Grantee Research Project Results
2002 Progress Report: Regional Analysis of Net Ecosystem Productivity of Pacific Northwest Forests: Scaling Methods, Validation and Results Across Major Forest Types and Age Classes
EPA Grant Number: R828309Title: Regional Analysis of Net Ecosystem Productivity of Pacific Northwest Forests: Scaling Methods, Validation and Results Across Major Forest Types and Age Classes
Investigators: Law, B. E. , Harmon, M. E. , Daly, Christopher , Turner, D. , Unsworth, M. , Cohen, W.
Institution: Oregon State University
EPA Project Officer: Packard, Benjamin H
Project Period: July 1, 2000 through June 30, 2003 (Extended to June 30, 2004)
Project Period Covered by this Report: July 1, 2002 through June 30, 2003
Project Amount: $1,848,927
RFA: Regional Scale Analysis and Assessment (1999) RFA Text | Recipients Lists
Research Category: Aquatic Ecosystems , Ecological Indicators/Assessment/Restoration
Objective:
The objectives of this research project are to: (1) develop and test a regional scale approach that combines modeling, data from remote sensing, sample surveys, and intensive research sites to better estimate variation in the carbon balance of forest ecosystems in the Pacific Northwest; and (2) apply our strategy to investigate how processes controlling variation in net ecosystem productivity are influenced by forest development, disturbances, and contrasting climatic conditions.
Progress Summary:
To assess the relative influence of mesoclimate stand replacing disturbance on the Net Ecosystem Productivity (NEP) of Oregon forests, we used biometric techniques to measure NEP at 36 independent forest plots arranged as 3 replicates of 4 age classes in each of 3 climatically distinct ecoregions. For the most part, there was no clear trend in heterotrophic respiration with age class. As such, successional trends in NEP were primarily driven by net primary production and in particular, wood production. Among stands of the same age, Oregon's climatic-edaphic gradient causes NEP to vary by 90 percent of the regional mean. Among stands in the same ecoregion, NEP varies by 140 percent over development following stand-replacing disturbance. However, disturbance history and recovery rates on this landscape are such that some developmental stages occur less frequently than others. Consequently, the regional variation in NEP attributable to disturbance is only 60 percent of the mean. The sensitivity of landscape-level NEP to shifts in age class distribution is highest in the West Cascades, lowest in the East Cascades, and intermediate in the Coast Range.
We submitted a paper to Global Change Biology (Sun, et al.) on the changes in carbon storage in mineral soils and detritus at 96 plots that represent the range of forest types in the Pacific Northwest United States. Carbon storage in soils was a power function of annual precipitation (r2 = 0.51), mean residence time of forest floor litterfall (r2 = 0.67) and net primary productivity (r2 = 0.54), and an exponential function of forest floor carbon in litter and woody detritus (r2 = 0.43). The highest rates of soil and necromass carbon turnover were recorded on mesic sites of Douglas-fir/western hemlock forests in the Cascade Mountains, with lower rates in wetter and drier habitats. Soil and necromass carbon differed by five-fold across the sampled forests in relation to site productivity. The relative contribution of necromass carbon to total ecosystem carbon decreased as a function of stand age to an equilibrium of approximately 35 percent between 150-200 years across the forest types. Soil carbon data are needed to initialize the models for predicting carbon cycling in terrestrial systems, and our data are being used in the modeling activity through look-up tables based on the relationships found in the field studies.
