PARENT SESSION
Oral Session # 28: Ecological Modeling II.
Presiding: R Park
Tuesday, August 5. 1:30 PM to 5:00 PM, SITCC Meeting Room 102.
Carbon and water cycle simulations for an upland oak forest from 1993 to 2000 using 13 stand-level models: Intermodel comparisons and evaluations against independent measurements.
Hanson, Paul1, Others, 172, 1 Environmental Sciences Division, Oak Ridge, TN, USA2 Various Institutions, USA, Canada, and UK
ABSTRACT- Models represent our primary method for integration of small-scale, process-level phenomenon into a cohesive description of forest-stand or ecosystem function. They also represent our only viable means for testing hypotheses about the response of forest ecosystems to changing environmental conditions. This poster summarizes the evaluation of 13 stand-level models varying in their spatial, mechanistic, and temporal complexity for their ability to capture intra- and inter-annual components of the water and carbon cycle for an upland, oak-dominated forest of eastern Tennessee. Comparisons between model simulations and observations were done for hourly, daily and annual time steps. Response surfaces of carbon and water flux as a function of environmental drivers, and a variety of goodness-of-fit statistics were used to judge model performance. A single model did not consistently perform the best at all time steps. Not surprisingly, those models missing key forest components or processes (e.g., soil water content) were unable to provide accurate predictions of ecosystem responses to short-term drought phenomenon. An inability to correctly capture physiological processes under drought, however, was not necessarily an indicator of poor long-term water and carbon budget simulations. This is possible because droughts in the subject ecosystem were of short duration over the 1993 to 2000 period, and therefore had a small cumulative impact. Models using hourly time steps, based on mechanistic processes, and having a realistic spatial representation of the forest ecosystem provided the best predictions of observed data. Models designed for wide application to a range of ecosystems performed poorly in this comparison, suggesting the need for continued evaluation and improvement of ecosystem models targeted for extrapolation to broad geographic regions. Co-authors: J.S. Amthor, S.D. Wullschleger, K.B. Wilson, R.F. Grant, A. Hartley, D. Hui, E.R. Hunt Jr., D.W. Johnson, J. Kimball, A.W. King, Y. Luo, S.G McNulty, G. Sun, P.E. Thornton, S. Wang, M. Williams, and R.M. Cushman.
Key words: water modeling, ecosystem , carbon modeling, Oak forest