Global trends evaluation in ecosystem isohydricity over decades based on a photosynthesis-stomatal coordination framework

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• Global ecosystem isohydricity dynamics from 1982 to 2016 was estimated. • A photosynthesis-stomatal coordination framework was developed for the estimation. • Global ecosystems have generally shifted towards more isohydric behavior. • Humid woody and arid herbaceous vegetation showed opposite isohydricity trends. • How climatic and structural factors shape isohydricity patterns was demonstrated. The trade-off between carbon assimilation and water use of global ecosystems are undergoing significant shifts under increasing dryness. Isohydric plants tightly regulate stomatal dynamics to stabilize leaf water potential with reduced carbon uptake while anisohydric plants prioritize carbon assimilation at an increasing risk to hydraulic failure. Estimating large-scale shifts in the degree of global ecosystem isohydricity is crucial for understanding how vegetation’s hydrological and carbon cycles adapt to changing climatic conditions. In this study, we estimated monthly global ecosystem isohydricity from 1982 to 2016 by integrating plant hydraulic transport with principles of photosynthesis-stomatal coordination. Results show that global ecosystems have generally exhibited an increasing tendency toward more isohydric behavior, though this shift varies across land cover types and climate zones. Specifically, 32.3 % and 10.2 % of the global vegetated ecosystems had shifted toward more isohydric and anisohydric behavior ( p < 0.05), respectively. Woody, taller vegetation in humid areas exhibited more isohydricity while low herbaceous vegetation in arid areas shifted oppositely. Finally, random-forest analyses revealed hydrothermal factors (light, temperature, water) exhibited stronger explanatory powers for the degree of isohydricity in isohydric ecosystems while CO 2 and ecosystem structural attributes (the fraction of PAR absorbed by vegetation, vegetation height) played the roles in anisohydric ecosystem. This work provides a framework for evaluation of global vegetation isohydric behavior and enhances our understandings of vegetation water-use strategy evolution and highlights the urgency in evaluating ecosystem hydrological resilience under climate changes.