Project Summary:

Models play a prominent role in ecological risk assessments because they are the primary means for relating stressors to probable effects, and for making meaningful extrapolations across scales of time, space, and biological organization. Models are particularly important for risk assessments at the scale of ecosystems because it is exceedingly difficult to experimentally isolate the interactive effects of natural environmental driving forces (temperature, precipitation, cloudiness, etc.) and anthropogenic stressors (e.g., air pollutants, climate change, land use). Process-based models that simulate biogeochemical cycles or forest succession, for example, can help improve such assessments by providing a self-consistent synthesis of the results of many experiments. The synthesis provided by these models includes the interactions among ecosystem processes that give rise to the synergistic responses to multiple factors.

Under PRIMENet, we propose to use the Marine Biological Laboratory's General Ecosystem Model (MBL-GEM) to assess and predict how natural and anthropogenic stressors may affect the health and sustainability of ecosystems in the Olympic National Park. The MBL-GEM is a process-based model of ecosystem carbon (C) and nitrogen (N) dynamics that simulates the effects of changes in atmospheric CO₂ concentration, temperature, precipitation, irradiance, and N deposition on plant and soil processes. Processes in the model include photosynthesis, respiration, tissue growth, N retranslocation, litterfall, decomposition, soil N dynamics, and soil-plant-atmosphere hydrology. The MBL-GEM is intended to be generally applicable to most terrestrial ecosystems and has been used in the past to analyze the biogeochemical responses of temperate deciduous forests, tropical evergreen forests, and arctic tundra to changes in atmospheric CO₂ concentration, N deposition, temperature, irradiance (cloudiness), and soil moisture. In addition, the EPA has recently parameterized MBL-GEM for forest ecosystems located along an elevational gradient in the South Santiam watershed in the western Cascades of Oregon, a first step toward the development of a regionally robust parameterization for Pacific Northwest forests.

Our primary objective is to develop a parameterization of MBL-GEM that can be used as a risk assessment tool for ecosystems in the Olympic National Park and in the Pacific Northwest in general. Specifically, we will use MBL-GEM to:

	Assess and predict future responses of forest ecosystems to natural and anthropogenic stressors, including changes in temperature, precipitation, cloudiness (light), CO2, ozone, and N deposition
	Link changes in condition to likely stressors
	Identify efficient and sensitive indicators (early warning measures) for loss of ecosystem integrity and sustainability

To accomplish these objectives we propose to carry out two primary activities under PRIMENet:

	Collect biogeochemical and meteorological data at four sites in the Olympic National Park selected based on forest species, elevation, climate and fertility to evaluate the regional applicability of MBL-GEM
	Make improvements to MBL-GEM to better address risk assessment issues of interest to the EPA, e.g. tropospheric ozone exposure and nitrogen deposition

A major product of PRIMENet will be to produce a well-validated, single parameter set of MBL-GEM that can be applied with confidence to all major forest types, soils and climatic conditions within the Pacific Northwest, enabling credible, spatially explicit predictions of environmental stressor effects.

 

Final Report

2002 Olympic PRIMENet Meeting Presentation

 

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