Vegetation modulates Earth’s water, energy and carbon cycles. How its functions might change in the future largely depends on how it copes with droughts^1,2,3,4. There is evidence that, in places and times of drought, vegetation shifts water uptake to deeper soil^5,6,7 and rock^8,9 moisture as well as groundwater^10,11,12. Here we differentiate and assess plant use of four types of water sources: precipitation in the current month (source 1), past precipitation stored in deeper unsaturated soils and/or rocks (source 2), past precipitation stored in groundwater (source 3, locally recharged) and groundwater from precipitation fallen on uplands via river–groundwater convergence toward lowlands (source 4, remotely recharged). We examine global and seasonal patterns and drivers in plant uptake of the four sources using inverse modelling and isotope-based estimates. We find that (1), globally and annually, 70% of plant transpiration relies on source 1, 18% relies on source 2, only 1% relies on source 3 and 10% relies on source 4; (2) regionally and seasonally, source 1 is only 19% in semi-arid, 32% in Mediterranean and 17% in winter-dry tropics in the driest months; and (3) at landscape scales, source 2, taken up by deep roots in the deep vadose zone, is critical in uplands in dry months, but source 4 is up to 47% in valleys where riparian forests and desert oases are found. Because the four sources originate from different places and times, move at different spatiotemporal scales and respond with different sensitivity to climate and anthropogenic forces, understanding the space and time origins of plant water sources can inform ecosystem management and Earth system models on the critical hydrological pathways linking precipitation to vegetation.

植被调节地球的水、能量和碳循环。它的功能在未来会如何变化，很大程度上取决于它如何应对干旱^1,2,3,4。有证据表明，在干旱的地方和时期，植被会将水吸收转移到更深的土壤^5,6,7和岩石^8,9水分以及地下水^10,11,12. 在这里，我们区分和评估植物对四种水源的使用：当月降水量（来源 1）、过去储存在较深的非饱和土壤和/或岩石中的降水量（来源 2）、过去储存在地下水中的降水量（来源 3、当地补给）和来自降水的地下水，通过河流-地下水向低地汇聚（源 4，远程补给）落到高地。我们使用逆向建模和基于同位素的估计来检查植物吸收四种来源的全球和季节性模式和驱动因素。我们发现（1）全球和每年，70% 的植物蒸腾依赖源 1，18% 依赖源 2，只有 1% 依赖源 3，10% 依赖源 4；（2）从区域和季节来看，源1在半干旱地区仅占19%，在地中海地区占32%，在冬季干燥的热带地区最干燥月份占17%；(3) 在景观尺度上，源 2 被深渗流区的深根占据，在干旱月份对高地至关重要，但源 4 在发现河岸森林和沙漠绿洲的山谷中高达 47%。由于这四种水源起源于不同的地点和时间，在不同的时空尺度上移动，并对气候和人为力量的敏感性不同，因此了解植物水源的空间和时间起源可以为生态系统管理和地球系统模型提供关键水文路径将降水与植被联系起来。