Enhanced Dependence of China's Vegetation Activity on Soil Moisture Under Drier Climate Conditions

Vegetation growth is known to be largely dependent on the availability of soil moisture (SM), yet the changes in response to climate change are still not clear. Here, we use the long-term satellite-observed normalized difference vegetation index (NDVI) and reanalysis SM to examine changes in the dependence of vegetation on SM across the vegetated lands of China during 1982–2015. The results show that the strength of the relationship between the interannual variability of the growing season NDVI and SM (partial correlation coefficient R_SM-NDVI) significantly increased in over 45% land fractions from 1982 to 2015. The strongest increasing trend occurred in the originally SM-dependent areas, indicating an enhancing regime. The increase in R_SM-NDVI coincided with a decrease in precipitation and SM, highlighting the key role of drying in driving the increase in R_SM-NDVI. We also demonstrate that North China is a hotspot region which is more vulnerable to soil dryness. Our findings would be valuable for vegetation planning and management in China under future drying and intensified drought conditions.