How topographic and pedological factors affect vegetation responses to drought: a study from the Qinling Mountains, China

Under global warming, the Qinling Mountains, a region highly sensitive to climate change, face increasing challenges in understanding vegetation responses to drought, particularly due to differences in topographic and pedological factors. This study employed three vegetation indices—EVI, GPP, and LAI—together with the Standardized Precipitation Evapotranspiration Index (SPEI) to evaluate vegetation responses to drought. Additionally, random forest and structural equation models were used to quantify the direct and indirect effects of topographic and pedological factors on vegetation response to drought. Our results suggested that from 2001 to 2020, the growth rate of EVI in Qinling exceeded that of GPP and LAI, indicating stronger drought-induced inhibition of GPP and LAI. The time lag effect of drought promoted vegetation growth in 47–62 % of the study area, while cumulative drought effects inhibited growth in 79–91 % of vegetation. Anthropogenic changes in vegetation types intensifying sensitivity to drought, anthropic vegetation showed a higher time lag response coefficient (0.05) than natural vegetation. Nutrients such as nitrogen, phosphorus, and potassium improved vegetation drought resistance by regulating physiological processes. Elevation influenced drought vulnerability by shaping regional climate and vegetation distribution, while bedrock depth and slope regulated access to water storage during drought. Drought vulnerability, water availability, and vegetation resistance had influence coefficients of 0.10, 0.20, and −0.29, respectively, in cumulative drought responses, while water availability during time lagged drought effects had a dominant coefficient of 0.42. These findings provide essential insights into vegetation responses to drought and offer a theoretical basis for addressing global climate change and drought impacts.