Abstract:

To investigate the spatiotemporal variation trend of fractional vegetation cover(FVC)in the agro-pastoral ecotone of Gansu Province from 2000 to 2024 and to elucidate the influence of natural and human factors on its change. This study utilized the monthly Normalized Difference Vegetation Index (NDVI) data,which were obtained by the maximum synthesis method,and FVC was subsequently inverted using the Pixel Dichotomy Model.Spatial auto-correlation analysis and GeoDetector model were employed to examine the spatiotemporal characteristics and spatial agglomeration effect of FVC,as well as to quantify its response to natural and human factors. This study indicated:1)From 2000 to 2024,the fractional vegetation cover in the agro-pastoral ecotone of Gansu Province exhibited a temporal trend of "gradual increase followed by a sharp decline" with significant differences between regional variation,and the proportion of areas with low and lower medium vegetation coverage exceed 50%,indicating significant ecological degradation.2)FVC showed significant spatial heterogeneity and clustering.Its spatial distribution followed the a pattern of "higher in the south and lower in the north,higher at the periphery and lower in the interior". The degradation degree of the southern region was worsethan that of the northern.High FVC value was concentrated in the southern ecological barrier region,where as the low values were clustered in the northern transition zone. 3)The Geo Detector results showed that all factors had significant effects on FVC change (P<0.05),with precipitation,temperature and elevation being the core driving factors. The explanatory power of the factors interactions was consistentlygreater than that of any single factor,with the interaction between precipitation and other factor sbeing the most powerful. However,the increasing explanatory power of human factors suggests the deepening coupling of human-environment system. In the face of the dual pressure of global climate change and human activities,it is urgent to pay attention to the coordinated development of nature and society in ecologically fragile areas and actively explore the human-environmentcoupling pathway to achieve regional sustainable development.

Key words: fractional vegetation cover, temporal and spatial variation, spatial auto-correlation analysis, GeoDetector, the agro-pastoral ecotone of Gansu Province