (the diameter
at breast height, DBH is between 5 cm and 20 cm) occupies 76.85% of the aboveground biomass, especially the five dominant
species(Lithocarpus confinis, Platycarya longipes, Itea yunnanensis, Machilus cavaleriei and Carpinus pubescens). Shrubs and lianas
(DBH = 1 cm) account for more than 30% of total shrub and liana biomass, although their individuals are less than 2% of total shrub
individuals and 1% of total liana individuals, respectively. The root biomass differs in root diameters, i.e. coarse root > medium root >
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fine root. Root biomass decreases with the increase of soil depth. Within soil depth of 20 cm, the root biomass is 20.1 Mg·hm , which is
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more than 70% of total root biomass. Within soil depth of 50 cm, the root biomass is 26.7 Mg·hm , which is 96.39% of total root
biomass. Compared with non-karst forests in the same climate zone, karst forest has lower biomass and carbon stock, but it further has
greater potential of carbon sink.
Science-based Forest Management in an Era of Climate Change
Christopher Swanston, Maria Janowiak, Leslie Brandt, Patricia Butler, Stephen Handler and Danielle Shannon
Recognizing the need to provide climate adaptation information, training, and tools to forest managers, the Forest Service joined with
partners in 2009 to launch a comprehensive effort called the Climate Change Response Framework (www.forestadaptation.org). The
Framework provides a structured approach to help managers integrate climate considerations into forest management plans and then
implement adaptation actions on the ground. A planning tool, the Adaptation Workbook, is used in conjunction with vulnerability
assessments and a diverse “menu” of adaptation approaches to generate site-specific adaptation actions that meet explicit
management objectives. Additionally, a training course, designed around the Adaptation Workbook, leads management organizations
through this process of designing on-the-ground adaptation tactics for their management projects.
The Framework is now being actively pursued in 20 states in the Northwoods, Central Hardwoods, Central Appalachians, Mid-Atlantic,
and New England. The Framework community includes over 100 science and management groups, dozens of whom have worked
together to complete six ecoregional vulnerability assessments covering nearly 135 million acres. More than 75 forest and urban forest
adaptation strategies and approaches were synthesized from peer-reviewed and gray literature, expert solicitation, and on-the-ground
adaptation projects. These are being linked through the Adaptation Workbook process to on-the-ground adaptation tactics being
planned and employed in more than 50 adaptation “demonstrations”. This presentation will touch on the scientific and professional
basis of the vulnerability assessments, and showcase efforts where adaptation actions are currently being implemented in forests.
Estimates of carbon allocation to ectomycorrhizal fungi in a temperate forest
Shersingh Joseph Tumber-Davila and Andrew Ouimette
Nitrogen (N) limitation restricts net primary productivity both globally and within the northeastern United States; therefore limiting the
amount of carbon stored. Despite the importance of N to carbon (C) storage, we still lack an understanding of how trees compete for N
belowground. In the Northeasters UN, trees associate with two main groups of fungal symbionts which supply the plant nitrogen, either
ectomcorrhizal (ECM) or arbuscular mycorrhizal (AM) fungi. Since ECM creates an extensive hyphal network and has strong enzymatic
capabilities, they are generally favored in forests with low N availabilities; however they have a higher C demand.
Here we attempt to provide a more thorough understanding of whole-plant carbon allocation in temperate forests, by quantifying wood,
foliar, and root NPP, as well as belowground C allocation to ECM fungi. The study was conducted across plots with a range of N
availability and tree species composition within Bartlett Experimental Forest (BEF), NH, a current NEON site.
Ingrowth core-methods utilized in the study indicate there is high soil fungal biomass in N-poor sites than at N-rich sites with the N-poor
sites averaging at 600 grams of fungal carbon per meter squared compared to the N-rich sites having less than 200 grams. Soil, foliar,
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and root N isotopes (δ N) show evidence of enhanced N isotope fractionation and C allocation to mycorrhizal fungi in the N-poor sites.
Results from this study are being used to incorporate C allocation to mycorrhizal fungi into a process-based forest ecosystem.
