The main technical objectives of RC-201703 are to (1) evaluate the performance of five extant ecosystem process models simultaneously at 3-5 sites across the country, and (2) select and apply, after the model evaluation phase, the most appropriate model(s) to meet the modeling needs of resource managers at selected demonstration sites (i.e., the demonstration phase).

Phase 1: Model Performance Evaluation. The purpose of Phase I is to objectively evaluate the performance of five ecosystem models at 3-5 sites across the country. The sites include two forest research sites identified by the Environmental Security Technology Certification Program (ESTCP) and 1-3 additional flux tower sites in a global network of micrometeorological tower sites that use eddy covariance methods to measure carbon, energy, and water fluxes between ecosystems and the atmosphere (FLUXNET) and a regional network of tower sites that use eddy covariance methods to measure carbon, energy, and water fluxes between land and the atmosphere in the United States (AmeriFlux) systems. There are two main tasks in this phase. First, to represent the diversity and the state-of-the-art of ecosystem modeling and maintain consistency in intercomparison. To do this, researchers will select and add five well-established ecosystem models into the General Ensemble Biogeochemical Modeling System (GEMS) framework. Second, researchers will use four statistical metrics to assess the performance of each of these models in characterizing (1) carbon pools and fluxes, (2) impacts of natural disturbances and management activities, (3) effects of changes in climate, (4) vegetation and soil dynamics, and (5) nitrogen dynamics at various sites and time steps (e.g., daily, monthly, annual, and decadal). Models will also be assessed qualitatively on structure, particularly regarding their ability to simulate the impacts of land use and climate change, model parameter sensitivity, and uncertainty.

Phase 2: Model Demonstration. In this phase researchers will work closely with Department of Defense (DoD) resource managers and technical staff to demonstrate the value of the results from this study, including model selection and applications to address management decisions on specific DoD installations. Demonstrations will be done at both plot and regional scales. Plot-scale demonstration will use case studies to show the impacts of management practices on ecosystems. For regional applications, GEMS will be deployed to simulate ecosystem dynamics spatially at 30-meter resolution.

Model intercomparisons can assist managers in the appropriate selection and use of models by uncovering the strengths and weaknesses, appropriate uses, and user friendliness of individual models. The proposed project will produce a comprehensive assessment of the performance of the state-of-the-art ecosystem models in simulating ecosystem dynamics (e.g., carbon stocks and fluxes) in response to disturbances, management, and climate change. The DoD resource managers can select the best or the best set of models for operational purposes according to their circumstances to quantify the plausible consequences of various driving forces on ecosystem change so that they can make informed adaptive management decisions.