Ambient bulk deposition, throughfall, and stemflow in a variety of forest stands in Nova Scotia

Abstract

Averaged over one growing season for four conifer and four hardwood stands in central Nova Scotia, incident bulk deposition (IP) was partitioned into 28% canopy interception, 70% throughfall (TF), and 2% stemflow (SF). Hydrogen ion, ammonium, and nitrate fluxes in TF + SF were less than IP; these were presumably consumed by ion-uptake reactions in the canopy or on bark surfaces. All other measured constituents had positive net fluxes, which presumably resulted from some combination of leachage, ion exchange, or washoff of dry-deposited material. The average flux of constituent in TF + SF, expressed as a percent enhancement over IP, was as follows: K, 930; Mg, 274; PO4, 190; Ca, 170; Cl, 116; SO4, 50; Na, 50; H+, −54; NH4, −59; NO3, −69. Tree species differed greatly in concentration and flux of water and nutrient in stemflow. Conifer species generally had lower SF water fluxes, probably because of their greater leaf biomass, which resulted in relatively high rates of canopy interception of IP. Concentrations of K, PO4, and NH4 did not differ between SF of hardwoods and conifers, while NO3 concentration was higher in hardwood SF and concentrations of H+, Ca, Mg, Na, Cl, and SO4 were higher in softwood SF.