Abstract
Timber Supply Reviews (TSR 1) and the implementation of the Forest Practices Code and Kootenay Boundary Land Use Plan, indicate that the allowable annual cut in the Nelson Forest Region may be reduced by 13.3%-21.7 %. Commercial thinning may offset some projected wood supply fall downs through improved harvesting flexibility.
The main objectives were: 1) Complete an overview analysis of suitable forest types and candidate stands for commercial thinning, 2) Complete a field inventory of a portion of the themed stands to determine their suitability for thinning, and 3) Test the impact of different levels of thinning on wood flow in Arrow Timber Supply Area (TSA) using a modified FSSIM harvest forecast model.
Locally-developed inventory, utilization and economic suitability criteria were used to identify and theme map potential areas in the Arrow and Cranbrook TSAs. Reconnaissance surveys were conducted in a portion of the themed stands. Stands that met minimum suitability criteria were cruised to determine potential harvest volumes and residual stands conditions. District staff reviewed the cruising results, and after follow-up field inspections, selected the actual stands that would later be thinned.
Theming initially identified approximately 44,557 hectares in the Arrow and 24,843 hectares in Cranbrook. Lack of road access subsequently eliminated approximately 85-90% of the themed stands as potential candidates for thinning. Reconnaissance surveys in the accessible stands indicated that approximately 80-90% of the stands surveyed were unsuitable for thinning, mainly due to inappropriate stand structure or low potential thinning volumes. Only a subset of surveyed stands was cruised in each TSA. The cruising identified between 10,298 and 14,195 m3 of potential thinning volume in Arrow and 32,650 to 41,704 m3 in Cranbrook, depending on the minimum utilization level. However, District staff anticipate that only 40-60% of the cruised stands may actually be thinned due to stand structure and overriding management objectives.
Resource Emphasis Area management objectives, current stand structure, biological potential of the stand to maintain adequate growth after thinning and utilization level by species must all be considered when developing thinning prescriptions. There are trade-offs between potential thinning volume, stand growth and forest health depending on the emphasis of any of these factors.
In the Arrow TSA, a 2-5% increase in short term wood supply was indicated by the modelling when the thinning was concentrated in visually constrained Resource Emphasis Areas. The positive effects on wood flow were maximized at 400 hectares per year but were only sustainable for the first six decades. The increase in wood flow attributed to commercial thinning is not additive to the increase from other partial cutting practices in constrained areas. Some of the benefits may already be realized due to the amount of partial cutting currently being practised.
Recommendations are made for future projects of this nature.
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Updated April 12, 2007
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