Management Impacts on Nutrient Fluxes in Beech-podocarp-hardwood Forests

Clearfelling and downhill, skyline-hauler extraction of pulpwood and sawlogs in beech-podocarp-hardwood (PB5) forest, followed by slash-burning, produced increased streamflow yields of N, P arid dissolved cations. Nutrient outputs in the first four months after treatment were from 1 to' 1.5 times the normal annual output. Yields of Na, Mg, Ca, and K were from 1 to 6 times the normal output; K output showed the largest increase. Nutrient! and cation concentrations in streamflow remained within drinking water quality limits except for 12 hours following burning, when ammonium-N was greater than 0.5 mg/1. Losses of K from this treatment appear greater than any reported in the literature and constitute 5% of the readily-available K, but less than 0.1% of the total K capital in thei forest and soil. N and P losses are in the low to middle range of results reported from elsewhere. The high K losses are related to: (1) the combination of steep terrain, complete preextraction felling, and the logging method, which concentrated crown material near the stream; (2) the greater fire intensity near the stream which, because of the fuel concentrations and an up-valley wind, converted; much of the slash to K-rich ash; and (3) two small storms which occurred shortly after burning and removed most of the ash from the catchment.