Detection and attribution analysis of hotspots of ecosystem gross primary production change in China

Terrestrial gross primary production (GPP) is a key process for understanding land ecosystem dynamics．Detecting hotspots of GPP change and analyzing impact factors are helpful to understand ecosystem carbon cycle and provide reference for ecological environment protection and management．In the present study, trend analysis and hotspot analysis were combined to detect hotspots of GPP changes in China and to analyze the impact of natural factors and human activities on GPP changes．GPP was found to have an increasing trend from 1982-2017 in China, with an average change of 1.92 g·m⁻²·a⁻¹．The hotspots with significant positive GPP change were found located in eastern Qinghai-Tibet Plateau, The Loess Plateau, North China Plain and The Yunnan-Guizhou Plateau．Hotspots with significant negative GPP change were found located in the southern part of Tibet, The Yangtze River delta and the southeast coastal areas．The combined influence of temperature, precipitation and radiation on GPP was greater than any single natural factor, correlation between temperature and GPP was the highest．The proportion of pixels with temperature and human activities as the dominant factors of GPP change was the highest, accounting for 43.86%, followed by temperature (26.86%)．The influence of temperature and human activities varied in different hotspots．On the whole, they played a positive role in 4 GPP increasing hotspots and a negative role in 3 GPP decreasing hotspots．