Fan Ying, Miguez-Macho Gonzalo
Department of Earth and Planetary Sciences, Rutgers University, New Brunswick, NJ 08544, USA.
CRETUS, Non-Linear Physics Group, Faculty of Physics, Universidade de Santiago de Compostela, Galicia 15782, Spain.
PNAS Nexus. 2024 Nov 15;3(12):pgae514. doi: 10.1093/pnasnexus/pgae514. eCollection 2024 Dec.
In the vegetation root zone, infiltration () parts in two directions with distinct Earth-system functions. One goes up as evapotranspiration ( + ), returning to the atmosphere (short-circuiting) and affecting short-term weather/climate and the carbon cycle. The other goes down as deep drainage (), flushing the regolith, mobilizing nutrients/contaminates and dissolved minerals into aquifers and rivers, eventually reaching the ocean (long-circuiting) thus regulating global biogeochemical cycles and long-term climate. We ask, what is the modern-day global structure in short- vs. long-circuiting? What forces and feedbacks create such structures? Synthesizing site-studies aided by global modeling, we found that: (i) long-circuiting prevails in evenly wet climates, in well-drained landscapes with a deep vadose zone, in substrates with deep conduits, and with plant biomass below natural equilibrium; (ii) soil B-horizons, via geochemical and vegetation feedbacks, enhance short-circuiting, while deep rock fractures enable long-circuiting even in dry climates; (iii) in dry climate/season and in uplands, plant roots follow into deep vadose zone to tap wet-season ; (iv) plant water-use reinforces shallow , reducing and regolith flushing in dry and season-dry climates; (v) where short-circuiting prevails, a dry soil zone separates modern surface processes from fossil groundwater; and (vi) the + supply depth, regolith flushing rate, and groundwater residence time vary greatly across the land, arising from multiscale drivers/feedbacks among climate, drainage, substrate, and biomass. These findings link site-based process discoveries to Earth-system level structures and functions of water belowground, shedding light on where/when/how the infiltrated rain influences the atmosphere above or the ocean downstream.
在植被根系区，入渗（）分为两个方向，具有不同的地球系统功能。一个方向向上作为蒸散（+），返回大气（短路），影响短期天气/气候和碳循环。另一个方向向下作为深层排水（），冲刷风化层，将养分/污染物和溶解的矿物质输送到含水层和河流中，最终到达海洋（长循环），从而调节全球生物地球化学循环和长期气候。我们要问，当今全球短循环与长循环的结构是怎样的？哪些力量和反馈造就了这样的结构？通过综合全球模型辅助的实地研究，我们发现：（i）长循环在均匀湿润气候、排水良好且包气带较深的地貌、有深层管道的基质以及植物生物量低于自然平衡的情况下占主导；（ii）土壤B层通过地球化学和植被反馈增强短循环，而深层岩石裂缝即使在干旱气候下也能实现长循环；（iii）在干旱气候/季节和高地，植物根系深入包气带以获取雨季的（）；（iv）植物用水强化浅层（），在干旱和季节性干旱气候下减少（）和风化层冲刷；（v）在短循环占主导的地方，干燥的土壤带将现代地表过程与化石地下水分隔开来；（vi）由于气候、排水、基质和生物量之间的多尺度驱动因素/反馈，+供应深度、风化层冲刷速率和地下水停留时间在陆地各处差异很大。这些发现将基于实地的过程发现与地下水资源的地球系统层面结构和功能联系起来，揭示了入渗雨水在何处/何时/如何影响上方大气或下游海洋。