Our paper entitled, "Changes in carbon storage and fluxes in a chronosequence of ponderosa pine," was published in Global Change Biology (Law, et al., 2003). The paper evaluates differences in carbon budget components across 12 stands ranging in age from 9 to greater than 300 years. Net Primary Productivity (NPP), heterotrophic respiration, and NEP were lowest in young stands, highest in stands from 100-150 years old, and slightly lower in stands older than 200 years. NEP averaged 141 g C m-2 y-1 (SD 111). Carbon storage in live mass reached a maximum of 17.4 Kg C m-2 by age 150 to 200, and was not lower in older stands, contrary to the belief that mortality leads to decreased live mass of old stands. Total ecosystem carbon storage and the fraction of ecosystem carbon in aboveground wood mass rapidly increased until 150 to 200 years and did not decline in older stands. Forest inventory data (Forest Inventory Analysis, Current Vegetation Survey) on 950 ponderosa pine plots in Oregon show that the greatest proportion of plots exist in stands approximately 100 years old, indicating that a majority of stands are approaching maximum carbon storage and net carbon uptake. Our data suggest that NEP averages approximately 150 g C m-2 y-1 for ponderosa pine forests in Oregon. About 85 percent of the total carbon storage in biomass on the survey plots exists in stands greater than 100 years, which has implications for managing forests for carbon sequestration.
Modeling Findings
In Law, et al. (book chapter in press), we showed how a spatially nested hierarchy of observations can be used to improve remote sensing estimates of vegetation characteristics, and Biome-BGC process model predictions of NPP and NEP. With the observations from the chronosequence, we constructed simple relationships describing the variation in carbon allocation to wood with stand age, and we tested the hypothesis that this variation reduces model bias in both state and flux variable comparisons to observations. We demonstrated how the field observations of foliar chemistry and wood allocation in each ecoregion improved predictions and quantified uncertainty in the observations and model output.
We also explored the variability in disturbance recovery responses related to atmospheric CO2 concentration during recovery (Law, et al., 2003). The timing of initiation of young stands following stand-replacing disturbance had a significant effect on model estimates of NEP in the early years of stand development. The simulated response in NEP during the first 100 years following disturbance had a strong dependence on the atmospheric concentration of CO2, which varied according to the historical timing of disturbances at different stands in the chronosequence. The peak carbon sink strength was higher and occurred sooner following disturbance for the more recently disturbed stands. The effect of CO2 on carbon cycling interacts strongly with the variation in available soil mineral nitrogen, which increases after disturbance because of reduced plant demand. The observations suggested new parameterizations that have improved our ability to simultaneously estimate carbon pools and fluxes in this system. We found that accurate simulation requires a dynamic parameterization for biomass allocation that depends on stand age and should also include a representation of competition between multiple plant functional types for space, water, and nutrients. These modifications now stand as new hypotheses to be tested for generality in other systems and with additional types of observations. In Turner, et al. (in press, 2003), we used our NEP scaling approach based on remote sensing and modeling to map NEP in two ecozones in western Oregon. The two ecozones differed in land use and in their rates of carbon sequestration. The Coast Range Ecozone is heavily managed for timber production and correspondingly has a relatively young age class distribution and a high mean NEP. However, carbon is being removed from the landscape by harvesting in an amount nearly equivalent to the NEP. In the West Cascades Ecozone, much of the forestland is public and reduced logging in the last decade has led to increasing NEP and retention of carbon on the landscape. The spatially and temporally explicit nature of our NEP scaling approach permits identification of mechanisms underlying land base carbon flux.
Future Activities:
Future activities are to divide the forested region of Oregon into five ecoregions for synthesis of results. We will run the tested and newly parameterized Biome-BGC model for the entire forested region of Oregon (about 9 million hectares) and determine the relative influence of ecoregion differences in climate and disturbance on carbon stocks and fluxes of these forests. The manuscript will be submitted to a professional journal as the major synthesis of results from the U.S. Environmental Protection Agency's Science To Achieve Results (STAR) project. To encourage dynamic carbon allocation with stand age in other modeling activities globally, we will produce a manuscript on observed variation in carbon allocation with age in our chronosequences and extensive plot data across the climatic gradient, hopefully teasing out differences in allocation patterns related to species versus climate. A final modeling objective is to examine variation in carbon stocks and fluxes in relation to disturbance history and interannual variation in climate (variation in carbon stocks and fluxes over time). This will require expanding our disturbance history spatial database and a synthesis of our wood increment data. Finally, the papers that currently are in review will be revised for publication.
