A review of stemflow generation dynamics and stemflow‐environment interactions in forests and shrublands

Abstract

Many geoscientists now recognize stemflow as an important phenomenon which can exert considerable effects on the hydrology, biogeochemistry, and ecology of wooded ecosystems and shrublands. Despite the explosive growth of stemflow research, until this review there has been no comprehensive attempt to summarize and synthesize this literature since 2003. Topical areas of substantive new knowledge in stemflow research include the following: (1) the interrelationships among stemflow and meteorological conditions, especially within individual rain events; (2) the dynamic interplay between stemflow and canopy structure; (3) stemflow and the cycling of solutes and transport of particulate matter; (4) stemflow and its interactions with canopy fungi and corticolous lichens; and (5) stemflow-soil interactions. Each of these five topical areas of substantive new stemflow research is summarized and synthesized, with areas of future research opportunities discussed. In addition, we have reviewed the parameters which can be used to describe stemflow and critically evaluate their utility for different purposes. This review makes a call for scientists studying stemflow to utilize common metrics in an effort to increase the cross-site comparability of stemflow studies. Capitalizing on the insights of prior research, exciting research opportunities await hydrologists, biogeoscientists, and forest ecologists who will conduct studies to deepen our knowledge of stemflow which will enable a better and more accurate framing of stemflow in the larger context of watershed hydrology and biogeochemistry.

The effects of stemflow on redistributing precipitation and infiltration around shrubs

“…The inclination of the main branches was various in all the shrubs, with a relatively wide range of insertion angles (46-64°, C. korshinskii; 48-70°, H. rhamnoides; Table 1). It is known that stemflow is enhanced when the plant structure is cone or funnel shaped, since vertically orientated branches with insertion angles greater than 45° measured above the horizontal promote water flow towards the trunk (Levia and Germer, 2015;Pypker et al, 2005). A funnel shape is indeed a prerequisite for high stemflow production but is not sufficient on its own because the position of the leaves and their orientation and size also affect stemflow (Nanko et al, 2006;Park and Cameron, 2008).…”

“…Throughfall is usually the major understory rainfall flux with growing-season values often representing >70% of the incident rainfall. Levia and Germer (2015) found that stemflow values accounted for 3.5%, 11.3% and 19.0% of rainfall for tropical, temperate and semiarid regions, respectively.…”

“…However, stemflow is almost always considered as a minor component of forest canopy water budgets as compared to interception and throughfall, and therefore it receives minor attention and is under-represented in the literature (Llorens and Domingo, 2007). Most previous studies about stemflow have been conducted in tropical and temperate forests primarily (Levia and Germer, 2015;Tang, 1992;Wang et al, 2013); by contrast, relatively few studies on the characteristics of stemflow were documented for shrub vegetation in semiarid and arid regions (Carlyle-Moses, 2004), and almost no longterm experiments were conducted (more than 5 years).…”

What have we learnt about Mediterranean catchment hydrology? 30 years observing hydrological processes in the Vallcebre Research Catchments

“…In fact, this study emphasizes the need of combining both biotic and abiotic factors to understand stemflow dynamics. Moreover, despite the underestimation of stemflow in most hydrological studies because it represents only a small percentage of incident rainfall (Levia and Frost, 2003;Levia and Germer, 2015), stemflow intensities, much greater for some moments than the intensity of rainfall, highlight the paramount role of stemflow as a hotspot of infiltration and soil water content dynamics.…”

Hygroscopicity of the bark of selected forest tree species

“…According to Voigt & Zwolinski (1964) the amount of water flowing down the tree stem depends more on bark properties than on meteorological conditions. It has been observed that trees with rough bark have a higher water storage capacity and generate a smaller stemflow than trees with smooth bark (Voigt 1960, Levia & Frost 2003, Levia & Germer 2015. Van Stan et al (2015) used a LaserBark to compute bark microrelief, ridge-to-furrow amplitude and slope metrics for Fagus sylvatica L. and Quercus robur L. They observed that a smaller ridge-to-furrow amplitude and slope for Fagus sylvatica significantly lowered the bark water storage capacity, which strongly correlated to maximum funneling ratios and permitted stemflow generation at lower rain magnitudes, while larger ridge-to-furrow amplitude and slope values for Quercus robur reduce funneling, diminishing stemflow drainage for larger storms.…”