A terrestrial biogeochemical model （CASACNP） was coupled to a land surface model （the Common Land Model,CoLM） to simulate the dynamics of carbon substrate in soil and its limitation on soil respiration.The combine...A terrestrial biogeochemical model （CASACNP） was coupled to a land surface model （the Common Land Model,CoLM） to simulate the dynamics of carbon substrate in soil and its limitation on soil respiration.The combined model,CoLM CASACNP,was able to predict long-term carbon sources and sinks that CoLM alone could not.The coupled model was tested using measurements of belowground respiration and surface fluxes from two forest ecosystems.The combined model simulated reasonably well the diurnal and seasonal variations of net ecosystem carbon exchange,as well as seasonal variation in the soil respiration rate of both the forest sites chosen for this study.However,the agreement between model simulations and actual measurements was poorer under dry conditions.The model should be tested against more measurements before being applied globally to investigate the feedbacks between the carbon cycle and climate change.展开更多
Soil moisture has a significant influence on water, energy, and carbon biogeochemical cycles. A numerical method for solving Richards＇ equation is usually used for simulating soil moisture. Selection of a lower bound...Soil moisture has a significant influence on water, energy, and carbon biogeochemical cycles. A numerical method for solving Richards＇ equation is usually used for simulating soil moisture. Selection of a lower boundary condition for Richards＇ equation will further affect the simulation results for soil moisture, water cycle, energy balance, and carbon biogeochemical processes. In this study, the soil water movement dynamic sub-model of a hydrologically based land surface model, the variable infiltration capacity （VIC） model, was modified using the finite difference method （FDM） to solve a mixed form of Richards＇ equation. In addition, the VIC model was coupled with a terrestrial biogeochemical model, the Carnegie Ames Stanford Approach model of carbon, nitrogen, and phosphorus （CASACNP model）. The no-flux boundary （NB） and free-drainage boundary （FB） were selected to investigate their impacts on simulations of the water, energy, and soil carbon cycles based on the coupling model. The NB and FB had different influences on the water, energy, and soil carbon simulations. The water and energy simulations were more sensitive, while the soil carbon simulation was less sensitive to FB than to NB. Free-drainage boundary could result in lower soil moisture, evaporation, runoff, and heterotrophic respiration and higher surface soil temperature, sensible heat flux, and soil carbon content. The impact of the lower boundary condition on simulation would be greater with an increase in soil permeability. In the silt loam soil case, evaporation, runoff, and soil respiration of FB were nearly 169, 13%, and 1% smaller, respectively, compared to those of NB.展开更多
基金supported by R & D Special Fund for Nonprofit Industry (Meteorology,GYHY200706025),the U.S. Department of Energy,Office of Science,Biological and Environmental ResearchOak Ridge National Laboratory is managed by UT-Battelle,LLC for the U.S. Department of Energy under Contract No. DE-AC05-00OR22725
文摘A terrestrial biogeochemical model （CASACNP） was coupled to a land surface model （the Common Land Model,CoLM） to simulate the dynamics of carbon substrate in soil and its limitation on soil respiration.The combined model,CoLM CASACNP,was able to predict long-term carbon sources and sinks that CoLM alone could not.The coupled model was tested using measurements of belowground respiration and surface fluxes from two forest ecosystems.The combined model simulated reasonably well the diurnal and seasonal variations of net ecosystem carbon exchange,as well as seasonal variation in the soil respiration rate of both the forest sites chosen for this study.However,the agreement between model simulations and actual measurements was poorer under dry conditions.The model should be tested against more measurements before being applied globally to investigate the feedbacks between the carbon cycle and climate change.
基金supported by the National Science Foundation for Distinguished Young Scholars of China (No. 51309245)supported by the US Department of Energy and National Aeronautics and Space Administration
文摘Soil moisture has a significant influence on water, energy, and carbon biogeochemical cycles. A numerical method for solving Richards＇ equation is usually used for simulating soil moisture. Selection of a lower boundary condition for Richards＇ equation will further affect the simulation results for soil moisture, water cycle, energy balance, and carbon biogeochemical processes. In this study, the soil water movement dynamic sub-model of a hydrologically based land surface model, the variable infiltration capacity （VIC） model, was modified using the finite difference method （FDM） to solve a mixed form of Richards＇ equation. In addition, the VIC model was coupled with a terrestrial biogeochemical model, the Carnegie Ames Stanford Approach model of carbon, nitrogen, and phosphorus （CASACNP model）. The no-flux boundary （NB） and free-drainage boundary （FB） were selected to investigate their impacts on simulations of the water, energy, and soil carbon cycles based on the coupling model. The NB and FB had different influences on the water, energy, and soil carbon simulations. The water and energy simulations were more sensitive, while the soil carbon simulation was less sensitive to FB than to NB. Free-drainage boundary could result in lower soil moisture, evaporation, runoff, and heterotrophic respiration and higher surface soil temperature, sensible heat flux, and soil carbon content. The impact of the lower boundary condition on simulation would be greater with an increase in soil permeability. In the silt loam soil case, evaporation, runoff, and soil respiration of FB were nearly 169, 13%, and 1% smaller, respectively, compared to those of NB.
