Quantifying the contributions of human activities and climate change to vegetation net primary productivity dynamics in China from 2001 to 2016

Vegetation is an important component of the terrestrial ecosystem, driven by climate change and human activities. Quantifying the relative contributions of climate change and anthropogenic activities to vegetation dynamics are essential to cope with global climate change. In this paper, the relative contributions of anthropogenic activities and climate change to net primary productivity (NPP) in China were analyzed by a two-step methodology based on the residual trend analysis (RESTREND). Firstly, the unaltered natural vegetation only affected by climate change (Vclimate) and the vegetation affected by climate change and human activities (Vclimate+human) were separated by the multi-temporal land use land cover (LULC) data. Secondly, RESTREND was applied to NPP of Vclimate and Vclimate+human, respectively, to calculate contributions of climatic factors and human activities to vegetation growth. Results revealed that NPP exhibited a significant increase with 3.13 g C m−2 yr−1 from 2001 to 2016 in China. Climate change and human activities both made favorable impacts on vegetation growth during the study period. Besides, with the separation of Vclimate and Vclimate+human, contributions of climatic factors to vegetation changes increased from 1.57 to 1.88 g C m−2 yr−1, with the proportion of 60.06%. While contributions of human activities to NPP decreased from 1.56 to 1.25 g C m−2 yr−1, with the proportion of 39.94%. Moreover, the average contributions of precipitation, temperature, solar radiation, and other climatic factors to NPP over the entire country were 0.72, 0.24, 0.61, and 0.31 g C m−2 yr−1. Precipitation played a decisive role in vegetation changes in arid and semi-arid regions, temperature was the dominant factor for alpine vegetation dynamics, and solar radiation was beneficial to vegetation growth in most areas of China.