Soil water dynamics around a tree on a hillslope with or without rainwater supplied by stemflow

Abstract

[1] A tree can partition rainfall into throughfall and stemflow (SF), causing water to be funneled around the tree base, and can preferentially divert rainwater in soil layers, causing water to be funneled around tree roots. To determine the effects of each on soil water dynamics, we compared soil water dynamics around a tree on a hillslope on the basis of 2 years of field observations before (SF period) and after (non-SF period) intercepting the stemflow of the tree. Additionally, two sprinkling experiments were conducted using different dye tracers to separately indentify infiltration pathways derived from throughfall and stemflow. The observation results in the SF period showed irregular variations in soil water content, high soil water storage, and significant saturated zone development in the downslope region from the tree, which were attributed to stemflow concentrated on the downslope side of the tree. Although dramatic variations in soil water dynamics disappeared in the non-SF period, asymmetrical soil water response patterns were also observed, which were mainly attributed to root-induced bypass flow. Focusing on the downslope region in the SF and non-SF periods, the frequency of saturated zone generation at the soil-bedrock interface decreased from 58% to 16%, but the frequency of bypass flow occurrence varied little. Saturated zone generation at the soil-bedrock interface underneath the tree in both the SF and non-SF periods suggests that trees are key locations for rainfall infiltration and that tree-induced saturated zone generation should be considered carefully, even in conditions without stemflow supply.Citation: Liang, W.-L., K. Kosugi, and T. Mizuyama (2011), Soil water dynamics around a tree on a hillslope with or without rainwater supplied by stemflow, Water Resour. Res., 47, W02541,

Evidence of double-funneling effect of beech trees by visualization of flow pathways using dye tracer

“…Dye staining experiments have shown that subsurface flow may often take place in living and decayed root channels (e.g. Noguchi et al, 1999;Anderson et al, 2009;Liang et al, 2011). This was confirmed by our study where lateral subsurface flow was promoted by the development of the root network.…”

“…In these studies, dye powder was sprinkled on the soil surface around the base of trunks of desert shrubs (MartinezMeza and Whitford, 1996;Li et al, 2009) or dye solution was sprayed toward the downslope side of tree stems of Stewartia plants (Liang et al, 2011). We designed a novel dye tracer experiment for tracking root channelization of stemflow water.…”

Factors affecting soil moisture spatial variability for a humid forest hillslope

“…The interception and transpiration of water are responsible for the negative correlations of TBA with soil moisture at depths of 10 and 30 cm in area B under dry conditions (Figure e,j). The impacts of throughfall or stem flow near tree trunks can be a possible explanation under very wet conditions (Liang, Kosugi, & Mizuyama, ) as the spatial distribution of TBA is positively correlated for high levels of soil moisture (Figure j,o). The high density of TBA in the transition zone may be associated with the development of preferential flow patterns, which result from changes in the levels of soil moisture as shown in Figure .…”

Impact of interacting bark structure and rainfall conditions on stemflow variability in a temperate beech-oak forest, central Germany

“…Recent research has also linked stemflow producing trees to preferential flow through soils (Liang et al 2007(Liang et al , 2009(Liang et al , 2011, illustrating the potential for transport of dissolved nutrients to biogeochemically active watershed areas (e.g., near-stream saturated zones; Vidon et al 2010). …”