Stocker Benjamin D, Tumber-Dávila Shersingh Joseph, Konings Alexandra G, Anderson Martha C, Hain Christopher, Jackson Robert B
Department of Earth System Science, Stanford University, Stanford, CA USA.
Department of Environmental Systems Science, ETH, Zürich, Switzerland.
Nat Geosci. 2023;16(3):250-256. doi: 10.1038/s41561-023-01125-2. Epub 2023 Feb 9.
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（即植物可利用的水量）控制着干旱时期陆地与大气之间水和碳交换的敏感性。根区储水能力在空间上如何变化很大程度上未知且无法直接观测。在此，我们根据结合蒸散、太阳诱导荧光和辐射估算得到的遥感植被活动与根据降水和蒸散的日时间序列计算出的累积水分亏缺之间的关系，全球范围内估算根区储水能力。我们的研究结果表明，在地球37%的植被表面，植物可利用的水分储量超过了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测到的根区深度分布相关，并反映了水文气候的影响，水文气候以年度累积极端水分亏缺的幅度来衡量。较小尺度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，并说明了水分亏缺气候学、植被生根深度及其对水分胁迫的敏感性之间的紧密联系。
