Abstract: Qilian Mountains is an important ecological security barrier in northwest China. In order to reveal the status and driving mechanism of vegetation cover change in the Qilian Mountains, we obtained 1 km NDVI data from 1982-2022 by integrating GIMMS NDVI and MODIS NDVI, combined with multi-temporal land use, vegetation, geomorphic and meteorological data. Using Theil-Sen trend analysis, Mann-Kendall significance test, and optimal parameter geographic detector model, we analyzed the spatio-temporal variation and spatial heterogeneity of NDVI in the Qilian Mountains. The results showed that vegetation coverage was relatively low in the northern region of Qilian Mountains and relatively high in the southeastern region. From 1982 to 2022, vegetation coverage in Qilian Mountains significantly increased, but appeared a trend of vegetation degradation in the past decade. The average annual precipitation and humidity index were the main driving factors affecting vegetation coverage, with explanatory power of 69.6% and 61.9%, respectively. The interaction between annual precipitation and elevation had a significant impact on the distribution of NDVI. This study revealed the types or ranges of driving factors that promote NDVI growth, providing scientific basis for better understanding the driving factors of NDVI changes in vegetation in the Qilian Mountains.

Key words: vegetation change, driving factor, NDVI, geographic detector with optimal parameters, Qilian Mountains