PARENT SESSION
Poster Session #12: Modeling.
Tuesday, August 7, 2001. Presentation from 10:30 AM to 12:00 PM. Exhibition Hall
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Modeling of forest/atmosphere carbon fluxes in a Colorado subalpine ecosystem.
Le Dantec, Valerie1, Luo, Yiqi1, Turnipseed, Andrew2, Sparks, Jed2, Harley, Peter2, Monson, Russel2, 1 2
ABSTRACT- The primary objective of this study is to use a process-based model to predict Net Ecosystem Exchange (NEE) in a subalpine coniferous forest and to partition NEE into different components. Ecosystem CO2 and H2O fluxes have been measured continuously above an even-aged coniferous stand at Niwot Ridge (Colorado) using an eddy-covariance instrument since 1999. We applied a soil-plant forest ecosystem model, CASTANEA (developed by E. Dufrene), to predict carbon and water fluxes at the site in 1999 and 2000 as functions of weather data and stand characteristics. We have parameterized the model using measurements at the leaf level (photosynthesis, stomatal conductance, nitrogen content and leaf mass per area) and the stand level (species composition, plant biomass, leaf area index, soil carbon content). The main output variables are canopy photosynthesis and transpiration, maintenance and growth respirations, evapotranspiration at half-hour time step and plant biomass growth, soil respiration and water content at daily time step. We tested the model against eddy flux data and additional ecological measurements such as soil and bole respirations, sapflow and soil water content. In general, the model well reproduces seasonal variability of NEE in that subalpine coniferous stand. We used the model to evaluate differential influences of environmental and biological factors on the two major components (respiration and photosynthesis) of NEE. Our modeling study has identified some of the key factors that control seasonal variability in NEE.
KEY WORDS: modeling, Net Ecosystem Exchange, subalpine forest, seasonal variability