SMC Quarterly News
www.standmgt.org
Stand Management Cooperative
College of Forest Resources, University of Washington
2nd Quarter 2008
From the Director
This past quarter was noteworthy for the extreme weather conditions. The blowdown and heavy snows have created access issues
for the field crew but it appears that work will be completed on
time. During the past quarter, we have been busy planning for
the Spring and Fall Meetings, developing research proposals,
planning summer field work and hiring the summer field crew,
Dave Briggs, SMC Director
and inspecting and setting up sites for the new paired-tree
fertilization installations. Brief summaries of these activities are in
the following sections. The feature article in this issue is a summary of the carry-over effect study by graduate student Paul
Footen.
SMC Spring and Fall Meeting
The Spring Meeting will be on April 22-23 at the Gifford Pinchot
National Forest Headquarters in Vancouver, WA. The agenda for
the 22nd will include a business meeting followed by research
presentations. The meeting will begin at 9:00 and end at 5:00.
The 23rd will be a workshop on the first release of the Young Stand
Model. The workshop will begin at 8:30 am and conclude by
4:00 pm. Registration for each day is separate this year, contact
Megan O’Shea to register for them (moshea@u.washington.edu).
inside:
From the Director
1
This workshop will introduce users to the execution and func-
Long-term Effects of Nitrogen
Fertilization on Productivity 3
tional behavior of the CONIFERS young stand simulator. Both the
Abstracts and Publications
15
graphical user interface and the DLL will be presented. There will
Meetings
17
be a brief introduction to the original SWO (variant) but the main
focus will be the SMC variant. Installation, file I/O, management
options (thinning, shrub control and genetic gain) will be covered. ORGANON - specific linkage issues will be covered as well.
Attendees should bring a laptop computer and have administrative access to allow installation of the simulator.
The Fall Meeting will be held on September 16-17 at the Little Creek
Casino in Kamilche, WA. near Shelton and the site of our 2004 Fall Meeting. The 16th will include a business meeting and research presentations.
The 17th will be a field trip to visit one of the genetic-gain/type IV
(GGTIV) installations, the Matlock long-term site productivity experiment,
and either a Type III installation of possibly a new Type V installation. Type
V is the designation for the series of new paired tree fertilization installations.
Paired-tree Fertilization Installations (Type V)
As of this writing we have 6 installations where the trees have been
measured, pairings have been made, and fertilizer has been applied. We
also have 7 other sites that have been visited and accepted but measurements and pairings have not been done due to access related to snow and
blowdown. Of those that have been set up PhD student Kim Littke has
been installing sensors to record temperature and precipitation.
Agenda 2020 Proposals
During the past quarter many of us were involved in preparing proposals
for the FY08-10 funds dedicated to the AF&PA-USFS Agenda 2020 collaboration. One of the finalists is a joint venture between the SMC and
the CIPS paired tree fertilization studies.
Management of PNW forest plantations: Additional site
characterization and instrumentation for SMC/CIPS
Paired-Tree Fertilization Projects. By Rob Harrison1, Doug
Maguire2, Eini Lowell3, Dave Briggs1, Doug Mainwaring2, Eric
Turnblom1 and Kim Littke1. 1SMC-Univ. of Washington, 2CIPSOregon State University, 3USFS-Portland. This project seeks funding
associated with the new paired tree fertilization studies. The design
for these was outlined in the 4th Quarter Issue.
2
Mark Your Calendars
The SMC Spring Meeting will be
on April 22-23, 2008, at the
Gifford Pinchot National Forest
Headquarters in Vancouver, WA.
More info can be found on the
SMC web site: www.standmgt.org
Center for Advanced Forest Systems (CAFS)
SMC Director Dave Briggs and Silviculture Project Leader Eric Turnblom
participated in a CAFS field trip on February 21. CAFS is funded through
the National Science Foundation’s Industry-University Cooperative
Research Centers program. NSF’s objective is to foster collaboration and
formation of cooperative efforts. Universities that are current members
of CAFS are North Carolina State University, Oregon State University,
Purdue University, and Virginia Tech. Since a number of forestry cooperatives and centers already exist at these and other Universities, CAFS will
focus on improved communication and collaboration among these existing organizations rather than formation of new ones. During the CAFS
field trip the SMC was strongly encouraged to develop a University of
Washington proposal to join CAFS. We are presently working on the
proposal.
