Effects of canopy components on throughfall chemistry: An experimental analysis.

Five canopy components of subalpine balsam fir forests (branches with young needles, branches with old needles, non-foliated twigs, lichen-covered twigs, and boles) were treated with simulated rain to test the influence of these components on throughfall and stemflow chemistry. Effects on the fluxes of potassium, sodium, hydrogen, sulfate, nitrate and ammonium ions by the canopy components were tested in relation to rain application rate, duration of rain, and time since the last rain. Interactions between ionic behavior and components were complex. In general, the ionic behavior ranged from high levels of net efflux to mixed influx-efflux to high levels of influx in the order: sulfate, potassium, sodium, nitrate, hydrogen, ammonium. In cases in which application rates produced significantly different results, net flux rates increased with application rate. Branch components mostly ranged from low flux rates (either influx or efflux) to high rates according to the order: young needles<old needles<twigs<lichencovered twigs.