Under the canopy: disentangling the role of stemflow in shaping spatial patterns of soil microbial community structure underneath trees

Abstract

Summary Stemflow is a spatially concentrated input of rainwater at the base of trees, resulting from precipitation draining down tree branches to the stem. Depending on tree shape, stemflow can represent a significant fraction of the total rainfall that contacts the tree's canopy area, and can become chemically enriched along its drainage path. As a result, stemflow has been hypothesized to influence microbial communities in the receiving soil proximal to the stem. However, previous studies have (i) yielded conflicting results on the significance of stemflow as a driver in bacterial community composition, and (ii) not directly compared communities in soils with and without stemflow receipt. In this study, a stemflow diversion system was employed on Quercus virginiana trees in Skidaway Island (Georgia, USA) to directly compare soil bacterial communities receiving no stemflow to those beneath trees with no diversion system in place. In both treatments, sample distance from the stem significantly influenced bacterial community structure. However, the absence of stemflow resulted in increased bacterial community diversity across all samples. Stemflow diversion also significantly altered longitudinal patterns in the abundance of multiple taxonomic groups. These results support the hypothesis that Q. virginiana stemflow has a significant impact on bacterial soil inhabitants and is a key factor in taxon selection in stem‐proximal communities.

Habitat and tree species identity shape aboveground and belowground fungal communities in central European forests

“…One potential pathway for the connection of the aboveground- and belowground habitats is stemflow ( Magyar et al, 2021 ). Rainwater, which runs down the branches and stems of trees carries a multitude of microorganisms, which are washed into the ground, and may become part of the soil microbiome ( van Stan et al, 2020 ; Magyar et al, 2021 ; Teachey et al, 2022 ). Conversely, fungal particles, such as spores, could be transported by wind in the other direction, from soil to bark, and adhere to bark surfaces and bark biofilms.…”

The Impact of Canopy on Nutrient Fluxes through Rainfall Partitioning in a Mixed Broadleaf and Coniferous Forest

“…Stemflow also acts as a link between the forest canopy and ground soil through the transport of animal remains, plant tissue, and other organic matter to the soil [21,22]. Stemflow has a considerable impact on the moisture conditions, physical and chemical properties, nutritional status, and microbial composition of the soil around the tree stem [23,24]. For example, stemflow leads to higher nutrient and water contents in the areas covered by a vegetation canopy compared to bare land, which is called the fertile island effect [25][26][27][28].…”

Stemflow metazoan transport from common urban tree species (São Paulo, Brazil)

“…Studies have reported changes in the community structure of soil fauna living near tree trunks, with some studies' emphasising stemflow's potential indirect effects on this near‐stem community by altering soil pH (Jóźwiak et al, 2013; Kaneko & Kofuji, 2000; Scheu & Poser, 1996). The only study to directly manipulate stemflow (removing it entirely from the near‐stem soils) found significant changes to soil bacterial community composition and its spatial variability (Teachey et al, 2022). However, the influence of stemflow metazoan transport on forest litter and soil remains an open question.…”