Winter chemical leaching from deciduous tree branches as a function of branch inclination angle in central Massachusetts

Leaching is an important process in the biogeochemical cycling of nutrients from above-ground vegetative surfaces to the forest floor. Little is known about winter leaching from deciduous tree species and the influence of branch inclination angle on leachate chemistry. Using a set of field-based isolated branches harvested from mature crowns of Betula lenta, Carya glabra and Quercus rubra, we tested the null hypothesis that during winter neither branch inclination angle nor branch species would have a detectable influence on differences in leachate chemistry and the quantity of intercepted precipitation from the branch surface. Leachate concentrations were significantly greater from branches inclined at 20degrees than 5degrees or 38degrees. Absolute nutrient inputs were also greatest for branches inclined at 20degrees. The significantly enriched branchflow and greater total nutrient input from branches inclined at 20degrees were attributed to increased residence time of intercepted precipitation with the branch surface, the lower probability of branch drip than branches inclined at 5degrees, and only minimal differences in branchflow quantity compared with branches inclined at 38degrees. Branchflow was more enriched from all three branch angles during precipitation events of longer duration and lower intensity than shorter, intense events. The leachate quantities of K+ and Ca2+ differ significantly among species. Carya glabra and Quercus rubra leached more K+ than Betula lenta. All three species leached significantly different amounts of Ca2+, with Quercus rubra leaching the most and Carya glabra the least. The adaptive geometry of deciduous canopy trees should be considered in relation to the interception of precipitation and aqueous leaching during winter when the canopy is leafless. Copyright (C) 2002 John Wiley Sons, Ltd.