Bark Effects on Stemflow Chemistry in a Japanese Temperate Forest I. The Role of Bark Surface Morphology

Abstract

Stemflow can be an important pathway for the drainage of precipitation and related solutes through tree canopies to forest soils. As stemflow must drain along bark surfaces, the effects of bark structure on stemflow chemical composition is merited. This study examines the relationship between stemflow chemistry and bark surface structure for six species of varying bark morphology (four deciduous broadleaf trees and two evergreen coniferous trees) at a montane and an urban site in Japan. Stemflow from smooth-barked species contained greater concentrations of solutes that appear to be rinsed from the stem surface (i.e., sea salt aerosols); while, rougher-barked tree species contained greater or less concentrations of solutes that appear to be leached (e.g., Ca2+) or taken-up (e.g., inorganic N) by the bark, respectively. Site-specific atmospheric environments also influenced thee bark-stemflow chemistry relationships—where the greater elemental deposition in the urban plot generally resulted in greater stemflow chemistry than observed in the lower-deposition montane plot. Our results therefore suggest that the dynamics of dry deposition wash-off by stemflow, and the exchange of dissolved solutes between stemflow and the bark surface, are influenced by the surface structure of the bark and the site’s atmospheric environment. Therefore, the interactions between bark surface structure and its surrounding atmospheric environment are important factors in the stemflow-related elemental cycling between the tree and precipitation.

Bark Effects on Stemflow Chemistry in a Japanese Temperate Forest II. The Role of Bark Anatomical Features

“…The target species were selected according to their bark morphology by moderate, roughness, coarse, and with or without longitudinal tear as following a previous study by Oka et al (2021). The smooth and mottled bark surface types was represented by Clethra barbinervis Sieb.…”

“…The amount of materials captured on the bark varies with the external bark structure-where rough bark on stems, for instance, has been observed to capture nearly 10 times more particles (by mass) than the same area of smoother branch bark surfaces (Xu et al, 2019). There are several studies that have examined the interactions between stemflow chemistry and bark surface structure (Levia and Germer, 2015), and this was the topic for the first part of our research (Oka et al, 2021). Within the bark, however, there are concentrated intracellular solutions that the draining stemflow waters may be able to leach (Klemm et al, 1989).…”

“…The ability for draining stemflow to leach solutes from the bark may depend on bark anatomy, but this has not been investigated to our knowledge. Thus, this manuscript details research that continues from Oka et al (2021), examining relationships between bark external anatomical traits and stemflow chemistry. Oka et al (2019Oka et al ( , 2021 suggested that Cl − and Na + , which are thought to be derived from dry deposition on the tree surface, are easily washed away in the stemflow of smooth bark, while species with coarsely split bark are more likely to leach cations and organic matter, especially Mg 2+ , Ca 2+ , and K + .…”

“…Thus, this manuscript details research that continues from Oka et al (2021), examining relationships between bark external anatomical traits and stemflow chemistry. Oka et al (2019Oka et al ( , 2021 suggested that Cl − and Na + , which are thought to be derived from dry deposition on the tree surface, are easily washed away in the stemflow of smooth bark, while species with coarsely split bark are more likely to leach cations and organic matter, especially Mg 2+ , Ca 2+ , and K + . The external morphology of bark makes a significant contribution to the solute composition and concentration of stemflow, while the thickness and internal morphology of bark are also expected to affect the mechanisms of this bark-water solute exchange.…”

“…The purpose of this study is to examine how solute leaching [focusing on Mg 2+ , Ca 2+ , and K + per the results of Oka et al (2021)] relates to bark anatomical differences among six study tree species in Japan to evaluate bark functions in the exchange of macronutrient cations with stemflow. To accomplish this aim, laboratory experiments were designed to observe the amount, timing, and rates of different solutes leached from the surface of various types of bark.…”