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Final 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: R828309
Title: Regional Analysis of Net Ecosystem Productivity of Pacific Northwest Forests: Scaling Methods, Validation and Results Across Major Forest Types and Age Classes
Investigators:
Institution:
EPA Project Officer: Smith, Bernice
Project Period: July 1, 2000 through June 30, 2003 (Extended to June 30, 2004)
Project Amount: $1,848,927
RFA: Regional Scale Analysis and Assessment (1999)
Research Category: Ecological Indicators/Assessment/Restoration

Description:

Objective:

The objectives of this research project were 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 (NEP) are influenced by forest development, disturbances, and contrasting climatic conditions.

Summary/Accomplishments (Outputs/Outcomes):

We developed and tested our scaling approach (Objective 1) using a spatially nested hierarchy of field and remote sensing observations to develop model parameters (e.g., foliar nitrogen) and controlling variables (e.g., maximum leaf area) and to test model output. The field design included: intensive sites of chronosequences along the climatic gradient to determine the magnitude of the effect of disturbance on carbon stocks and fluxes in different climate zones or ecoregions; extensive sites to develop remote sensing algorithms for maximum leaf area, forest age, and land cover; and inventories for testing remote sensing estimates of cover and age and for testing model predictions of productivity. The approach yielded estimates of regional C stocks and flux that were in agreement with the field observations (Law, et al., 2004, 2005).

Examination of carbon allocation patterns in the field (Campbell, et al., 2005) and as suggested by forest inventory data (Law, et al., 2004; Van Tuyl, et al., 2005) revealed that carbon allocation to above and below ground plant organs is dynamic with forest age, and the allocation patterns differ by ecoregion/climate zone. The dynamic carbon allocation parameterization with forest age that we developed for the Biome-Biogeochemical Cycles (BGC) model should be applied by ecoregion using inventory data. (We had applied only two parameterization schemes, and we need to improve these with further analysis of the inventory data.)

The findings of this study indicate that we need to better quantify dead carbon pools, as well as rates of tree mortality, and incorporate this knowledge in the Biome-BGC model to improve predictions of heterotrophic respiration. (NEP is the net of net primary productivity (NPP) and heterotrophic respiration.) We also learned that we should know the thinning history of forests spatially to properly parameterize the model for soil water availability. (Maximum leaf area index [LAI] from remote sensing data was used to set the soil water holding capacity, but the observed LAI can be below the potential of a site if the forest was thinned.) This will be an area of future modeling and remote sensing improvements.

We used a spatially nested hierarchy of field and remote sensing observations and a process model, Biome-BGC, to produce a carbon budget for the forested region of Oregon and to determine the relative influence of differences in climate and disturbance among the ecoregions on carbon stocks and fluxes. The simulations suggest that annual net uptake (NEP) for the whole forested region (8.2 million hectares) was 13.8 Tg C (168 g C m-2 yr-1), with the highest mean uptake in the mesic Coast Range ecoregion (226 g C m-2 yr-1) and the lowest mean NEP in the semi-arid East Cascades ecoregion (88 g C m-2 yr-1). Carbon stocks totaled 2765 Tg C (33,700 g C m-2), with wide variability among ecoregions in the mean stock and in the partitioning above and below ground. The flux of carbon from the land to the atmosphere that is driven by wild fire was relatively low during the late 1990s (~0.1 Tg C yr-1), however, wildfires of historic proportions in 2002 generated a much larger C source (~2.5 Tg C). Annual harvest removals from the study area over the 1995-2000 period were approximately 5.5 Tg C yr-1, or twice that of carbon losses from the historic fires. Net biome production (NBP) on the land—the net effect of NEP, harvest removals, and wildfire emissions—indicate the study area was a sink over 1995-2000 (8.2 Tg C yr-1). NBP of the study area, which is the more heavily forested half of the state, compensated for approximately 52 percent of Oregon’s fossil carbon dioxide emissions of 15.6 Tg C yr-1 in 2000, much higher than the national average of 20 percent compensation. The regional total reflects the strong east-west gradient in potential productivity associated with the climatic gradient and a disturbance regime that has been dominated in recent decades by commercial forestry (Law, et al., 2004).

NEP in 3 climatically distinct chronosequences was very negative (a source to the atmosphere) immediately following stand replacing disturbance in all forests and recovered to positive values by 10, 20, and 30 years of age for the mild and mesic Coast Range, mesic West Cascades, and semi-arid East Cascades, respectively. The response of stand-level NEP to individual disturbance events is greater than that attributable to edaphoclimatic differences between forest types. Regional age class distributions, however, are such that the variability in landscape-level NEP attributable to disturbance regimes is equivalent to that attributable to regional edaphoclimatic differences between forest types (Campbell, et al., 2005a).

