Spatial and temporal variations in surface soil moisture and vegetation cover in the Loess Plateau from 2000 to 2015

The "Grain for Green" project utilizes large-scale revegetation to improve the local environment in the Loess Plateau. Understanding the trends in the variations in soil moisture content (SMC) and vegetation after the implementation of this project is necessary. This study examined the spatial and temporal variations in SMC and vegetation cover in the Loess Plateau after 1999. Furthermore, interactions between SMC and vegetation cover (e.g., spatial distribution and temporal variation) were assessed. The results of this study showed that (1) the SMC and vegetation cover increased in most of the Loess Plateau from 2000 to 2015; (2) both SMC and vegetation cover are predicted to decrease after 2015; (3) the increase in precipitation promoted SMC in the northwestern region, but the impact on vegetation cover was not significant; (4) the spatial variation in SMC exhibited a positive correlation with the spatial variation in vegetation cover, however, the difference in their cycle of change indicated that the interaction between SMC and vegetation cover varied over time. The most important results indicated that SMC and vegetation cover have begun to decrease since 2015.