Nutrient Removal and Leaching from a Whole-Tree Harvest of Northern Hardwoods
1982
Hornbeck, James W. | Kropelin, William
Whole-tree harvesting of a northern hardwood stand in New Hampshire removed an average of 111 dry metric tons/ha of biomass, representing 96% of the aboveground total. Nutrient removal in harvested trees averaged 344, 242, 128, and 19 kg/ha for Ca, N, K, and P, respectively. The nutrients removed were between 2 and 3% of estimated total soil capital for Ca and N, and about 1% of total soil capital for K and P. Of estimated available nutrient capital, the removals were 30% for Ca and 85% for K. The harvest was carried out on the lower 40% of a 16-ha watershed. Concentrations of NO₃, Ca, and K in soil solution and streamflow of the harvested watershed increased for 1½ to 2 years. Streamflow concentrations increased by a maximum of 3, 1, and 0.2 mg/liter for NO₃, Ca, and K, respectively. Increased loss of N and Ca by leaching to streams is estimated at < 40 kg/ha. NO₃ in soil solution increased from background levels of 1 mg/liter to a maximum of 95 mg/liter. Ca increased from background levels of 2 mg/liter to a maximum of 19 mg/liter. Concentrations of both ions returned to background levels by the third growing season after harvest. The increases in nutrient ions in streams and soil solution are thought to result from increased mineralization and nitrification immediately after harvest. The harvested area has regenerated rapidly with pioneer and commercial species, perhaps partly because of the enriched soil solution. Nutrient removals and leaching losses by themselves do not seem to deplete total nutrient capital significantly. However, the impacts of whole-tree harvesting upon the processes, mechanisms, and rates by which nutrients are made available for future stands are still of concern.
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