New Members
The SMC has two new members. Roseburg Resources has joined and
David Walters will be their representative on the Policy Committee.
Renewable Resources, LLC has joined and Harry Bell will be their representative on the Policy Committee.
Summer Field Crew
The summer 08 field crew will be Graduate Students Paul Footen and
Kim Littke and Natalie Schmidt who will graduate in June with a BS in
Biology and a Minor in Environmental Science and Resource Management.
One of the key tasks will be to conduct site characterization of the three
genetic-gain/type IV (GGTIV) installations that were planted in 2006. Last
summer’s crew performed this work on the GGTIV’s planted in 2005.
Visits to other installations will obtain understory vegetation/habitat
characterization data, dig soil pits, and gather tree acoustic velocity data.
3
Long-term Effects of Nitrogen
Fertilization on Productivity of
Subsequent Stands of Douglas-fir
(Psuedotsuga menziessii [Mirb.] Franco) in
the Pacific Northwest
P.W. Footen , R.B. Harrison and B.D. Strahm
Abstract
The long-term, or carryover, effects of nitrogen (N) fertilizations on the
productivity of subsequent stands of Douglas-fir (Psuedotsuga menziessii
[Mirb.] Franco) were quantified on five sites in the Puget Sound Region of
western Washington. Average height and diameter at breast height (DBH)
of 7-9 year old Douglas-fir trees and biomass and N-content of understory vegetation were assessed on paired control (untreated) and N
fertilized plots that had received cumulative additions of 810-1120 kg N
ha-1 to the previous stand. Overall productivity was significantly greater in
the previously fertilized plots than in the controls. In 2006, the last growth
measurement year, mean seedling height was 15% greater (p = 0.06) and
mean DBH was 29% greater (p = 0.04) on previously fertilized plots than
on control plots. Understory vegetation biomass was 73% greater (p =
0.005), and N-content was 97% greater (p = 0.004) than on control plots.
These results show that past N fertilization markedly increased seedling
growth, and biomass and N-content of understory vegetation in a subsequent rotation. These findings suggest that N fertilization can potentially
increase site productivity of Douglas-fir stands in the Pacific Northwest
15-22 years after application. These trends should continue to be monitored, and similar studies should be established, to further understand the
carryover effects of N fertilization on subsequent stands.
Introduction
Forest growth in the Pacific Northwest is limited by the supply of plant
available N (Gessel et al., 1973; Chappell et al., 1991). As demand for
wood products increases, commercial timberlands in the region continue
to shrink in response to land-use restrictions and conversion into other
uses putting further pressures on the sustainable supply of forest products in the Pacific Northwest. Increasing current and future productivity
of timberlands by means of N fertilization may be necessary to insure the
sustainability of the forest products industry in the region.
4
Several studies have shown that N fertilization of second and third
growth Douglas-fir stands can increase growth and has become an industry standard for increasing forest productivity (Gessel and Walker, 1956;
Edmonds and Hsiang, 1987; Stegemoeller and Chappell, 1990; Chappell et
al., 1991). Prior studies from Binkley (1986) and Miller (1988) have shown
beneficial effects of N fertilizer when applied to N-limited forest ecosystems on N availability and stand productivity to generally last no longer
than 5-10 years. N fertilization also increases the amount of foliar N
(Heilman and Gessel, 1963; Turner, 1977) and total N (Pang et al., 1987) in
Douglas-fir trees and understory vegetation (Abrams and Dickmann,
1983; Matsushima and Chang, 2007; VanderSchaaf et al., 2004). Postharvest retention of organic material, such as needles and branches, may
be an important pool of available nutrients to subsequent stands (Mann et
al., 1988). However, the carryover effects of repeated N fertilization and
organic matter retention on subsequent stand productivity are not well
known.
