Simulation of the Carbon Cycle in the Meadow Steppe Dominated by Leymus Chinensis

The Vegetation Interface Processes(VIP) model was used to simulate carbon cycle in the typical steppe dominated by Leymus chinensis in Inner Mongolia.The characteristics of carbon cycle and the relationship between carbon cycle and environmental factors were analyzed.Results showed that the model is successful in simulating variation of the aboveground biomass and net ecosystem production(NEP).Ecosystem primary production and respiration(Re) were decreasing during 1958 to 1973,and then kept increasing until 1993,after that decreased again.Sensitivity analysis showed the carbon cycle variation is more related with precipitation than other environmental factors,and Re is influenced by all the three factors.Increase in the gross primary production(GPP),net primary production(NPP) and Re are attributed mainly to the increasing precipitation and CO2 concentration,the increase in temperature and decrease in precipitation make them decrease.There are great interannual variations of carbon budget during 1958 to 2007 in the study site.There is a close relationship between NEP and precipitations,showing that NEP turns from negative to positive while annual precipitation is greater than 228 mm.