NUTRIENT REMOVALS WITH HARVESTING AND BY DEEP-PERCOLATION FROM WHITE BIRCH (BETULA-PAPYRIFERA [MARSH.]) SITES IN CENTRAL NEWFOUNDLAND

The effects of conventional stem-only and whole-tree harvesting on nut rient losses in biomass removal and in leachate fluxes over a 3-yr per iod after cutting three white birch stands in central Newfoundland wer e determined. Losses of nutrients in biomass were proportionately grea ter with more intensive harvesting as tree components with higher nutr ient concentrations (branches, foliage) were removed. Stem-only harves ting removed 126, 9, 51, 126 and 23 kg ha(-1) of N, P, K, Ca and Mg in biomass, respectively. Whole-tree harvesting led to a 19% increase in biomass removal as compared to stem-only harvesting, but nutrient rem ovals with whole-tree harvesting increased by 127% for N, 138% for P, 151% for K, 72% for Ca and 90% for Mg. Nutrient losses in deep percola tion of soil solution during the first 3 yr after harvesting were gene rally greater following stem-only than whole-tree harvesting. This may be the result of increased leaching from slash, increased mineralizat ion beneath slash, and retardation by slash of the successional vegeta tion that could act as a nutrient sink. In the first 3 yr following ha rvesting, leaching losses after whole-tree harvesting were 4, 0.2, 8, 23 and 7 kg ha(-1) of N, P, K, Ca and Mg, respectively, as compared wi th 9, 0.1, 7, 28 and 9 kg ha(-1) of N, P, K, Ca and Mg after stem-only harvesting. Nutrient losses in leachate were generally small compared to losses in biomass removal.