Graduate Project
 

The DEERHORN case study: a production and cost analysis of a single-grip harvester and small cable yarder performing a thinning/salvage operation in eastern Oregon.

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  • Land managers in the Blue Mountains of eastern Oregon are currently faced with large areas of forest with health problems and extreme levels of fuel loading in the stand and on the forest floor. These conditions resulted from a combination of insect infestations, past management practices and the elimination of fire from the local ecosystems. These forests are now overstocked, diseased and contain vast amounts of dead woody debris on the forest floor posing a serious threat of large destructive fires. This paper presents an economic analysis of a harvesting system aimed at treating these stands while minimizing soil impacts. A combined thinning of the dense stands and salvage logging of the larger fuels from the forest floor was completed using a single-grip harvester to process the stems into logs and a small cable yarder to transport the logs to landings. The terrain on the site was flat and therefore presented logistical challenges for yarding. This unique combination of equipment was thosen to minimize machine traffic on the site in an attempt to reduce ground impacts on areas with sensitive soils or critical habitat concerns. The harvester was to fall and process all non-marked standing trees and process any solid stems on the forest floor into logs. A Koller K501 yarder (33ft tower), using a standing skyline, slackline system rigged with a tail tree and occasionally an intermediate support, was used to transport the logs to the landing. Production estimates obtained for the harvester and yarder were 7.33 cunits/PMH (20.74 m3/PMH1) and 5.41 cunits/PMH (15.31 m3/PMH) respectively. Actual system production was approximately three to four truck loads removed off the site on an average days with some days as low as two loads and some as high as six loads. An average truck load contained 5 Mbf (28.3 m3) or 24 tons (21.7 tonnes) of wood. Total logging cost for the system (stump to mill) was $78,809 which equated to $97/cunit ($34.24/m3) or $42.44/ton ($46.78/tonne) of material removed. On a per acre basis, the cost was $1 ,970/acre ($4869/ha). The presence of sawlogs in the unit allowed the landowner to make a profit from revenues of $103,258. Sawlogs made up 28% of the volume or 34% of the weight removed from the site but contributed 57% of the revenue generated. At the time of the study pulpwood prices were approximately $36/ton and sawlog prices were approximately $51 5/Mbf. The logging cost of $42.44/ton was greater than the value of the pulpwood and thus logging was made profitable by the presence of sawlogs. The thinning and salvage logging of a flat eastern Oregon stand with the combination of a single-grip harvester and small cable yarder proved to be reasonably cost efficient. The costs determined in this case study appear to be higher than traditiona' ground based methods of logging in similar terrain, but the cable system appears to have resulted in less soil impacts. Thus, in areas were soil protection is the most important consideration, this logging system may be a viable alternative to traditional ground based logging systems. Further research is recommended to evaluate potential improvements in the harvester - skyline system and to more fully compare this system with conventional skidding and forwarding systems, under the context of minimizing soil impacts.
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