The objectives of this study were to quantify the carryover effects of
previous N fertilizations on subsequent stands of Douglas-fir. Biomass and
N-content of understory vegetation, and height and diameter of Douglasfir trees have been measured to assess these possible effects. Understanding the carryover effects of N fertilization, organic mater retention and
the combined secondary effects of both practices could provide forest
managers with better treatment strategies to maintaining and increasing
long-term productivity and sustainable yields.
Methods and Materials
Study sites
These five sites began as fertilization trials of the former Regional Forest
Nutrition Research Project (RFNRP), now integrated into the Stand
Management Cooperative (SMC). In the late 1960’s and the early 1970’s,
N fertilization trials were established by the RFNRP to study the effects
of repeated N fertilization on stand growth. The SMC continues to
monitor multiple replicated fertilization sites that are now reaching
harvest age after having demonstrated increased growth and other effects
of N fertilization on forest productivity. Instead of protecting these
stands from harvest, this study was initiated to examine the potential
carryover effects of fertilization on subsequent rotations.
The study sites are located in the Puget Sound Area of Western Washington, and belong to the Tsuga heterophylla [Raf.] Sarg. Zone described by
Franklin and Dyrness (1988). This zone is characterized by a wet, mild
maritime climate, with moderate moisture stress during summer. Mean
5
annual air temperatures average 9-10 °C. Depending on the topographic
location, annual precipitation for the study sites range between 1000 and
2900 mm. The study sites differ considerably in elevation, slope, and aspect
(Table 1).
At four sites (Coyle, Hank’s Lake, Simpson Log Yard and Camp Grisdale), the
parent material is exclusively or predominantly glacial outwash. Soils are
Dystric Xerochrepts of the Everett series with sandy, skeletal texture. At
Pack Forest, where the parent material is andesite colluvium, the soil is a
fine-loamy Ultic Haploxeralf of the Wilkeson series. At Camp Grisdale, where
parent material is old alluvium and glacial drift, fine-loamy Umbric
Dystrochrepts of the Hoquiam series have been formed. All study sites were
fully stocked with second growth, pure Douglas-fir seedlings (Table 2).
Experimental treatments
The RFNRP/SMC installed multiple plots 0.04 ha in size at each study site
(rectangular plots at Cedar River and Camp Grisdale; square plots at other
sites). All installations included at least one (untreated) control plot and at
least one adjacent plot fertilized repeatedly with urea. Treatment plots were
fertilized with an initial application of 448 kg N ha-1 followed by repeated
applications of 224 kg N ha-1 at consecutive intervals of eight, four and four
years. In total, 1120 kg N ha-1 were applied Camp Grisdale, Coyle, and
Simpson Log yard sites, while Pack Forest received 896 kg N ha-1 total (Table
1). The mature timber on all plots was harvested between 1997 and 1999,
with replanting of Douglas-fir seedlings following soon after (Table 2). At the
time of harvest the RFNRP/SMC study plots were re-monumented, and all
corners marked. Tops and foliage were removed from harvested timber,
returned to the plots of origin and scattered evenly within the boundaries of
the study areas by hand. In 2006, at the time of this study, crop trees ranged
in age from 7 to 9 years.