Journal Articles on this Report : 8 Displayed | Download in RIS Format
Other project views: | All 38 publications | 25 publications in selected types | All 24 journal articles |
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Campbell JL, Sun OJ, Law BE. Supply-side controls on soil respiration among Oregon forests. Global Change Biology 2004;10(11):1857-1869. |
R828309 (2000) R828309 (2001) R828309 (2002) R828309 (Final) |
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Cohen WB, Spies TA, Alig RJ, Oetter DR, Maiersperger TK, Fiorella M. Characterizing 23 years (1972-95) of stand replacement disturbance in western Oregon forests with Landsat imagery. Ecosystems 2002;5(2):122-137. |
R828309 (2000) R828309 (2001) R828309 (2002) R828309 (Final) |
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Cohen WB, Maiersperger TK, Gower ST, Turner DP. An improved strategy for regression of biophysical variables and Landsat ETM+ data. Remote Sensing of Environment 2003;84(4):561-571. |
R828309 (2002) R828309 (Final) |
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Kennedy RE, Cohen WB. Automated designation of tie-points for image-to-image coregistration. International Journal of Remote Sensing 2003;24(17):3467-3490. |
R828309 (2002) |
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Law BE, Turner D, Campbell J, Sun OJ, Van Tuyl S, Ritts WD, Cohen WB. Disturbance and climate effects on carbon stocks and fluxes across Western Oregon USA. Global Change Biology 2004;10(9):1429-1444. |
R828309 (2000) R828309 (2001) R828309 (2002) |
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Sun OJ, Campbell J, Law BE, Wolf V. Dynamics of carbon stocks in soils and detritus across chronosequences of different forest types in the Pacific Northwest, USA. Global Change Biology 2004;10(9):1470-1481. |
R828309 (2000) R828309 (2001) R828309 (2002) R828309 (Final) |
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Turner DP, Guzy M, Lefsky MA, Van Tuyl S, Sun O, Daly C, Law BE. Effects of land use and fine-scale environmental heterogeneity on net ecosystem production over a temperate coniferous forest landscape. Tellus Series B-Chemical and Physical Meteorology 2003;55(2):657-668. |
R828309 (2002) R828309 (Final) |
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Turner DP, Guzy M, Lefsky M, Ritts WD, Van Tuyl S, Law BE. Monitoring forest carbon sequestration with remote sensing and carbon cycle modeling. Environmental Management 2004;33(4):457-466. |
R828309 (2002) R828309 (Final) |
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Supplemental Keywords:
ecology, ecosystem, ecological effects, ecological response, ecological exposure, ecosystem assessment, ecological indicators, ecosystem indicators, ecosystem stress, ecosystem protection, carbon fluxes, remote sensing, surveys, air, environmental exposure, risk, geographic area, chemical mixtures, environmental chemistry, forestry, Pacific Northwest, scaling, state, climate change, exploratory research, environmental biology, Oregon, OR, Washington, WA, anthropogenic stresses, carbon allocation, carbon stress index, climate, forest ecosystems, forest inventory and analysis, forest resources, forests, natural stressors, regional scale impacts, remote sensing imagery, scaling methods, semi-arid environments, survey data, regional, regionalization., RFA, Scientific Discipline, Air, Geographic Area, Ecosystem Protection/Environmental Exposure & Risk, Ecology, Ecosystem/Assessment/Indicators, Ecosystem Protection, Environmental Chemistry, climate change, State, Ecological Effects - Environmental Exposure & Risk, Forestry, Regional/Scaling, Pacific Northwest, anthropogenic stresses, ecological effects, ecological exposure, carbon allocation, semi-arid environments, ecosystem assessment, survey data, Oregon, forest ecosystems, natural stressors, forest inventory and analysis, climate, Washington (WA), ecosystem indicators, regional scale impacts, forests, forest resources, ecosystem stress, remote sensing imagery, ecological response, validation, carbon stress index, scaling methodsProgress and Final Reports:
Original AbstractThe perspectives, information and conclusions conveyed in research project abstracts, progress reports, final reports, journal abstracts and journal publications convey the viewpoints of the principal investigator and may not represent the views and policies of ORD and EPA. Conclusions drawn by the principal investigators have not been reviewed by the Agency.