This extension note describes some of the effects of timber harvesting on the soils at the Sicamous Creek Silvicultural Systems Project study site for the 5-year period since harvesting. The study site is located in the ESSF zone near Sicamous, B.C. Five harvesting treatments were applied: no harvesting, single-tree selection, 0.1-, 1-, and 10-ha clearcuts. A variety of studies investigated the effects of opening size and distance from the edge of the cut area on soil nitrogen dynamics, nutrient cycling, soil food webs, ectomycorrhizae, and fine roots. Generalizations regarding short-term effects on the below ground organisms and processes are difficult. A complete absence of sporocarp fruiting, increased rates of nitrogen mineralization and increased nutrient leaching losses were noted in the first growing season after harvest. Decreased ectomycorrhizal diversity and fine-root biomass were measured after one growing season. Shifts in community structure occurred for micro-arthropods and bacteria while no discernible impact was detected for decomposition rates and total collembola numbers. All these changes persisted for up to 5 years after treatment, although nutrient leaching peaked after 3 years. The major influence of the forest edge into the opening occurred within approximately one-half of the tree canopy height of the uncut forest. Cutting practices that create a range of opening sizes would best maintain the widest variety of soil biological diversity and functions.
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Updated April 19, 2007