6
Table 1
Description of Carryover study sites
Camp Grizdale
Latitude
Longitude
Elevation (m)
Precipitation (mm)
Slope, aspect
47 15'4"N
123 35'31"W
420
290 0
15%, W
Old alluvium, glacial
Parent Material
drift
Um bric
Dystrochrept, fin eSoil type, tecture
loamy
Stand Establishment 194 1
SI 50 (m)
38
Pack Forest
Coyle
46 50'2 "N
122 17 '38"W
548
1000
40%, S
47 50'56"N
122 45'25"W
189
100 0
20%, SE
Collu vial an desite
Glacial outwash
Sim pson Log Yard
47 14'2 5"N
123 15 '50"W
152
1800
Flat
Glacial outwash +
tephra
Hank's Lake
4 7 18'34"N
1 23 16'54 "W
1 77
2 000
Flat
Glacial outwash
Ultic Haplox eralph, Dy stric Xero chrept, Dystric Xerochrept, Dystric Xerochrept,
fine-loamy
sandy, skeletal
sand y, skeletal
sandy, skeletal
1930
30
193 7
33
1923
29
1 920
20
Table 2
Experimental treatment regimes at the different Carryover study sites
Camp Grizdale
Installation establish ment
(year)
196 9
Fertilization (kg N ha -1 )
Fertilization d ates
Fertilizatiion regime (k g N ha
Pack Forest
1 972
Coyle
1972
Simpson Log Yard
19 75
Hank's Lake
1975
0/112 0
0 /896
196 9-197 7-198 11 972-1 980-1 984
198 5
0/1120
0/11 20
1972-1980-1984 - 19 75-19 83-19 871988
19 91
0/1120
1975-1983-19871991
448 -224-224-224
4 48-22 4-224
448-224-2 24-22 4
44 8-224 -224-224
448-2 24-22 4-224
Jul-9 9
58
Jul-9 9
Mar-97
67
Mar-97
Dec-98
61
Jan-99
Jan-99
76
Jun-99
Mar-99
79
Jun-9 9
21
22
18
15
15
-
1
)
Date of logging (month/year)
Stand age at harvest (years)
Date of planting (month/year)
Time elapsed between last
fertilization an d study (years)
7
Vegetation sampling and analysis
A stratified random sample point location was used to identify understory
vegetation sampling points. Two random numbers were selected from a
random number table. Starting in the northeast corner of each plot, the
first number chosen was used as the distance along the x-axis (east-west)
and the second was used as the distance along the y-axis (north-south). Five
random sample point locations (sub-plots) were identified for each plot.
Vegetation was clipped to the ground using hand sheers or scissors in each
of the five 0.25 m2 sub-plots.Vegetation for determining biomass was harvested from the three dimensional volume of the quadrat (height x width x
length). Parts of the plants that were rooted within the quadrat but did not
occupy space within the cubic volume were not harvested, while plants that
were not rooted within the quadrat but overlapped into the volume were
harvested to the point of overlap with the sample boundary.
Understory plant material from the biomass sampling was dried to a constant weight at 70 °C and weighed to determine biomass on a sub-plot level.
The mean of the five sub-plot vegetation samples were then extrapolated up
to represent understory biomass and the kg ha-1 level. Afterward, all samples
were finely ground to 1 mm using a Wiley mill for subsequent N analysis.
Total N concentration was determined by dry combustion (Perkin-Elmer
CHN Analyzer Model 2400, Norwalk, CT). Nitrogen content for each
sample was determined by multiplying the average N concentration by the
biomass. Plot level N contents were calculated by summing all the subplots
in each plot. Tree heights and diameter at breast height (DBH) were recorded in the study plots after each growing season (every Fall) from 19972006 (except in 2004).
Statistical analyses were performed on data at the installation-level using the
Student’s paired-sample t-test. Since each installation contained only one
control plot and one treatment plot, statistical analyses for individual sites
were limited.
Results and Discussion
Mean tree height and DBH on the previously fertilized plots were significantly different than the controls (Figures 1 and 2) beginning in 2001 and
2005, respectively. The differences in height were statistically significant (p <
0.1) every year measured from 2001 to 2006 with a mean tree height 15%
greater (p = 0.06) in the fertilized plots. Mean DBH was statistically significant in 2005 and 2006. In the last growth measurement year (2006), DBH
was 29% greater (p = 0.04) on the previously fertilized plots than on the
controls.
