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Partial cutting in mountainous old-growth forests in coastal British Columbia: harvesting productivity and cost, and residual stand impacts

University of British Columbia

The Forest Engineering Research Institute of Canada (FERIC) worked with International Forest Products Limited (INTERFOR) to plan and implement a partial cutting trial at Chamiss Bay on Vancouver Island's west coast. A study was conducted to investigate the harvesting feasibility of partial cutting in old-growth stands on steep slopes. The study sites were located within the CWHvml biogeoclimatic unit. Harvesting, using manual falling and cable yarding systems, was done in the summers of 1995 and 1996. Two partial cuts (referred to as retention units), two strip cuts, and one clearcut were included in the harvesting study. The retention units had high levels of tree retention, 65 and 70% by basal area, with uniform dispersal of the retained trees. Harvesting productivities and costs were derived from shift-level production reports. Post-harvest surveys were conducted to quantify residual stand damage and soil disturbance levels in the retention units. In the 65% retention unit, falling productivity was 31% lower and unit falling cost was 45% higher than in the clearcut. However, falling productivity was reduced by only 1.6% in the 70% retention unit, compared to the clearcut, mainly because of a marked difference in timber type between this unit and the clearcut. Cable yarding productivity, measured in m 3 (volume of logs) per productive machine hour (m3/PMH), was 34 and 30% lower in the 65 and 70% retention units, respectively, than in the clearcut. Unit yarding costs, based on scheduled machine hours (SMH), were 46 and 32% higher in these same units. These are the relative differences in yarding productivity and cost for the Chamiss Bay trial where a clearcut in similar steep terrain, with no landings, was used for comparison. Post-harvest surveys showed that 33.5 and 37.3% of the residual stems had at least one scar of any size, and 11.7 and 9.7% of the residual stems had at least one scar that was 900 cm2 or greater, in the 65 and 70% retention units, respectively. Exposed mineral soil was observed on only 1.4 and 1.5% of the soil surface area in the 65 and 70% retention units, respectively. The productivity and cost results for the retention units provide important new information to help forest operators plan, budget and implement future partial cutting trials. The trial showed the potential to harvest timber on sensitive sites, with conventional equipment and crews, thus creating an opportunity to augment timber supplies.

Thesis/Dissertation

application/pdf

2009-03-07

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http://hdl.handle.net/2429/5721

Forestry

University of British Columbia

UBCV

DSpace