HR: 0800h
AN: B31A-02    [Abstracts]
TI: A Hierarchical Analysis of the Temrrestrial Ecosystem Model Biome-BGC
AU: * Wang, W
EM: weile.wang@gmail.com
AF: California State University, Monterey Bay, 100 Campus Center, Building 201, Suite 109, Seaside, CA 93955, United States
AU: * Wang, W
EM: weile.wang@gmail.com
AF: NASA Ames Research Center, Mail Stop 242-4, NASA Ames Research Center, Moffett Field, CA 94035, United States
AU: Ichii, K
EM: kichii@arc.nasa.gov
AF: San Jose State University, One Washington Square, San Jose, CA 95192, United States
AU: Hashimoto, H
EM: hirofumi.hashimoto@gmail.com
AF: California State University, Monterey Bay, 100 Campus Center, Building 201, Suite 109, Seaside, CA 93955, United States
AU: Hashimoto, H
EM: hirofumi.hashimoto@gmail.com
AF: NASA Ames Research Center, Mail Stop 242-4, NASA Ames Research Center, Moffett Field, CA 94035, United States
AU: Nemani, R R
EM: ramakrishna.r.nemani@nasa.gov
AF: NASA Ames Research Center, Mail Stop 242-4, NASA Ames Research Center, Moffett Field, CA 94035, United States
AB: The increasing complexity of ecosystem models represents a major difficulty in calibrating model parameters and analyzing simulated results. To address this problem, this study develops a hierarchical scheme that simplifies the Biome-BGC model into three functionally cascaded layers and analyzes them sequentially. The first-layer model focuses on leaf-level ecophysiological processes. With prescribed leaf area index (LAI) for the canopy, this layer of model can be relatively easily calibrated to simulate observed fluxes of evapotranspiration (ET) and photosynthesis (gross primary production, GPP). The second-layer model considers the carbon/nitrogen cycles within the simulated vegetation under equilibrium conditions. Based on the principle of carbon balance, it estimates biomass storage in various vegetation components and their demands for annual carbon allocation directly from the observed LAI and the allocation scheme described in Biome-BGC. The nitrogen content of vegetation components and their requirement for soil nitrogen uptake are subsequently determined. The third-layer model extends the methodology of the second layer to analyze carbon/nitrogen balances in all litter/soil pools. In particular, it estimates the nitrogen fluxes from soil and litter to the atmosphere, and finally determines annual nitrogen input that satisfies the total nitrogen balance of the simulated ecosystem. This model hierarchy is examined with model experiments for four Ameri-Flux sites, and the simulated results are consistent with theoretically estimations. Therefore, the hierarchical scheme developed in this study can serve as a practical guide for calibrating or/and analyzing Biome-BGC. In addition, it may be helpful to analyze other similar ecosystem models as well.
DE: 0414 Biogeochemical cycles, processes, and modeling (0412, 0793, 1615, 4805, 4912)
DE: 0428 Carbon cycling (4806)
DE: 0439 Ecosystems, structure and dynamics (4815)
DE: 0466 Modeling
DE: 0469 Nitrogen cycling
SC: Biogeosciences [B]
MN: 2007 Joint Assembly