Geodetector model-based quantitative analysis of vegetation change characteristics and driving forces: A case study in the Yongding River basin in China

Abstract

Vegetation is one of the most crucial components of terrestrial ecosystems, and monitoring vegetation change as well as studying the factors that drive its formation provide significant guidance for restoring ecological biodiversity. The choice of driving indicators for vegetation change in previous studies has not been comprehensive enough, and particularly groundwater depth has not been considered. Therefore, 10 natural factors and 5 human factors were chosen for our study. We adopted the normalized difference vegetation index (NDVI) to measure vegetation growth. In this study, we utilized trend analysis, the Mann-Kendall test, and the Hurst index to investigate the spatiotemporal variance of NDVI in the YDRB. The geographical detector model (Geodetector) was employed to examine vegetation change attributed to human and natural variables. As a result of the study, we found that over the past 22 years, the NDVI in the basin increased from 0.62 to 0.70, with an increase of +0.0040/yr. Land use type is the most significant driver affecting NDVI changes. The interaction of two factors has a greater effect on vegetation change more than a single factor. The relationship between land use type and annual mean precipitation explained 34.5 % of the change in vegetation. Groundwater depth contributed 4.1 % to the explanation of vegetation change. Furthermore, we have determined the optimal range of specific variables conducive to vegetation growth. The results help us further understand the potential driving mechanism of vegetation cover change in the YDRB and provide a theoretical reference for relevant managers to formulate the ecological restoration measures in the basin.