8
4
Fertilized
Control
3.5
3
2.5
2
1.5
1
0.5
0
1996
1997
1998
1999
2000
2001
2002
2003
2004
2005
2006
2007
Year
Figure 1
Mean height (m) of Carryover study Douglas-fir trees. The differences in height were
statistically significant (p < 0.1) every year measured from 2001 to 2006. In 2006
mean tree height was 15% greater on the previously fertilized plots than on the
control. Control points are offset to show (+/- 1) standard error bars.
4.5
Fertilized
Control
4
3.5
3
2.5
2
1.5
1
0.5
0
1998
1999
2000
2001
2002
2003
2004
2005
2006
2007
Year
Figure 2
Mean DBH (cm) of Carryover study Douglas-fir trees. The differences in DBH were
statistically significant (p < 0.1) in years 2005 and 2006. In 2006 mean DBH was 29%
greater on the previously fertilized plots than on the control. Control points are
offset to show (+/- 1) standard error bars.
9
The carryover effects of N fertilization on understory biomass and N-content were
also significantly greater in the previously fertilized plots (Figs 3 and 4). Understory
biomass on the previously fertilized plots was 73% greater (p = 0.005) (Figure 3).
Understory N-content was 97% greater (p = 0.004) than the control (Figure 4).
10000
9000
Biomass (kg ha-1)
8000
7000
6000
5000
4000
3000
2000
1000
0
Fertilized
Control
Figure 3
Biomass for understory vegetation on Carryover study sites. The differences in biomass of understroy were statistically significant (p < 0.1) in 2006. Understory biomass
was 73% greater on the previously fertilized plots than on the control.
10
120
N-content (kg ha-1)
100
80
60
40
20
0
Fertilized
Control
Figure 4
Nitrogen content of understory vegetation on Carryover study sites. The differences in N-cintent of understroy were statistically significant (p < 0.1) in 2006. In
2006 understory N-content was 97% greater on the previously fertilized plots than
on the control.
Previous studies indicate that the effects of N fertilization on stand productivity are
temporary, generally lasting only 5-10 years (Binkley and Reid, 1985; Strader and
Binkley, 1989; Prescott et al., 1995; Priha and Smolander, 1995; Smolander et al.,
1998; Nohrstedt et al., 2000). This study shows that N fertilization, coupled with
organic matter retention from bole only tree removal harvest practices, increases
productivity of subsequent stands 15-22 years after the last application. This
carryover phenomenon, to our knowledge, has not been studied and the mechanisms driving these prolonged effects of N fertilization are not well known.
Studies have shown assessment of existing understory vegetation can be used to
estimate soil N availability (Klinka et al., 1989). In this study biomass and N-content
of understory vegetation on previously fertilized plots increased 73% and 93%,
respectively (Figs 3 and 4). These results agreed with observations from other
studies. Heilman and Gessel (1963) reported increased N content of understory
vegetation following fertilization. Turner (1979) measured increased understory
biomass and N content, while Canary (1994) observed increased aboveground
production with fertilization. Increase in biomass and N-content of understory
vegetation not only produces greater quantities and higher quality liter fall, but can
also increase N uptake which can decrease N leaching and help retain N on site.
11
This process coupled with the retention of N-rich organic is likely driving
the increases in productivity of Douglas-fir trees on the previously fertilized plots.
Use of N-fertilization could potentially satisfy multiple natural resource
management objectives; from increasing growth and yield of primary and
secondary forest products to increase in quality and abundance of wildlife
habitat. To fully understand these carryover effects it is important to
continue long-term monitoring of these sites. Additionally, quantifying the
soil and foliar N-pools would give estimates of the total N-budgets for
the sites and the region. Further study of this phenomenon will ultimately
give forest managers a better understanding of how to use the valuable
tool of N-fertilization to reach their objectives.
Conclusions
12
•
Previous N fertilization increased subsequent productivity of
stands of Douglas-fir in the Pacific Northwest region. The effects
of N fertilization can last much longer than previously understood.
This carryover effect implies that N fertilizer response is not
ephemeral in all cases especially in forests in this region.
