Reversal of Temperature Sensitivity in Vegetation Greenness Rates Along Aridity Gradients Across Global Ecoregions

Abstract

Drought is increasingly reshaping terrestrial ecosystems under climate change, yet how aridity modulates the climatic sensitivities of satellite‐derived green‐up rate (GR) and senescence rate (SR) in natural ecosystems remains poorly understood at the global scale. Here, we combine two decades of satellite observations and climate data sets to identify the primary climatic drivers (temperature, precipitation, solar radiation, soil moisture, and vapor pressure deficit) of maximum GR and SR across 764 global ecoregions and to quantify their sensitivities to interannual variability in climate‐forcing accumulation rates of these drivers. We reveal contrasting temperature‐response patterns along the aridity gradient in arid versus humid ecoregions. In arid ecoregions, decreasing aridity increases the GR sensitivity to temperature accumulation rates during the green‐up phase, whereas in humid ecoregions this sensitivity weakens and can even become negative as conditions become wetter. Similar, though asymmetric, those sensitivity reversal patterns are observed for SR. These findings demonstrate that aridity fundamentally reshapes vegetation‐climate interactions, with important implications for the stability of ecosystem carbon uptake under increasing hydroclimatic variability. By identifying critical transitions in climate sensitivities across aridity gradients, this study provides new insights for improving predictions of ecosystem responses to intensifying drought and for assessing risks to carbon sequestration under future climate change.