Vegetation evolution and water sensitivity analysis in the source region of the Yangtze River and the Yellow River under the combined drive of energy-temperature-water

• The multiple factors (Energy, water and temperature) can better explain NDVI. • Energy and temperature indirectly affected vegetation by affecting water source. • Precipitation and shallow soil water have the greatest influence on vegetation. • The sensitivity of different landforms and vegetation to water source is different. Due to the combined effects of energy distribution, temperature change and water phase transition, the vegetation eco-hydrological process in the source region of the Yangtze River and Yellow River is highly sensitive to climate change, and its multiple driving mechanisms need to be systematically analyzed. This study analyzed the temporal and spatial evolution of vegetation in the source region of the Yangtze River and the Yellow River. Based on multi-source remote sensing data sets, combined with multi-cross wavelet analysis and structural equation model, a causal chain analysis technique of regional energy distribution-temperature change-water sources composition-vegetation growth was constructed to reveal the driving mechanism of vegetation change in the source region of the Yangtze River and the Yellow River, and further identify its sensitive water sources. The results showed that 82.26% of the regional vegetation in the source area improved significantly from 1982 to 2020. The total effects of temperature, energy and water source factors on vegetation were 0.96,0.78 and 0.34, respectively. However, energy and temperature mainly affected vegetation indirectly through water sources, and the indirect influence coefficients were 0.96 and 0.29, respectively. Water source factors directly affected vegetation, among which precipitation and shallow soil water had the most significant effects. In terms of spatial distribution, precipitation and soil water are crucial to the water supply of cultivated land, forest land, grassland and wetland vegetation. Surface runoff and snowmelt water have a significant impact on grassland, reaching 0.23 and 0.13, respectively. The research results can provide some guiding significance for vegetation restoration and ecological management in alpine plateau area.