Data from our 96 plots that represent the range of forest types in the Pacific Northwest United States showed that the relative contribution of soil and detritus carbon to total ecosystem carbon decreased as a negative exponential function of stand age to a value of approximately 35 percent between 150-200 years across the forest types. These age-dependent trends in the portioning of carbon between biomass and necromass were not different among forest types. Model estimates of soil carbon storage based on decomposition of legacy carbon and carbon accumulation following stand-replacing disturbance showed that soil carbon storage became steady between 150-200 years, which has significant implications to modeling carbon dynamics of the temperate coniferous forests following a stand replacing disturbance. This information on soil carbon was used to evaluate our ecosystem process model estimates of soil carbon on the plots and we found that standard parameterizations for soil C resulted in significant differences in the coastal region compared with field observations (Sun, et al., 2004).

Inventory data generally are quite limited to estimates of bolewood volume and above ground merchantable wood. We used a novel approach that leveraged these data by developing models from our extensive and intensive plot data to estimate NPP at approximately 5,000 plots across the region. We found that forest age distributions differed by geographic location with fewer old stands in the Coast Range and the East Cascades and a relatively uniform distribution of ages from 0 to 815 in the Cascade Mountains. Age distributions also differed by land ownership, with fewer old stands on non-federal lands than on national forest lands. The timing and magnitude of maximum NPP varied by ecoregion, with the high productivity Coast Range forests reaching a median NPP approximately 1 kg C m-2 y-1 before 30 years of age and the low productivity East Cascades reaching a median NPP approximately 0.25 kg C m-2 y-1 between 80 and 100 years. Productivity generally was lower in older stands in all areas except for the Eastern Cascades, contrary to the paradigm of age-related decline in forest growth (Van Tuyl, et al., 2005).

The regional modeling of land feedbacks to the atmosphere (net emissions) in Law, et al. (2004) pointed out the lack of information in the region on emissions from wildfires. In 2004, an analysis of the effects of logging and wildfire on carbon emissions and transformations on the ground was conducted in the historic Biscuit Fire region (200,000 ha) to reduce uncertainty in regional estimates of land-based carbon uptake. Preliminary results suggest that carbon emissions from wildfire are not as large as previous studies suggested in other regions (Campbell, et al., in preparation).

In our initial simulation of the carbon balance of western Oregon (Law, et al., 2004), we generally did not differentiate between different stand origins (e.g., between stands originating after fires versus clearcuts). Our recent observations at the Biscuit Fire region suggest that considerably more woody debris residue is left after a fire than after a clearcut, and we are now incorporating that information in a new analysis of NBP (NBP = net of carbon uptake by terrestrial systems, NEP, minus losses from logging and wildfire) in western Oregon. Our earlier model simulations in the point mode and spatial mode (Turner, et al., 2003) also found considerable interannual variation in NPP and heterotrophic respiration, hence, in NEP. In the new analysis of western Oregon, we now are simulating the period 1980-2003 and are assembling annual regional estimates of NEP to evaluate the sensitivity of the regional C flux to interannual climate variability.

Conclusions:

We developed a regional scale approach to quantify the carbon balance of terrestrial ecosystems across regions, based on a spatially nested hierarchy of field and remote sensing observations: intensive flux sites where process level studies are conducted to understand mechanisms controlling carbon fluxes, intermediate plots in scope of measurements and spatial frequency that are used to develop remote sensing algorithms and to supplement inventory data for calculations of NPP, forest inventories, and the optical remote sensing. The measurements ultimately are used to parameterize and drive an ecosystem process model. Carbon stocks in vegetation and soils are mapped, as well as the net annual carbon uptake, to understand the influence of climate and disturbance on changes in carbon sequestration by terrestrial ecosystems.

The conceptual approach of using a spatially nested hierarchy of remote sensing and field observations for data-driven bottom-up modeling of carbon stocks and fluxes has been adopted by the multi-agency North American Carbon Program (NACP), which is part of the U.S. Carbon Cycle Science Program (USCCSP), is a component of the Climate Change Science Program launched in 2002. Dr. Law is on the Science Steering Group of the USCCSP and the NACP, as well as a contributing author of this observation-driven modeling paradigm to the Implementation Strategy of the NACP. There are about eight federal agencies involved in the USCCSP and NACP, including the U.S. Environmental Protection Agency.

Regional carbon budgets can be produced with reduced uncertainty for the NACP and the annual State of the Carbon Cycle Report (SoCCR) that is a required product of the Climate Change Science Program. Dr. Law’s group now is applying this approach in an NACP project that covers Oregon and Northern California and will produce regional carbon balance estimates for the NACP and SoCCR. They also will provide an evaluation of the effect of forest management (thinning, clear-cut logging) and wildfire on carbon emissions from terrestrial systems and carbon sequestration relative to fossil fuel emissions in the region. Ultimately, the plan is to use more sophisticated data assimilation techniques to incorporate measurements in models to reduce uncertainty in quantifying the role of terrestrial ecosystems in the global carbon cycle.


