This report summarizes a pilot study that investigated how loads that are applied to skyline systems in second-growth thinning operations affect the line tensions and stress distribution in the backspar. The maximum tension in the skyline occurred when the turn was fully suspended under the carriage. In the backspar that was examined, compression was the critical stress. By recognizing how the critical loads produce stresses on backspars, procedures can be developed that will limit these stresses.
Les chercheurs suggèrent une récolte partielle; dans ce cas, l`éclaircissage des forêts par tranche de 20 ans pendant les périodes de perturbation naturelle des ravageurs. Le résultat est un moyen durable et économique de récolter des arbres et de maintenir des forêts résilientes.
Pacific Forest Products Limited began commercially thinning Douglas-fir dominated second-growth forest on southeastern Vancouver Island with mechanized shortwood systems in 1992. In the summer of 1994, FERIC monitored a thinning operation near Cowichan Lake to determine productivities, costs and impacts to sites and residual stands. The thinning treatment was carried out with a Timberjack 1270 harvester and a Timberjack 910 forwarder.
FERIC studied two commercial thinning systems under comparable conditions. The first involved manual felling, processing, and piling, whereas the second was completely mechanized and used a small single-grip harvester. Two shortwood forwarders with different payload capacities were also studied in this operation. The costs at roadside depended strongly on the hourly wages for the workers. A sensitivity analysis demonstrated that the estimated production costs for the two systems were comparable (at $22.83/m3) when the wages reached $19.22 per scheduled hour.
The researchers suggest partial harvesting - in this case, thinning forests in 20-year increments during the natural pest disturbance periods. The result is a cost-effective and sustainable way to harvest trees and maintain resilient forests.
A commercial thinning study in mule deer winter range was performed in the interior of British Columbia. The commercial thinning was followed by a pre-commercial thinning operation to create a clumpy, multi-storied stand with gaps for regeneration. The Forest Engineering Research Institute of Canada (FERIC) monitored the commercial thinning and pre-commercial thinning operations and determined the costs and productivities of these phases.
A multi-agency trial was established to determine the impacts of commercial thinning on the growth, yield, and development of white spruce stands. The commercial thinning operation was completed using a Timberjack 1270 harvester and a Timberjack 1210B forwarder. The Forest Engineering Research Institute of Canada (FERIC) monitored the harvesting phase, determined the operational cost and productivity of the harvester and forwarder, determined the residual tree damage, and evaluated the effectiveness of a brushing crew in increasing the productivity of the harvester in areas with high densities of non-merchantable trees.