User-relevant Climate Data for Climate Impact Assessment: The Wisconsin Initiative on Climate Change Impacts Downscaled
Climate Data
Daniel Vimont and David J Lorenz
The Wisconsin Initiative on Climate Change Impacts (WICCI) is Wisconsin’s approach to climate adaptation. WICCI’s mission is to
generate and share information that cam limit vulnerability to climate change in Wisconsin and the Upper Midwest. WICCI is modeled
as a conversation between stakeholders and scientists, which provides an efficient means of both generating knowledge about specific
impacts of climate change, and enabling action toward adaptation. This talk will describe how WICCI has used this framework to
develop user-relevant downscaled climate data for the Eastern United States and Canada that are being used in a variety of ways for
climate impact assessment.
Carbon of Woody Debris in Plateau-type Karst Evergreen and Deciduous Broad-leaved Mixed Forest of Central Guizhou
Province
Yangyang Wu, Jian Ni, Libin Liu and Chunzi Guo
Woody debris (WD) is an essential structural and functional component of forest ecosystems, and plays very significant roles for the
biogeochemical cycling of carbon and nutrients. Coarse woody debris (CWD) is considered to be the major part in forest WD and it is
primarily composed of logs, snags, stumps and large branches, while fine woody debris (FWD) mainly consists of small twigs.
Composition, spatial distribution and carbon storage of WD have been studied in plateau-type karst evergreen and deciduous broadleaved mixed forest in Tianlong Mountain of central Guizhou Province. Results showed that the carbon storage of WD in karst forests
was less than non-karst forests. The major components of WD were fallen trees and snags with 10-20 cm in diameter. Fallen trees and
snags with diameter greater than 20 cm were the smallest part of WD. The situation of WD in this region reflects the structural
characteristics of WD in mid-late stage of plateau-type karst evergreen and deciduous broad-leaved mixed forest succession.
The potential contribution of WD to the regional carbon cycle, and its relationship with climate change were finally discussed. The WD
(especially CWD) plays an important role in the carbon cycle of karst forest. Forest WD production and decay rates may partially
depend on climatic conditions, the accumulation of CWD and FWD carbon stocks in forests may be correlated with climate.
Uncertainty Analysis for Southwest Forest Biomass and Carbon Stocks Using Active and Passive Remote Sensing
Zhuoting Wu, Barry Middleton, John Vogel and Dennis G Dye
On the San Carlos Apache Reservation in east-central Arizona, fire suppression and other factors have led to overstocked forests and
woodlands, and woodland encroachment into grasslands. In an effort to retain traditional relationships with the land, the San Carlos
Apache Tribe is working to restore the land to approximate pre-European settlement conditions using a combination of mechanical
thinning and fire. Restoring the historic fire return interval in forests and woodlands with the current unnaturally high fuel loads in times
of prolonged drought is a challenge in the Southwest US, and therefore creating an accurate forest biomass baseline is very important
for future carbon balance projections considering ongoing climate change. Forest aboveground biomass was estimated from active and
passive remote sensing sources including high point density airborne lidar, high and moderate spatial resolution WorldView-2 and
Landsat 8 satellites. General (all species inclusive) and species-specific biomass models were created using active and passive remote
sensing data sources. Across all species, lidar derived height and intensity metrics in combination provided the most robust estimate for
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aboveground biomass, producing models with R-square values above 0.8 and RMSE less than 14 Mg ha . Landsat 8 based species-1
specific aboveground biomass models yielded errors ranging from 9 to 28 Mg ha , whereas WorldView-2 based model yielded errors of
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17 to 44 Mg ha . Structural information extracted from lidar provided accurate estimates for fine-scale aboveground biomass mapping,
while spectral information derived from Landsat 8 can be used for large scale biomass mapping beyond lidar spatial coverage. Long
term forest carbon records could be used to direct forest resource management efforts (e.g., thinning and burning) to avoid catastrophic
fires, retain stored carbon and maintain long-term carbon sink strength of forest ecosystems.