Journal Articles on this Report : 14 Displayed | Download in RIS Format

Other project views: All 35 publications 23 publications in selected types All 22 journal articles

Type Citation Project Document Sources
Journal Article Campbell JL, Sun O, Law BE. Disturbance and net ecosystem production across three climatically distinct forest landscapes. Global Biogeochemical Cycles 2004;18:GB4017, doi: 10.1029/2004GB002236.
abstract available  
R828309 (Final)
  • Abstract: AGU
    Exit
  • Journal Article Campbell JL, Sun OJ, Law BE. Supply-side controls on soil respiration among Oregon forests. Global Change Biology 2004;10(11):1857-1869.
    abstract available  
    R828309 (2000)
    R828309 (2001)
    R828309 (2002)
    R828309 (Final)
  • Abstract:
    Exit
  • Journal Article Campbell JL, Law BE. Forest soil respiration across three climatically distinct chronoseqeunces in Oregon. Biogeochemistry 2005;73(1):109-125.
    abstract available  
    R828309 (Final)
  • Abstract: SpringerLink
    Exit
  • Journal Article Cohen WB, Maiersperger TK, Spies TA, Oetter DR. Modelling forest cover attributes as continuous variables in a regional context with Thematic Mapper data. International Journal of Remote Sensing 2001;22(12):2279-2310.
    abstract available  
    R828309 (2000)
    R828309 (2001)
    R828309 (Final)
  • Abstract: Informa World
    Exit
  • Journal Article 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.
    abstract available  
    R828309 (2000)
    R828309 (2001)
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    R828309 (Final)
  • Abstract: Springerlink
    Exit
  • Journal Article 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.
    abstract available   full text available
    R828309 (2002)
    R828309 (Final)
  • Full-text: Science Direct
    Exit
  • Abstract: Science Direct
    Exit
  • Other: Science Direct
    Exit
  • Journal Article Lefsky MA, Cohen WB, Spies TA. An evaluation of alternate remote sensing products for forest inventory, monitoring, and mapping of Douglas-fir forests in western Oregon. Canadian Journal of Forest Research 2001;31(1):78-87.
    abstract available  
    R828309 (2000)
    R828309 (2001)
    R828309 (Final)
  • Abstract: NRC Research Press
    Exit
  • Journal Article Lefsky MA, Turner DP, Guzy M, Cohen WB. Combining lidar estimates of aboveground biomass and Landsat estimates of stand age for spatially extensive validation of modeled forest productivity. Remote Sensing of Environment 2005;95(4):549-558.
    abstract available   full text available
    R828309 (Final)
  • Full-text: Science Direct
    Exit
  • Abstract: Science Direct
    Exit
  • Other: Science Direct PDF
    Exit
  • Journal Article 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.
    abstract available  
    R828309 (2000)
    R828309 (2001)
    R828309 (2002)
    R828309 (Final)
  • Abstract: Wiley Interscience
    Exit
  • Journal Article 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.
    abstract available  
    R828309 (2002)
    R828309 (Final)
  • Abstract: Wiley Interscience
    Exit
  • Journal Article Turner DP, Ollinger SV, Kimball JS. Integrating remote sensing and ecosystem process models for landscape- to regional-scale analysis of the carbon cycle. BioScience 2004;54(6):573-584.
    abstract available  
    R828309 (Final)
  • Abstract: BioOne
    Exit
  • Journal Article 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.
    abstract available   full text available
    R828309 (2002)
    R828309 (Final)
  • Abstract from PubMed
  • Full-text: Oregon State University PDF
    Exit
  • Journal Article Van Tuyl S, Law BE, Turner DP, Gitelman AI. Variability in net primary production and carbon storage in biomass across Oregon forests--an assessment integrating data from forest inventories, intensive sites, and remote sensing. Forest Ecology and Management 2005;209(3):273-291.
    abstract available   full text available
    R828309 (Final)
  • Full-text: Science Direct
    Exit
  • Abstract: Science Direct
    Exit
  • Other: Science Direct
    Exit
  • Journal Article Woodcock CE, Macomber SA, Pax-Lenney M, Cohen WB. Monitoring large areas for forest change using Landsat: generalization across space, time and Landsat sensors. Remote Sensing of Environment 2001;78(1-2):194-203, Special Issue.
    abstract available   full text available
    R828309 (Final)
  • Full-text: Science Direct
    Exit
  • Abstract: Science Direct
    Exit
  • Other: Science Direct
    Exit
  • Supplemental Keywords:

    Pacific Northwest forests, net ecosystem production, NEP, tree mortality, forest inventories, carbon flux scaling, carbon accumulation, bolewood, carbon fluxes, remote scaling, ecosystem assessment, forest inventory and analysis, remote sensing imagery, scaling methods, survey data,, RFA, Scientific Discipline, Air, Geographic Area, Ecosystem Protection/Environmental Exposure & Risk, Ecology, Environmental Chemistry, Ecosystem/Assessment/Indicators, Ecosystem Protection, climate change, State, Forestry, Ecological Effects - Environmental Exposure & Risk, Regional/Scaling, Pacific Northwest, anthropogenic stresses, carbon allocation, ecological effects, semi-arid environments, ecological exposure, ecosystem assessment, Oregon, survey data, forest inventory and analysis, forest ecosystems, climate, natural stressors, Washington (WA), regional scale impacts, ecosystem indicators, forests, remote sensing imagery, ecosystem stress, forest resources, ecological response, validation, OR, carbon stress index

    Progress and Final Reports:
    Original Abstract
    2000 Progress Report
    2001 Progress Report
    2002 Progress Report

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    The 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.

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