Effects of whole-tree harvest on soil-water chemistry at five conifer sites in Sweden

Abstract

Logging residues, such as tops and branches, can provide a useful biofuel for large-scale energy production. However, increasing the harvest intensity may affect the soil nutrient stores and water quality. Here, effects on soil-water chemistry after stem-only and whole-tree harvesting were investigated using data from five experimental sites in Sweden, representing medium- to high-fertility sites. They were located in recharge areas on mineral soil and harvested between the years 1995 and 2001. Soil-water samples had previously been collected from below the main part of the root zone in study plots subjected to stem-only or whole-tree harvest. Soil-water chemistry data from the five sites were jointly analyzed by ANOVA using seasonal mean concentrations from the first six seasons after clear-cutting. The concentrations of NO3–-N, K+, and Mg2+were significantly different (p < 0.05) between the two harvest regimes, indicating lower levels after whole-tree harvest than after stem-only harvest. No significant differences were detected for electrical conductivity, pH, or the concentrations of NH4+-N, Al, Ca2+, SO42–-S, and Cl–. Measurements at one site suggested that the logging residues left on the ground increased the influx of Cl–to the soil. Simple budget calculations indicated that the nutrient export by logging-residue harvest was greater than the export by leaching during the regeneration phase.