Uncertainties in forest soil carbon and nitrogen estimates related to soil sampling methods in the Delaware River Basin
Bing Xu, Alain F Plante, Arthur H Johnson and Yude Pan
Estimating forest soil carbon and nitrogen (CN) is critical to understanding ecosystem responses to changing climate, disturbance and
forest management practices. Most of the uncertainty in soil CN cycling is associated with the difficulty in characterizing soil properties
in field sampling because forest soils can be rocky, inaccessible and spatially heterogeneous. A composite coring technique is broadly
applied as the standard FIA soil sampling protocol. However, the accuracy of this method might be limited by soil compaction, rock
obstruction and plot selection problems during sampling. In contrast, the quantitative soil pit sampling method may avoid these
problems and provides direct measurements of soil mass, rock volume and CN concentration representative of a larger ground surface
area. In this study, the two sampling methods were applied in 60 forest plots, randomly located in three research areas in the Delaware
River Basin in the U.S. Mid-Atlantic region. In each of the plots, one quantitative soil pit was excavated and three soil cores were
collected. Our results show that average soil bulk density in the top 20 cm mineral soil measured from the soil cores was consistently
lower than bulk density measured by soil pits. However, the volume percentage of coarse fragments measured by the core method was
also significantly lower than the pit method. Conversely, CN concentrations were greater in core samples compared to pit samples. The
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resulting soil carbon content (0-20 cm) was estimated to be 4.1 ± 0.4 kg m in the core method compared to 4.5 ± 0.4 kg m in the pit
method. Lower bulk density but higher CN concentration and lower coarse fragments content from the cores have offset each other,
resulting in no significant differences in CN content from the soil pit method. Deeper soil (20-40 cm), which is not accessible in the core
method, accounted for 29% of the total soil carbon stock (0-40 cm) in the pit method. Our results suggest that, although soil CN stocks
measured by the two sampling methods had no significant difference, some systematic biases appear to exist in the FIA soil core
method in measuring soil bulk density and coarse fragment content. Data collected by the quantitative soil pit method may be
considered more accurate and can access greater soil depth, but substantially labor intensity may hamper sample sizes.
Uncertainty in accounting for carbon accumulation following forest harvesting
Ruth D. Yanai, Paul Lilly, Mary A Arthur, Kikang Bae, Steven Hamburg, Carrie R Levine, and Matthew A Vadeboncoeur
Tree biomass and forest soils are both difficult to quantify with confidence, for different reasons. Forest biomass is estimated nondestructively using allometric equations, often from other sites; these equations are difficult to validate. Forest soils are destructively
sampled, resulting in little measurement error at a point, but with large sampling error in heterogeneous soil environments, such as in
soils developed on glacial till. In this study, we report C contents of biomass and soil pools in northern hardwood stands in replicate
plots within replicate stands in 3 age classes following clearcut harvesting (14-19 yr, 26-29 yr, and > 100 yr) at the Bartlett Experimental
Forest, USA. The rate of C accumulation in aboveground biomass was ~3 Mg/ha/yr between the young and mid-aged stands and <1
Mg/ha/yr between the mid-aged and mature stands. We propagated model uncertainty through allometric equations, and found errors
ranging from 3-7%, depending on the stand. The variation in biomass among plots within stands (6-19%) was always larger than the
allometric uncertainties. Soils were described by quantitative soil pits in three plots per stand, excavated by depth increment to the C
horizon. Variation in soil mass among pits within stands averaged 28% (coefficient of variation); variation among stands within an age
class ranged from 9-25%. Variation in carbon concentrations averaged 27%, mainly because the depth increments contained varying
proportions of genetic horizons, in the upper part of the soil profile. Differences across age classes in soil C were not significant,
because of the high variability. Uncertainty analysis can help direct the design of monitoring schemes to achieve the greatest
confidence in C stores per unit of sampling effort. In the system we studied, more extensive sampling would be the best approach to
reducing uncertainty, as natural spatial variation was higher than model or measurement uncertainties.