The global ecosystem has experienced tremendous climate change since the 20th Century.The arid and semi-arid region of Central Asia (referred to as "Central Asia") is one of the most sensitive regions to climate variations.With the intensification of human disturbances such as grazing,the grassland ecosystem in Central Asia has become one of the most uncertain regions in global carbon cycle estimation.Therefore,to accurately evaluate grassland ecosystem productivity,carbon source/carbon sink function and analyze the impact of climate change and human disturbance on the grassland carbon cycle is crucial for grassland resource's reasonable development and effective protection.Ecosystem process-based models are widely used by the researchers to simulate the climate change effects on grassland ecosystem structure and function.The Biome-BGC model,proposed by the Numerical Terradynamic Stimulation Group (NTSG) of Montana University in the United States has been widely used to simulate the spatio-temperal patterns of carbon dynamics in arid areas with limited field data.In this study,we adopted the biogeochemical cycle model Biome-BGC to simulate carbon dynamics in Central Asia for grassland ecosystem.The results indicated as follows:(1) the averaged NPP value of grassland in Central Asia is 135.6 gC·m-2·a-1,which decreased at a rate of 0.34 gC·m-2·a-1. (2) the averaged NPP value of grassland in Central Asia is -8.3 gC·m-2·a-1,acted as a carbon source,which increased at a rate of 0.58 gC·m-2·a-1. (3) NPP high values are mainly presented nearby the Tianshan Mountains and Northern Kazakhstan with relatively abundant rainfall. (4) The interannual variation of NPP is basically consistent with the variation trend of precipitation,the correlation coefficient is 0.52,and the correlation coefficient of NPP and temperature is -0.28,which does not reach significant correlation level.The Biome-BGC model has achieved good simulation results in this area,but uncertainty still exist.The uncertainties mainly come from the following aspects:(1) Biome-BGC is based on the ideal assumption that the vegetation composition remains unchanged,which is not consistent with the reality. (2) It is difficult to accurately parameterize the model because of the lack of reliable field data. (3) The low resolution of the meteorological data.This study proves the usability of Biome-BGC model in grassland ecosystem in arid grasslands of Central Asia.It is of great significance to evaluate the carbon source/sink potential and achieve the sustainable utilization of grassland ecosystem in Central Asia.
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