Interannual variability in summer climate change controls GPP long-term changes.

Global environmental change is rapidly altering the dynamics of terrestrial vegetation, with implications for the functioning of the Earth system and the provision of ecosystem services. How vegetation responds to a changing environment is an important scientific issue, but there is a lack of coverage of the relative contributions that long-term variation and interannual variability in vegetation across seasons play in ecosystem response to global change. Here, we used four terrestrial ecosystem models provided by MsTMIP to examine four key environmental drivers of gross primary productivity (GPP) change over the period 1901-2010. Our findings showed that (1) for all seasons, interannual variability in climate change are the main environmental factor controlling seasonal GPP variability. (2) Summer is the key season controlling the variation of annual GPP, and its long-term trend and interannual variability can explain 61.50% of the variation of grassland GPP in China. (3) Interannual variability in summer climate change exceeded the CO fertilization effect and nitrogen deposition as the controlling component (more than 40%) of long-term variation in Chinese grassland GPP. These studies highlight the important role of interannual variability in climate in reshaping the seasonality of vegetation growth, and will provide a precursor to future environmental drivers that can be precisely attributed to global vegetation change.