Stemflow in a neotropical forest remnant: vegetative determinants, spatial distribution and correlation with soil moisture

Key Message Tree size and exposure is a key driver of stemflow; canopy heterogeneity leads to spatial randomness of stemflow; stemflow impacts soil moisture in superficial layers. Stemflow (SF) plays a relevant role in forest hydrology by delivering rain to the soil around trees. This study sought to explore the effects of tree traits on the amount of SF in an Atlantic Forest remnant in Southeast Brazil using stepwise regressions from April 2016 to March 2017. In addition, we evaluated the spatial association among trees in regard to SF using bivariate Ripley’s K as well as the impact of SF on soil water content (SWC) at five different layers (up to 1 m) using linear regression. We found that the diameter at breast height (DBH), percentage of mosses on the tree trunk, average leaf area, and relative position of the tree within the canopy were selected as explanatory variables in total and monthly average SF models. For the wet season SF models, crown area, percentage of mosses cover on the trunk, average leaf area, and relative position within the canopy were the selected variables, whereas for the dry period SF models, DBH and percentage of mosses were selected. A complete spatial randomness (CSR) between the SF classes was confirmed. We observed that SF impacted the SWC in the superficial layers. Therefore, tree size, exposure, and seasonal differences were the key drivers of SF amount due to the leaf losses during the dry period. Heterogeneity of the canopy is probably responsible for the CSR of SF in the study area. We expect that this study will contribute to the understanding of the hydrological processes in the Atlantic forest hotspot by clarifying the aspects of water capture by trees.