Spatio-temporal changes and factors influencing the grassland fractional vegetation cover in the Bosten Lake Basin, China

The Bosten Lake basin is a primary part of the ecosystem and is critical for water ecological restoration and environmental protection. Research on grassland vegetation change can facilitate environmental protection and sustainable utilization of grassland resources. In this study, the grassland vegetation in the Bosten Lake basin was evaluated using remote sensing image data. A digital elevation model (DEM) and meteorological data of 8 different periods from 1985 to 2020 from the Landsat series satellites, the pixel dichotomy model, linear regression trend analysis, and partial correlation analysis were used to analyze the temporal & spatial pattern changes and factors influencing fractional vegetation coverage (FVC). The results show that: 1) The zonal distribution pattern of "high in mountain area and low in basin" is presented for the FVC of grassland in Bosten Lake basin. The multi-year average value was 0.50, indicating an increasing trend as a whole, and of FVC in the basin. 2) Grassland with a high FVC value in each period was mainly distributed at 2000～3500 m above sea level. As the slope increased, the coverage area of grassland gradually decreased. A grassland area with FVC greater than 0.3 on a semi-sunny slope and a semi-shady slope had an advantageous distribution. 3) From 1985 to 2020, an upward trend was seen for the annual average temperature and precipitation in the Bosten Lake basin, and the two had no significant positive correlation with FVC. However, FVC had a positive correlation with the annual average temperature. The area accounts for 64.72%, mainly distributed in the western high-altitude areas. FVC in the eastern Yanqi Basin and Huangshuigou Valley had a positive correlation with precipitation, and the area was relatively concentrated in space, accounting for 68.70%. This research has provided a reference point for the environmental protection of grassland in the Bosten Lake basin.