Canopy structure metrics governing stemflow funnelling differ between leafed and leafless states: Insights from a large‐scale rainfall simulator

Abstract

An increasing number of studies have examined the effects of various biotic and abiotic factors on stemflow production. Of those that have ascribed the importance of canopy structure to stemflow production, there has been a bias towards field studies.Coupling Bayesian inference with the NIED (National Research Institute for Earth Science and Disaster Resilience, Tsukuba, Japan) large-scale rainfall simulator, this study leveraged a unique opportunity to control rainfall amounts and intensities to pinpoint the canopy structural metrics that differentially influence stemflow funnelling ratios for three common tree species between leafed and leafless canopy states. For the first time, we examined whether canopy structure metrics exert a static control on stemflow funnelling ratios or whether different elements of canopy structure are more or less important under leafed or leafless states, thereby allowing us to determine if tacit assumptions about the static influence of canopy structure on stemflow production (and funnelling) are valid (or not). Rainfall simulations were conducted at 15, 20, 30, 40, 50, and 100 mm h À1 under both leafed and leafless tree conditions (12 simulations in total) to detect any differential effects on the presence or absence of foliage on stemflow funnelling ratios. For leafed conditions, the highest percentages of best-fitting models (ΔDIC ≤2) indicated that stemflow funnelling ratios were mainly controlled by total dry aboveground biomass (B all ), diameter at breast height (D BH ), total dry foliar biomass (B f ), tree height (H), and woody to foliar dry biomass ratio (BR). Whilst for the leafless state, the highest percentages of best-fitting models Shin'ichi Iida and Kathryn I. Wheeler contributed equally to this study.

Introducing Pour Points: Characteristics and Hydrological Significance of a Rainfall‐Concentrating Mechanism in a Water‐Limited Woodland Ecosystem

“…Iida et al. (2021) found inconsistent relationships between stemflow production and foliation as well. At present, variation in pour point fluxes for a constant rainfall intensity cannot be simply predicted as a linear function of foliation and branch angle.…”

“…Finally, the rainfall simulation experiments indicated that pour point fluxes could vary with the degree of foliation and the branch angle, but did not uncover consistent simple relationships between canopy architecture and the pour point flux. Iida et al (2021) found inconsistent relationships between stemflow production and foliation as well. At present, variation in pour point fluxes for a constant rainfall intensity cannot be simply predicted as a linear function of foliation and branch angle.…”

“…F. Levia & Germer, 2015;Martinez-Meza & Whitford, 1996;Van Elewijck, 1989), and higher leaf area (Staelens et al, 2011). However, neither of these observations is universal (Garcia-Estringana et al, 2010;Iida et al, 2021;D. F. Levia & Germer, 2015).…”

“…Laboratory and field studies have linked increased stemflow volumes to greater branch inclination above horizontal (Bialkowski & Buttle, 2015; Crockford & Richardson, 1990; D. Levia et al., 2015; D. F. Levia & Germer, 2015; Martinez‐Meza & Whitford, 1996; Van Elewijck, 1989), and higher leaf area (Staelens et al., 2011). However, neither of these observations is universal (Garcia‐Estringana et al., 2010; Iida et al., 2021; D. F. Levia & Germer, 2015). There is also experimental evidence for an increase in drop size recorded underneath the canopy in the absence of leaves (Nanko et al., 2016, 2022), which may indicate higher rates of pour point formation.…”

Quantity or Efficiency: Strategies of Self‐Organized Xerophytic Shrubs to Harvest Rain

“…The positive relation of biomass with stemflow yield and funneling ratio agreed with the reports on Myricaria squamosa (Zhang et al., 2015), Cryptomeria japonica D. Don, and Chamaecyparis obtuse (Siebold & Zucc.) Endl (Iida et al., 2021). Besides, relative to scattered shrubs, the stronger supporting structure of clumped shrubs (i.e., smaller LLW (2.509 vs. 2.640, unitless)) contributed to their stemflow advantages.…”