Modeling Canopy Carbon and Water Fluxes Using a Multilayered Model over a Temperate Meadow in Inner Mongolia

Abstract

To incorporate canopy vertical structure in a process-based model over a temperate meadow, a multilayered model estimated canopy carbon flux ( F c ) and water flux ( LE ) was applied by comparing with eddy covariance measurements in Inner Mongolia, China. Simulations of diurnal, seasonal CO 2 and H 2 O fluxes and model sensitivity to parameters and variables were analyzed. The results showed that the model underestimated F c and LE by about 0.6% and 5.0%, respectively. It was able to simulate the diurnal and seasonal variation of F c and LE and performed well during the day and in the growing season, but poorly at night and early in the growing season. F c was more sensitive to the leaf nitrogen content distribution coefficient and maximum catalytic activity of Rubisco, whereas LE showed greater sensitivity to the stomatal conductance parameter a 1 , empirical coefficient of stomatal response to saturated vapor pressure difference V pds0 , and minimum stomatal conductance of CO 2 g sc0 . The response of F c to environmental factors was ranked as air CO 2 concentration ( C a ) > air temperature ( T a ) > photosynthetically active radiation (PAR) > soil water content ( θ sm ) > vapor pressure deficit (VPD) > wind speed ( u 0 ). The response of LE to environmental factors was ranked as T a > VPD > θ sm > PAR> C a > u 0 . The response of LE to vegetation characteristic parameters was greater than that of F c .

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