The rooting-zone water-storage capacity—the amount of water accessible to plants—controls the sensitivity of land–atmosphere exchange of water and carbon during dry periods. How the rooting-zone water-storage capacity varies spatially is largely unknown and not directly observable. Here we estimate rooting-zone water-storage capacity globally from the relationship between remotely sensed vegetation activity, measured by combining evapotranspiration, sun-induced fluorescence and radiation estimates, and the cumulative water deficit calculated from daily time series of precipitation and evapotranspiration. Our findings indicate plant-available water stores that exceed the storage capacity of 2-m-deep soils across 37% of Earth’s vegetated surface. We find that biome-level variations of rooting-zone water-storage capacities correlate with observed rooting-zone depth distributions and reflect the influence of hydroclimate, as measured by the magnitude of annual cumulative water-deficit extremes. Smaller-scale variations are linked to topography and land use. Our findings document large spatial variations in the effective root-zone water-storage capacity and illustrate a tight link among the climatology of water deficits, rooting depth of vegetation and its sensitivity to water stress.

根区储水能力——植物可吸收的水量——控制干旱时期陆地-大气水和碳交换的敏感性。根区储水能力如何在空间上发生变化在很大程度上是未知的，也无法直接观察到。在这里，我们根据遥感植被活动之间的关系估计全球根区储水能力，通过结合蒸发蒸腾、太阳诱导荧光和辐射估计来测量，以及根据降水和蒸发蒸腾的每日时间序列计算的累积水分亏缺。我们的研究结果表明，在 37% 的地球植被表面，植物可利用的水储量超过了 2 米深土壤的储水能力。我们发现，根区储水能力的生物群落水平变化与观察到的根区深度分布相关，并反映了水文气候的影响，这是通过年度累积缺水极端值的大小来衡量的。较小规模的变化与地形和土地利用有关。我们的研究结果记录了有效根区储水能力的巨大空间变化，并说明了水分亏缺的气候学、植被的根深及其对水分胁迫的敏感性之间的紧密联系。