•
N fertilization increased height and DBH of Douglas-fir crop trees
on subsequent rotations. In the last year measured (2006) mean
height and DBH were 15% and 29% greater respectively than the
unfertilized controls. The differences in mean height were statistically significant (p < 0.1) annually from 2001 to 2006 and mean
DBH was statistically significant in 2005 and 2006.
•
Biomass and N-content of understory vegetation on previously
fertilized plots increased and were 73% and 93% greater respectively than control plots in 2006.
•
Further investigation of the carryover phenomenon should be
conducted. Greater understanding of the mechanisms driving
these long-term effects of N fertilization on the productivity of
subsequent stands could aid forest managers in developing strategies to increases productivity and sustainable yields.
References
Abrams, M. D. and Dickmann, D. I., 1983. Response of understory vegetation to
fertilization on mature and clear-cut jack pine sites in Northern lower
Michigan. Amer. Mid. Natur. 110, No. 1. 194-200.
Binkley, D., 1986. Forest Nutrition Management. Wiley, New York.
Binkley, D., and P. Reid. 1985. Long-term increase of nitrogen from fertilization of
Douglas-fir. Can. J. For. Res. 15:723-724.
Binkley, D., and P. Reid. 1985. Long-term increase of nitrogen from fertilization of
Douglas-fir. Can. J. For. Res. 15:723-724.
Canary, J.D. 1994. Carbon and nitrogen storage following repeated urea
fertilization of a second growth Douglas-fir stand in western Washington. MS
Thesis. Univ. of Washington.
Chappell, H.N., D.W. Cole, S.P. Gessel & R,B. Walker. 1991. Forest fertilization
research and practice in the Pacific Northwest. Fertilizer Research 27: 129140. Edmonds R.L., and T. Hsiang. 1987. Forest floor and soil influence on
response of Douglas-fir to urea. Soil Sci. Soc. Am. J. 51:1332-1337.
Franklin, J.F., and C.T. Dyrness. 1988. Natural vegetation of Oregon and
Washington. Oregon State Univ. Press, USA.
Gessel, S.P., D.W. Cole, and E.C. Steinbrenner. 1973. Nitrogen Ballances in forest
ecosystems of the Pacific Northwest. Soil Biol. Biochem. 5;19-34.
Gessel, S.P., and R.B. Walker. 1956. Height growth response of Douglas-fir to
nitrogen fertilization. Soil Sci. Soc. Am. Proc. 20:97-100.
Heilman, P.E., and S.P. Gessel. 1963. The effect of nitrogen fertilization on the
concentration and weight of nitrogen, phosphorus, and potassium in Douglasfir trees. Soil Sci. Soc. Am. Proc. 27:102-105.
Klinka, K.,V.J. Krajina, A. Ceska and A.M.Scagel. 1989. Indicator plants of coastal
British Columbia. University of British Columbia Press,Vancouver.
Mann, L., Johnson, D., West, D., Cole, D., Hornbeck, J., Martin, C., Riekerk, H., Smith,
C., Swank, W., Tritton, L., Lear, D., 1988. Effects of whole-tree and stem-only
clearcutting on postharvest hydrologic losses, nutrient capital, and regrowth.
Forest Science. 24, No. 2. 410-428.
13
Matsushima, M. and Chang, S., 2007. Effects of understory removal, N fertilization,
and litter lay removal on soil N cycling in 13-year-old white spruce
plantation infested with Canada bluejoint grass. Plant Soil. 292, 243-258.
Miller, H.G. 1988. Long-term effects of application of nitrogen fertilizers on
forest sites. In D.W. Cole and S.P. Gessel (ed.) Forest site evaluation and
long-term productivity. Univ. of Washington Press, Seattle: 97-106.
Nohrstedt, H.O., Jacobsen, S., Sikstrom, U., 2000. Effects of repeated urea doses
on soil chemistry and nutrient pools in a Norway spruce stand. For. Ecol.
Manage. 130, 47-56.
Pang, P.C., H.J. Barclay, and K.M. McCullough. 1987. Aboveground nutrient
distribution within trees and stands in thinned and fertilized Douglas-fir.
