Wood capacitance is related to water content, wood density, and anatomy across 30 temperate tree species

Abstract

Water released from wood tissue during transpiration (capacitance) can meaningfully affect daily water use and drought response. To provide context for better understanding of capacitance mechanisms, we investigated links between capacitance and wood anatomy. On twig wood of 30 temperate angiosperm tree species, we measured capacitance, water content, wood density, and anatomical traits, i.e., vessel dimensions, tissue fractions, and vessel-tissue contact fractions (fraction of vessel circumference in contact with other tissues). Across all species, the strongest predictors of capacitance were wood density (WD) and predawn lumen volumetric water content (VWCL-pd, r2adj=0.44, P<0.0001). Vessel-tissue contact fractions explained an additional [~]10% of the variation in capacitance. Regression models were not improved by including predawn relative water content (RWCpd) or tissue lumen fractions. Among diffuse-porous species, VWCL-pd and vessel-ray contact fraction were the best predictors of capacitance, whereas among ring/semi-ring-porous species, VWCL-pd, WD and vessel-fibre contact fraction were the best predictors. Mean RWCpd was 0.65{+/-}0.13 and uncorrelated with WD. VWCL-pd was weakly negatively correlated with WD. Our findings imply that capacitance depends on the amount of stored water, tissue connectivity and the bulk wood properties arising from WD (e.g., elasticity), rather than the fraction of any particular tissue.