Widespread root-zone water bypass for various climates and species: Implications for the ecohydrological separation understanding

Root-zone water storage is a core component of many hydrological systems, and a critical variable influencing water transport in the soil-vegetation-atmosphere continuum and biogeochemical processes. However, the dynamics of water bypass and replenishment in root-zone during precipitation infiltration processes have been rarely investigated. Here we employed a piecewise isotope balance method to estimate the proportion of root-zone water replenished by precipitation, and conducted a meta-analysis to check the patterns of water bypass and replenishment in root-zone for various species across five climate zones and examined the potential influencing factors. The results show that high proportion of root-zone water replenishment is likely to appear during the transition period from dry season/soil to wet season/soil. Root-zone water bypass is widespread under various climates, which is likely to occur by downward drainage under wet soil condition or via evaporation loss under high atmospheric demand. Antecedent soil water condition and rooting depth are found to be the two key factors regulating dynamics of root-zone water bypass and replenishment. These findings provide useful insight into our understanding of ecohydrological modeling (e.g., non-well-mixed water pool in soils) and plant responses to precipitation pulses.