A meta-analysis of the effects of clearcut and variable-retention harvesting on soil nitrogen fluxes in boreal and temperate forests
Abstract:One of the assumed advantages of variable-retention (VR) harvesting over clearcut harvesting is reduced postharvest leaching losses of nitrogen. We test this assumption by synthesizing results from long-term field trials in a meta-analysis. Overall, clearcutting significantly increased soil NO3-N concentration, NO3-N as a proportion of soluble inorganic nitrogen (SIN), N concentration in leachates, N flux, nitrification rates, and pH, but not total N, NH4-N, SIN concentration, ammonification, or N mineralization rate. The proportion of soil NO3-N in deciduous forests increased immediately and returned to preharvest levels within five years; the effect was delayed in coniferous forests, but levels remained elevated for several years. Deciduous leaf litter decomposed faster and needle litter decomposed more slowly on clearcut sites than in uncut forests. Single-tree selection caused smaller changes in NO3-N than removal of groups of trees (i.e., gap creation) and led to smaller increases in NO3-N as a proportion of SIN than clearcut harvesting. High levels of retention (>70%) were required to maintain uncut stand N-cycling characteristics. Postharvest NO3-N levels could be predicted from NO3-N availability in the uncut forests.
Document Type: Research Article
Affiliations: 1: Department of Forest Science, Faculty of Forestry, University of British Columbia, 2424 Main Mall, Vancouver, BC V6T 1Z4, Canada. 2: Natural Resources Canada, Canadian Forest Service, Pacific Forestry Centre, 506 West Burnside Rd., Victoria, BC V8Z 1M5, Canada. 3: BC Ministry of Forests and Range, Southern Interior Forest Region, 515 Columbia St., Kamloops, BC V2C 2T7, Canada. 4: Department of Forestry, Michigan State University, East Lansing, MI 48824, USA.
Publication date: September 22, 2011
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