Temporal and spatial characteristics of grassland degradation in Xinjiang Section of Tianshan Mountains based on remote sensing monitoring and its relationship with climate factors

Grassland plays an important role in environmental protection in Xinjiang. Understanding the temporal and spatial characteristics of grassland degradation and revealing the degradation mechanism would be beneficial for promoting and constructing the ecological civilization of Xinjiang. MODIS NDVI data and remote sensing data of the Xinjiang section of the Tianshan Mountains from 2001 to 2020 were used to analyze the relationship between the temporal and spatial characteristics of grassland degradation and climate factors. Vegetation coverage was used as the remote sensing monitoring index for detecting grassland degradation, and analyses were conducted using methods such as the dimidiate pixel model (DPM), grassland degradation index (GDI), cold/hot spot analysis method, coefficient of variation (COV), and correlation analyses. The results showed the following: 1) The average area of degraded grassland was 34.04% of the total area from 2001 to 2020, and this was categorized as being lightly degraded (with a GDI of 1.67). 2) Slightly-degraded grassland had obvious spatial differentiation characteristics, and they were mainly distributed in the western and central areas of the Tianshan Mountains. Areas of moderately and heavily degraded grasslands were small and not concentrated in a particular region. More than 95% of the regional grassland vegetation coverage had a COV of less than 0.2. The variation in overall coverage was relatively steady, with a small inter-annual fluctuation. 3) From 2001 to 2020, the areas of grassland vegetation coverage affected by climate factors accounted for 44.23% of the total area and were mainly distributed in the west and east of the Tianshan Mountains. Areas of grassland vegetation coverage driven by non-climatic factors accounted for 55.77% of the total area, and these were distributed on relatively flat terrain in the central, northern, and southern sections of the Tianshan Mountains. The results show that non-climate factors play a leading role in grassland changes within the Xinjiang section of the Tianshan Mountains, and they provide a scientific basis for planning the protection and utilization of local grassland resources.