Hygroscopic contributions to bark water storage and controls exerted by internal bark structure over water vapor absorption

Abstract Key message Hygroscopicity is a crucial element of bark water storage and can reach >60% holding capacity depending on tree species Bark forms the outer layer woody plants, it directly exposed to wetting during rainfall reacts changes in relative humidity, i.e., may exchange with atmosphere through absorption desorption vapor. A current paradigm hydrology suggests that maximum empties between precipitation events principally controlled by thickness roughness. We hypothesize (1) ability absorb vapor non-rainfall periods (i.e., hygroscopicity) leads partial saturation tissues dry alter rate rainfall, (2) degree hygroscopic function internal structure, including porosity density, varies among species. To address these questions, we conducted laboratory experiments measure interspecific differences physical structure as relates mechanisms common (hickory ( Carya spp.), oak Quercus sweetgum Liquidambar styraciflua ), loblolly pine Pinus taeda )) southeastern United States. Furthermore, considered how properties changed across total bark, inner bark. found distinct difference hickory oak, whereby had 5.6% lower specific 31.1% higher bulk 22.4% resulting hygroscopicity compared oaks. For all species, increased linearly density R 2 = 0.65–0.81) decreased 0.64–0.88). Overall, constitute an average 30% capacity. Therefore, humid climates like those USA, proportion remains saturated non-storm conditions should not be negligible.