Can. J. For. Res. 17:1379-1384
Prescott, C.E., B.E. Kischchuk, and G.F. Weetman. 1995. Long-term effects of
repeated nitrogen fertilization and straw application in a jack pine forest
Nitrogen availability in the forest floor. Can. J. For. Res. 25:1991-1996.
Priha, O., Smolander A., 1995. Nitrification, denitrification and microbial biomass
N in soil from two N-fertilized and limed Norway spruce forests. Soil Biol.
Biochem. 27, 305-310.
Smolander, A., Priha, O., Paavolainen, L., Steer, J., Malkonen, E., 1998. Nitrogen and
carbon transformations before and after clear-cutting in repeatedly Nfertilized and limed forest soil. Soil Biol. Biochem. 16, 957-962.
Stegemoeller, K.A., and H.N. Chappell. 1990. Growth response of unthinned and
thinned Douglas-fir stands to single and multiple applications of nitrogen.
Can. J. For. Res. 20:343-349.
Strader, R.H. and D. Binkley. 1989. Mineralization and immobilization of soil
nitrogen in two Douglas-fir stands 15 and 22 years after nitrogen
fertilization. Can. J. For. Res. 19:798-801.
Turner, J. 1977. Effect of nitrogen availability on nitrogen cycling in a Douglas-fir
stand. Forest Sci. 23:307-316.
Turner, J, 1979. Effects of fertilization on understory growth. Proceedings Forest
Fertilization Conference.
VanderSchaal, C., Moore, J., Kingery, J., 2004. The effect of multi-nutrient
fertilization on understory vegetation nutrient concentrations in inland
Northwest conifer stands. For. Ecol. Manage. 190, 201-218.
14
Abstracts and Publications
Modeling dynamics of competing vegetation in young conifer plantations of
northern California and southern Oregon, USA. Martin W. Ritchie and Jeff
D. Hamann. Can. J. For. Res. 36(10): 2523–2532 (2006).
Abstract
This paper describes the development of growth equations for competing vegetation
in young conifer plantations, consistent with an individual-tree growth model architecture. Response variables were height increment, basal diameter increment, and change
in crown width for a 2-year growth interval. The results for three common competing
shrub and three competing hardwood species are presented. Fit statistics for hardwoods were generally much better than those obtained for shrub species. Crown
width growth equations generally had very poor fit statistics. Static crown equations
also relate crown area to plant height. The equations were developed for use in an
individual-tree plant growth model for young plantations.
Applications of modeling to vegetation management. Euan G. Mason and
Helge Dzierzon. Can. J. For. Res. 36(10): 2505–2514 (2006).
Abstract
A review of modeling applied to vegetation management shows that these models
range in resolution from simple yield equations to complex representations of processes affecting growth and competition for light, water, and nutrients. The latter
models inform scientists and managers about mechanisms involved, while the former
are more likely to be applied by managers to estimate effects of competition. Six
generic model forms were identified. Models may be further categorized by whether
they focus on weed population dynamics or on processes directly affecting growth of
crop plants. There is scope for these aspects of vegetation modeling to be combined.
Extremely complex models are scientifically satisfying as repositories of knowledge, but
they tend to be excessively parametarized and recursive. Models with many parameters are difficult to fit to specific situations because they are ambiguous; the same
overall estimates of growth can be achieved in a variety of ways. In addition, their
recursive nature leads to compounded errors. Simple growth and yield models, by
contrast, are usually very efficient and accurate at estimating local estimates of growth,
but they are inadequately sensitive to the variety of site and site management practices
that vegetation managers wish to represent. A new kind of hybrid model is proposed
that combines the efficiency of forest mensurational techniques with sufficient complexity to represent the results of scientific studies associated with vegetation management for use by managers.
15
Abstracts and Publications cont.
