Soil water redistribution processes around a tree on a hillslope: the effect of stemflow on the drying process

Abstract

AbstractAlthough many studies have investigated the ecological or hydrological influences of stemflow on soil water dynamics in the wetting process, the process by which stemflow affects soil water redistribution in the drying process has rarely been discussed. To address how soil water depletion occurs around a tree and the effects of stemflow on soil water depletion, we used a 2‐year data set of soil water content to compare soil water depletion in the drying process before (SF period) and after (no‐SF period) the interception of stemflow around a tree on a hillslope. The results revealed a dramatic soil water depletion at locations in the downslope area near to the tree, which was attributed to stemflow and root‐induced pathways. The effect of stemflow on soil water depletion was significant in the short period (0.5 h) after the end of rainfall events, which increased the initial soil water content at the start of drying. The effect of root‐induced pathways enhanced drainage during the drying process and resulted in irregular vertical distributions of changes in soil water content. Although soil water depletion at locations near to a tree would be expected to be greater than in locations farther away, due to root uptake in the drying process, most soil water depletion in the vicinity of a tree occurred in the SF period rather than the no‐SF period. This was mainly attributed to greater instantaneous soil water depletion due to rainwater drainage rather than evapotranspiration, which occurred in the short period between rainfall events. This study furthers our understanding of the separate involvement of stemflow and root channels in the drying process in a warm temperate climate. We also suggest that the double‐funnelling effect of a tree is valid not only for the wetting process but also for the drying process and can result in dramatic variations in soil water dynamics within the stemflow‐influenced and root‐influenced areas of a forested stand. Copyright © 2014 John Wiley & Sons, Ltd.