Southern Interior Forest Region


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Changes to Soil Properties and Implications for Soil and Tree Productivity after Harvesting, Site Preparation, or Rehabilitation in ESSF Forests

Author(s) or contact(s): G.D. Hope
Source: Southern Interior Forest Region
Subject: Soil Conservation
Series: Extension Note - RSI
Other details:  Published 2007. Hardcopy is available.
 

Abstract

This note describes results from several studies on the effects of timber harvesting, site preparation, and soil rehabilitation on properties affecting soil productivity and on early tree growth in southern interior Engelmann Spruce-Subalpine Fir (ESSF) forests. Results are presented from research conducted at the Sicamous Creek Silvicultural Systems project and from other relevant research. There were very few, and minor, changes in forest floor and mineral soil chemical and nutrient properties (pH; total C, N, S; available P, and exchangeable cations) over the first five years after forest harvesting at Sicamous Creek. Ten years after site preparation, chemical concentrations in both the remaining forest floor and mineral soil were very similar in four treatments (no treatment, burning, mounding, and scalping). Mineral N (ammonium plus nitrate) production in both the forest floor and mineral soil increased after clearcut harvesting, was elevated in gaps of 0.1 ha or larger, and persisted for at least six years after harvest. The estimated amounts of N lost after harvesting via soil drainage and as stream nitrate were small. Differences in net mineral N production between site preparation treatments at Sicamous Creek, both 5 and 10 years after treatment, were small. The effects of site preparation on production of mineral N were considerably smaller overall than any harvesting-related effects. Short-term changes in ectomycorrhizae and soil fauna have been measured after harvesting and site preparation at Sicamous Creek; however, the relevance of the findings to long-term soil productivity is yet to be determined. After the use of relatively low intensity rehabilitation techniques, the growth of lodgepole pine and Engelmann spruce on rehabilitated access structures, including skid roads, is usually comparable to that in adjacent plantations.

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Updated April 12, 2007