Effects Of Land Use Change On Terrestrial Vegetation Carbon Uptake In China During 2000—2013

Climate change and climate disasters were caused by the warming effect,but eventually due to the rise of atmospheric carbon dioxide concentration.As the source and sink of atmospheric CO₂,terrestrial ecosystem carbon cycle is an important link in the global carbon cycle and plays an important role in the global climate change.In the process of terrestrial ecosystem carbon cycle,Land use/cover change is an important factor which affects terrestrial ecosystem carbon cycle and influences the regional carbon budget.Thus,it is of great significance to study the effect of land use/cover change on terrestrial carbon budget.In this study,we simulated the Net Ecosystem Productivity?NEP?using the C-FIX model with NDVI,air temperature,and land surface radiation,Spatio-temporal patterns of terrestrial vegetation carbon sink in China were finally examined in 2000—2013.The results showed:?1?The total annual carbon uptake of terrestrial vegetation in China was2.252PgC/a,and reveals a statistically significant increasing trend at a rate of0.031PgC/a?P<0.01?.?2?Spatial patterns of carbon uptake in China have a decreasing trend from south to north and from east to west,with high sinks occurring in Yunnan,Inner Mongolia,Sichuan,HeiLongjiang and Guangxi provinces.All provinces in China except Heilongjiang show a statistically increasing trend of carbon uptake.?3?China's terrestrial vegetation characterized carbon sinks in all seasons during the period 2000—2013.Annual increase of carbon uptake is statistically significant in all seasons except winter.Total carbon uptake is highest in summer?seven times more than that in winter?and decreases in autumn,spring and winter,respectively.?4?Our control experiments suggest that vegetation change is the largest influencing factor in elevated carbon uptake in China,which accounts for 54.875%of total change.Increases in atmospheric CO₂ and climate change contribute about 22.449%and 22.676%,respectively.Vegetation change is the main factor that leads to the increase of carbon uptake.?5?China's land use has changed obviously during 2000—2013.The woodland area increased largest among increasing area which enlarged 286670 square kilometers,construction land and territorial waters increase smaller which enlarged 38690 and24980 square kilometers,respectively;The unused land area dcreased most which reduced 153750 square kilometers,cultivated land and grassland dcreased lessly which reduced 121810 and 8850 square kilometers,respectively.Unused land to forest,grassland and cultivated land to forest,grassland is the main factor causing the terrestrial vegetation carbon uptake increased,Unused land to forest,grassland which makes terrestrial vegetation carbon uptake increased 291.727TgC;Cultivated land to forest,grassland which makes regional carbon uptake increased 314.412TgC.Resulting from land use change which indicates the“grain for green”policy plays an important role in regulating the vegetation carbon uptake of our country.?6?The twelve provinces in China,which terrestrial vegetation carbon uptake significantly change,their land use have changed obviously during 2000—2013.The main land use transformation types were unused land to woodland and grassland which makes regional vegetation carbon absorption increased significantly,leading to regional carbon uptake increased by 0.897TgC?1.819TgC?0.435TgC?1.839TgC?0.735TgC?1.116TgC?respectively,in the area of Qinghai province,Shaanxi province,Gansu province,Tibet autonomous region,Inner Mongolia Autonomous Region,Ningxia autonomous region.The other six provinces such as Liaoning Province,Jilin Province,Hebei Province,Guangxi Province,Shandong Province,Shanxi province which land use transformation types were farmland to forest and grassland that caused the regional vegetation carbon uptake increased significantly,leading to regional carbon uptake increased by 0.220TgC?0.352TgC?1.064TgC?0.771TgC?1.738 TgC?1.282TgC,respectively.