Effect of biotic and abiotic factors on inter- and intra-event variability in stemflow rates in oak and pine stands in a Mediterranean mountain area

Abstract

Stemflow, despite being a small proportion of the gross rainfall, is an important and understudied flux of water in forested areas. Recent studies have highlighted its complexity and relative importance for the understanding of soil and groundwater recharge. Stemflow dynamics offer an insight into the rain water that is stored and released from the stems of trees to the soil. Different attempts have been made to understand the variability of stemflow under different types of vegetation, but rather few have focused on the combined influence of both biotic and abiotic factors that affect the inter and intra-storm stemflow variability, and none known in Mediterranean climates. This study presents stemflow data collected at high temporal resolution for two species with contrasting canopy and bark structures: Quercus pubescens Willd.(downy oak) and Pinus sylvestris L. (Scots pine) in the Vallcebre research catchments (NE of Spain, 42º 12'N, 1º 49'E). The main objective was to understand how the interaction of biotic and abiotic factors affected stemflow dynamics. Mean stemflow production was low for both species (~1% of incident rainfall) and increased with rainfall amount. However, the magnitude of the response depended on the combination of multiple biotic and abiotic factors. Both species produced similar stemflow volumes, but funneling ratios of some trees diverged significantly. The combined analysis of biotic and abiotic factors showed that, for events of the same rainfall amount, funneling ratios and stemflow dynamics in each species were highly controlled by the interaction of rainfall intensity and tree diameter (DBH).

Modification of the isotopic composition of rainfall by throughfall and stemflow: The case of Scots pine and downy oak forests under Mediterranean conditions

“…Ikawa et al (2011) ; and d-excess difference between sequential throughfall and sequential rainfall samples higher than for needles. Cayuela et al (2018) found that, above 20 mm of rainfall, funnelling ratios for both species no longer increased.…”

“…For Scots pine, Llorens and Gallart (2000) found that the specific storage capacity of stems was six times higher than for needles. Cayuela et al (2018) found that, above 20 mm of rainfall, funnelling ratios for both species no longer increased.…”

“…Moreover, most recent studies have focused on throughfall (i.e., Allen et al, 2014;Allen, Keim, & McDonnell, 2015;Brodersen et al, 2000;Hsueh, Allen, & Keim, 2016;Kato et al, 2013;Qu et al, 2014;Xu, Guan, & Deng, 2014), whereas shifts in the isotopic composition of stemflow have been much less widely studied (i.e., Ikawa et al, 2011;Kubota & Tsuboyama, 2003) despite recent studies have highlighted its importance as a preferential flow path of water to the soil (Levia & Germer, 2015). In the study area, stemflow accounted for~1% of the incident rainfall; however, stemflow reaching the base of a tree (expressed as L m −2 ) could represent more than 10 times the volume of rainfall; therefore, its influence on the isotopic composition of soil water should not be underestimated (Cayuela, Llorens, Sánchez-Costa, Levia, & Latron, 2018).…”

“…Offsets can be different depending on the canopy characteristics, usually being greater in coniferous forests than in broadleaf forests, possible due to their higher storage capacity (Allen, Keim, Barnard, McDonnell, & Brooks, 2017). In the study area, stemflow accounted for~1% of the incident rainfall; however, stemflow reaching the base of a tree (expressed as L m −2 ) could represent more than 10 times the volume of rainfall; therefore, its influence on the isotopic composition of soil water should not be underestimated (Cayuela, Llorens, Sánchez-Costa, Levia, & Latron, 2018). Moreover, most recent studies have focused on throughfall (i.e., Allen et al, 2014;Allen, Keim, & McDonnell, 2015;Brodersen et al, 2000;Hsueh, Allen, & Keim, 2016;Kato et al, 2013;Qu et al, 2014;Xu, Guan, & Deng, 2014), whereas shifts in the isotopic composition of stemflow have been much less widely studied (i.e., Ikawa et al, 2011;Kubota & Tsuboyama, 2003) despite recent studies have highlighted its importance as a preferential flow path of water to the soil (Levia & Germer, 2015).…”

Water Balance of Mediterranean Quercus ilex L. and Pinus halepensis Mill. Forests in Semiarid Climates: A Review in A Climate Change Context

“…Functional traits, such as life form (tree, shrubs, herbaceous), life habits (evergreen, semi-deciduous, and deciduous), branching architecture, leaf area, specific leaf area, or hydraulic conductivity, establish differences in the structure of a forest and, consequently, in the soil water balance in several vegetation types [21]. Forest canopy characteristics also determine the volume of water flows across a vegetation canopy, such as interception, stemflow, and throughfall [22]. Soil characteristics, such as soil bulk density, soil particle size, porosity, field capacity content, or wilting point moisture content, will also determine water availability for plants and, therefore, the water flows from the surface to the water table [23].…”