Integrated land-surface hydrological and biogeochemical processes in simulating water, energy and carbon fluxes over two different ecosystems

Abstract

Understanding the mechanism of the interactions between vegetation dynamics and the water cycle is rather important for determining global and regional water and carbon budgets. In this paper, a physically-based model integrating land-surface hydrological and biogeochemical processes by coupling a hydrological model and a biogeochemical model is developed to simulate the water, energy and carbon fluxes. The model is validated against observed biometric, eddy-covariance flux, soil moisture and temperature data over two different ecosystems. Results show that the model could simulate the vegetation physiological and hydrological processes satisfactorily including net radiation, latent heat, gross primary production (GPP), net ecosystem exchange and soil moisture and temperature. Sensitivity analysis illustrates that evapotranspiration, GPP, net ecosystem production are quite sensitive to plant physiological controls such as the maximum electron transport rate, quantum efficiency of electron transport and runoff parameter. Moreover, results show that a close relationship between photosynthesis and transpiration. Water use efficiency shows a U-bend curve at different time steps and it also indicates a higher value in forest ecosystem than that of grass ecosystem. In the forest ecosystem, evapotranspiration is higher and the surface runoff is lower. Meanwhile it is almost carbon sink during the whole year, while in the grass ecosystem, it shows a carbon source during May to September. This study could provide an effective model for the simulation of water-carbon cycles.