(by Michael Gallagher – Science and Technology Committee)
Although this study took place in forests different in composition than those of New Jersey, this study provides the framework by which to plan integrated harvesting for fuel reduction, and some values by which to estimate cost effectiveness.
Thinning forests can be a useful alternative to prescribed burning for fuel reduction, especially when social, economic, or administrative issues limit the use of prescribed fire, or where fire exclusion has left a stand susceptible to undesirable damage from fire. Fuel reduction thinning removes ladder fuels, typically shrubs and small trees, reducing the potential for subsequent surface fire to transition to the canopy. In addition to reducing the danger of high-intensity wildfire, thinning may additionally provide ecological benefits. Compared to prescribed burning, however, thinning is often substantially more expensive and typically only removes small trees below size and quality limits for sawlogs, making it difficult offset costs with this form of fuel reduction managements.
Researchers from Humboldt State University and the Rocky Mountain Research Station recently studied the cost effectiveness of an integrated harvesting method, incorporating both sawlog and smaller sized trees, and provide useful estimates of costs for different aspects of the operation. The study took place on a 55-ac thinning unit on the Klamath National Forest, on the California-Oregon border in a mixed conifer forest (white fir, Douglas-fir, ponderosa pine, incense cedar, and sugar pine). Prior to harvesting, sawlog sized trees made up 97% of the stand volume with a basal area of 257ft2/ac, whereas smaller trees had a basal area of 14.7ft2/ac yet accounted for 45% of the stand density (106 trees/ac). Over 10 12-hour days several feller-bunchers and extraction machines removed an estimated 2,243ft3/ac of sawlog sized biomass and 198ft3/ac of smaller tree biomass, or 25% of sawlog timber and 95% of smaller trees. Sawlogs were sold for dimensional timber, and smaller trees were chipped and sold as softwood biomass.
Ladder fuels were significantly reduced with canopy bulk density dropping from 0.0055 to 0.0036 lb/ft3 and canopy base height increasing from 19 to 45ft. Sawlog felling accounted for approximately 29% of sawyer time, with smaller tree felling accounting for the remainder. Time budgets and costs for specific equipment were also provided. Unit production cost for sawlogs was $0.42/ft3 and for smaller trees was $52.41/bone dry ton (BDT). Prices of delivered softwood biomass were less than production cost, ranging from $34 to $51 per BDT.
The researchers found that integrated harvesting system cost effectively reduced fuels. However success of such an operation ultimately hinges on the balance of sawlog and small tree biomass harvested, as well as optimization of equipment use to minimize on the job down time. Skidding was an important bottleneck in the operation, and skidding distance was an important variable cost. Tables describing the costs of various types of machinery, a standardized skidding unit production cost table, and a mathematical formula for estimating equipment time are available in the full text version of the study.
For the full text article, visit: http://www.forestprodjournals.org/doi/pdf/10.13073/0015-7473-61.8.664