Different effects of Multiple Water Elements on Vegetation: A Case Study of the Yellow River Basin

The effects of water on vegetation have always been a concern. It is an important support as well as a major limiting factor with respect to vegetation growth. By analyzing the spatiotemporal changes and correlations between precipitation (PRE), soil moisture (SM), vapor pressure deficit (VPD), and normalized difference vegetation index (NDVI) in the Yellow River Basin, we explored the different effects of different water elements on vegetation. Our findings reveal the following: (1) NDVI and the three water elements report an increasing trend in the Yellow River Basin, with NDVI increasing most significantly. (2) The changes in vegetation are closely related to arid and humid zoning of the Yellow River Basin. NDVI of arid regions is significantly lower than that of humid regions; additionally, NDVI of natural vegetation in arid regions is lower than that of crops planted in irrigation areas, whereas the opposite is true in humid regions. (3) 92.1% of the Yellow River Basin showed an increase in NDVI, and 76.4% showed a significant increase. The proportions with trends of increasing in PRE, SM, and VPD were 75.40%, 51.88%, and 49.71%, with significant increases of 4.5%, 9.5%, 17.9%, respectively; (4) Vegetation in the Yellow River Basin was most positively affected by PRE, followed by SM and VPD. PRE mainly affected the natural vegetation on both sides of the boundary between the arid and semi-arid regions and the semi-humid regions. SM mainly affected the natural vegetation in the arid and semi-arid regions, whereas VPD mainly affected the crops in the irrigation areas, and the irrigation areas in arid regions were affected the most. These findings contribute to a deeper understanding of the relationship between water elements and vegetation, as well as the formulation of strategies for the healthy development of regional natural vegetation and crops in areas of irrigation.