Key Driving Factors of Ecosystem Resilience Under Drought Stress in the Dongjiang River Basin, China

Abstract

Under global climate change, frequent droughts threaten ecosystem functions, but how drought characteristics affect ecosystem resilience remains unclear. Focusing on the Dongjiang River Basin, China, we identified drought events at an 8-day scale from 2000–2024 using multi-source remote sensing and reanalysis data. The water use efficiency-based resilience index (Rde) was calculated, and a random forest model quantified the contributions of 21 potential driving factors. The model explained 68% of Rde variance (R2 = 0.68, RMSE = 0.12). Downward shortwave radiation was the primary factor, followed by antecedent water use efficiency and soil moisture anomaly, with drought intensity and air temperature ranking fourth and fifth. All dominant factors exhibited nonlinear threshold effects: Rde decreased significantly after radiation exceeded ~110 W·m−2·(8d)−1; Rde declined when standardized soil moisture anomaly fell below −2.0; and Rde increased sharply when drought intensity exceeded 12%. Drought intensity far outweighed duration and severity, establishing it as the key drought attribute. This study reveals the dominant drivers and their thresholds governing ecosystem resilience in the Dongjiang River Basin, providing quantifiable indicators for ecological drought early warning.