Twelfth-year response of Douglas-fir to area of weed control and herbaceous versus woody weed control treatments. Robin Rose, Lee S. Rosner,
and J. Scott Ketchum. Can. J. For. Res. 36(10): 2464–2473 (2006).
Abstract
Coastal Douglas-fir (Pseudotsuga menziesii (Mirb.) Franco var. menziesii) response
to eight weed control treatments was measured 12 years after planting at two
Oregon sites. Treatments included four areas of weed control around individual
trees (0.375, 1.49, 3.35, and 5.95 m2), no weed control (check), total vegetation
control, control of herbaceous competition only, or control of woody competition
only. Douglas-fir growth and woody-species invasion differed between the Coast
Range site (Summit) and the Cascade Range foothills site (Marcola). Woody species
reinvasion was more intense at Summit, with Douglas-fir cumulative mortality in the
check treatment reaching 23% in year 12. Woody-only control improved Douglas-fir
growth at Summit but had no significant effect on growth at Marcola. Total vegetation control had a profound effect on stem volume growth 12 years after planting.
At Summit, total vegetation control resulted in a 355% increase in volume per
hectare relative to the check. At Marcola the increase was only 63%. At Summit,
growth increased with each increase in area of weed control, whereas at Marcola
growth increased with increasing area of weed control up to 3.35 m2 of control.
Results suggest that much of the gain in volume growth attributable to weed
control may be lost if weed-control treatments are not highly efficacious. The
differential response to woody control indicates that its benefit at a given site is
strongly related to the abundance of competitive hardwood species, which may be
predicted from the preharvest stand structure and vegetation community.
Comparing power among three sampling methods for monitoring forest
vegetation. Sarah E. Johnson, E. L. Mudrak, E. A. Beever, S. Sanders, and D.
M. Waller. Can. J. For. Res. 38(1): 143–156 (2008).
Abstract
We compared three methods of sampling forest vegetation for their ability to
reliably estimate changes in species richness, plant abundance, and overstory basal
area and composition. Methods include the US Forest Service’s Forest Inventory
and Analysis (FIA) method and two other methods being considered for use in
monitoring National Parks in the Northern Great Lakes ecoregion. All methods
were successful at detecting changes in composite variables but lacked sufficient
enough power to detect a 20% change in the abundance of most individual species.
All three methods had high power for detecting changes in overstory tree communities but differed greatly in their ability to track shifts in understory composition
and diversity. Although complete walk-through surveys of all species present provided adequate power for tracking changes in diversity, sampling only 12 ground
layer quadrats limited the power of the FIA method. Methods that sample the
understory more intensively provide a better balance of sampling effort and provide
higher power to detect changes in forest understory communities. Aggregating data
across sites of similar habitat also provides more powerful estimates of change.
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Upcoming Meetings and Events
April 22-23, 2008. SMC’s Annual Spring Meeting. Gifford Pinchot National Forest
Headquarters in Vancouver, WA. Registration info: www.standmgt.org
May 13-14, 2008. Forest Biomass Utilization:The Impact on Forest Resources.
Red Lion Hotel at the Park, Spokane, WA. Registration info: 503-226-2515
www.westernforestry.org
May 27-28, 2008. Two Wood Quality Workshops. Vancouver WA. Sponsored by:
Pacific Northwest Tree Improvement Cooperative, Stand Management Cooperative, and
Northwest Tree Improvement Cooperative. Registration info: 503-226-2515
www.westernforestry.org
2008 Western Mensuration Conference, June 22-24, 2008. Eagle Creek Resort,
Redmond, OR. Registration info: www.westernforestry.org/wmens/
July 21-24, 2008. Joint Conference of the Southern Forest Nursery Association
and the Northeast Forest and Conservation Nursery Association. Asheville,
North Carolina. Registration info: 503-226-2515 www.westernforestry.org
Sept 21-24, 2008. SMC’s Annual Fall Meeting. Little Creek Casino
Kamilche, WA. Registration info: www.standmgt.org
Stand Management Cooperative, College of Forest Resources
University of Washington, Box 352100 Seattle, WA 98195
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