Turning Points in Vegetation Phenology Trends and Their Relationship to Climate in Arid Central Asia

Grassland phenology is highly sensitive to climate change. Here, we investigate the spatiotemporal patterns of start (start of season (SOS)) and end (end of season (EOS)) dates of the growing season and quantify changes in their climatic controls over the arid Central Asian grassland ecosystems during 1982–2015, which may improve the model performance by considering shifts in primary drivers under ongoing climate change. Our results suggest that temperature played a positive role in advancing the SOS date, with the control of temperature on SOS getting stronger as preseason conditions become warmer but not drier. For autumn phenology, rapid increase in temperature after 1999 in combination with reductions in precipitation jointly contributed to a shift from delayed to advanced EOS. The areas that EOS regulated by either temperature or precipitation have changed between the two subperiods. Our findings suggest that the dynamic controls of temperature and precipitation on grassland phenology and the difference between spring and autumn phenology should be built into phenological models more accurately.