Dependencies of ecological drought on climatic drivers in diverse ecosystems: Implications for water resources...

Ecological drought poses substantial risks to ecosystem functioning through complex climate-vegetation interactions. Focusing on the Yangtze River Basin, a large subtropical region spanning diverse ecosystems from alpine grasslands to evergreen forests, this study integrates Convergent Cross Mapping with an explainable machine learning framework to investigate the causal dependencies and dominant drivers of ecological drought across nine ecosystem types over more than two decades. Results reveal strong nonlinear causal dependencies between water stress and ecological drought across diverse ecosystems, confirming robust hydrometeorological-ecological coupling. Distinct response patterns to climatic drivers are observed between natural and human-dominated ecosystems. Temperature emerges as the primary driver of vegetation responses, explaining 38%-60% of LAI variability across all ecosystem types, and exhibits pronounced nonlinear threshold behavior, with negative effects at low temperatures and increasingly positive influences beyond ecosystem-specific thresholds. These thresholds vary substantially among ecosystems, ranging from approximately 2°C in grasslands to 23°C in drylands and paddy fields, reflecting differentiated thermal sensitivities. Anthropogenic factors act as secondary but critical controls, with irrigation water use exerting a particularly strong influence in cultivated ecosystems. Overall, the identified nonlinear dependencies, ecosystem-specific response patterns, and critical thresholds provide important implications for adaptive water resources management under global change.