Climate controls how ecosystems size the root zone storage capacity at catchment scale

Abstract

The root zone moisture storage capacity (S R) of terrestrial ecosystems is a buffer providing vegetation continuous access to water and a critical factor controlling land‐atmospheric moisture exchange, hydrological response, and biogeochemical processes. However, it is impossible to observe directly at catchment scale. Here, using data from 300 diverse catchments, it was tested that, treating the root zone as a reservoir, the mass curve technique (MCT), an engineering method for reservoir design, can be used to estimate catchment‐scale S R from effective rainfall and plant transpiration. Supporting the initial hypothesis, it was found that MCT‐derived S R coincided with model‐derived estimates. These estimates of parameter S R can be used to constrain hydrological, climate, and land surface models. Further, the study provides evidence that ecosystems dynamically design their root systems to bridge droughts with return periods of 10–40 years, controlled by climate and linked to aridity index, inter‐storm duration, seasonality, and runoff ratio.