Spatiotemporal variation in vegetation coverage and its response to climatic factors in the Red River Basin, China

Vegetation coverage is a critical factor in soil conservation and improving the ecological environment. As an important ecological corridor connecting China's southwest and Southeast Asia, the Red River Basin is characterized by vulnerable ecosystems and serious soil erosion. Identifying the heterogeneity in vegetation coverage and its response to climatic factors are critical for ecological protection and soil and water conservation. MOD13Q1 NDVI data with a spatial resolution of 250 m and 16 d temporal resolution were collected from 2000 to 2014. The maximum synthesis method, univariate linear regression, Hurst exponent, and partial correlation analysis were used to detect the spatiotemporal variation and sustainability of vegetation coverage and characterize the relationship between vegetation NDVI and climatic factors in the wet season in the Red River Basin. NDVI showed a rather significant increasing trend in the wet season. The "corridor-barrier" function of valleys and mountains affected the spatiotemporal patterns in the Longitudinal Range-Gorge Region. Areas of improved, degraded, and stable vegetation coverage accounted for 50.1%, 27.1%, and 22.8% of the total, respectively. The role of precipitation was higher than temperature in the interaction between NDVI and climatic factors. A time lag effect was found in the NDVI response to rainfall and temperature variation. Different vegetation types showed various spatiotemporal responses to climatic factors. Human activities, especially the implementation of the Grain for Green Project (GFGP), affected the spatial and temporal patterns of vegetation coverage.