HR: 09:30h
AN: B21B-07    [Abstracts]
TI: Modeling Radiation and Photosynthesis of a Heterogeneous Savanna Woodland Landscape with a Hierarchy of Model Complexity
AU: * Chen, Q
EM: qichen@hawaii.edu
AF: University of Hawaii at Manoa, Department of Geography, University of Hawai`i at Manoa, 422 Saunders Hall, 2424 Maile Way, Honolulu, HI 96822, United States
AU: Baldocchi, D
EM: baldocchi@nature.berkeley.edu
AF: University of California, Berkeley, Department of Environmental Science, Policy, and Management, 137 Mulford Hall, University of California at Berkeley, Berkeley, CA 94720, United States
AB: Simple but realistic modeling of radiation transfer within heterogeneous canopy has been a challenging research question for decades and is critical for predicting ecological processes such as photosynthesis. The Markov model proposed by Nilson (1971) is theoretically sound to meet this challenge. However, it has not been widely used because of the difficulty of determining the clumping factor. We propose an analytical approach to calculate clumping factors based on the average characteristics of vegetation distributed across a landscape. In a savanna woodland in California, we simulate the photosynthesis of the landscape in three different ways: 1) the crown envelope and location of each tree is spatially-explicitly specified, 2) the canopy is assumed to be horizontally homogeneous within which leaves are randomly dispersed as a Poisson process, and 3) the canopy is horizontally homogeneous but leaves are clumped and distributed with a Markov process. We find that the Markov model can achieve much better performance than the Poisson model. Incorporating the clumping factor can reduce the percent error of CO2 assimilation estimation significantly (e.g., from around 50% to 10% when local leaf area index is 4.5 m2/m2). The results indicate that our approach of calculating clumping factors has applications in terrestrial ecosystem modeling, particularly where accurate representation of "system heterogeneity" (e.g., savannas and woodlands) is required.
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: 0480 Remote sensing
SC: Biogeosciences [B]
MN: 2007 Fall Meeting