Productivity and costs of an integrated mechanical forest fuel reduction operation in southwest Oregon

Forest Products Journal, Mar 2009 by Bolding, M Chad, Kellogg, Loren D, Davis, Chad T

Abstract

Mechanical forest fuel reduction treatments that harvest and extract small, non-merchantable trees are often integrated into commercial thinning operations. Harvesting system feasibility and/or costs from such operations has been sparsely reported in the literature. To broaden the knowledge of mechanical approaches of harvesting and utilizing small trees, this study assessed the productivity and cost from an integrated forest harvesting/mechanical forest fuel reduction operation in southwest Oregon. The study was conducted in a fuel reduction thinning of a 20-acre mixed conifer stand on gentle terrain. A tracked swing-boom feller-buncher, two rubber-tired grapple skidders, a swing-boom grapple processor, an in-woods chipper, and a tub grinder were used to fell, extract, and process non-merchantable stems and limbs and tops from felled merchantable trees into fuel (energy-wood) chips. Thinned merchantable trees were also extracted and processed into log lengths. Results indicate that harvesting and processing non-merchantable trees increased total costs by $1,193.43 per acre. From a biomass harvesting perspective, removing only the non-merchantable portion of the stand would have resulted in a net cost of $968.96 per acre. Thinning merchantable trees added value to the operation, subsidized costs, and decreased the net loss by $872.00 per acre, resulting in a net cost of $96.96 per acre.

Forested landscapes, specifically in the Western United States, have changed greatly since European settlement. Many presettlement forests were characterized by a large mature overstory with a sparse and mostly open understory (Weaver 1959). It has been reported that these conditions occurred largely due to frequent burning by indigenous people (Kimmerer and Lake 200 1 ). In the years since European settlement, human impact on forest structure and composition is evident (Harvey et al. 1995, Brose et al. 2001). Anthropogenic influence, such as fire exclusion, has caused public lands in the United States to become severely overstocked with small stagnant trees. The U.S. Forest Service (2005) reported that at least 28 of a total 236 million acres of forestland in the 15 western states could benefit from fuel reduction treatments. O'Laughlin and Cook (2003) indicated that National Forests in the United States are on average 50 percent denser than forests in any other ownership. Overall, forests in the Pacific Northwest region contain more live-tree biomass than any other U.S. region (Woodall et al. 2006).

Small trees, tightly spaced in the understory of mature forests, inherently increase wildfire hazards. The small trees provide a ladder for surface fires to reach the overstory crown and can result in stand-replacement wildfires by promoting fire spread. Laverty and Williams (2000) report that fire suppression activities have caused public lands to over-accumulate shrubs and small trees which "reduce ecosystem diversity, health, resiliency, and fuel conditions for unnaturally intense fires." These effects are particularly important for stands with histories of frequent low intensity fire. The over-accumulation of small trees and understory vegetation has changed some fire regimes from low intensity to high severity allowing crown fires to occur in forest types not historically prone to such occurrences (Mutch et al. 1993, Brown et al. 2004).

Given the current forest health and wildfire hazard situation on many forests in the Western United States, research is needed to address methods of managing vegetation structure for the purpose of producing more fire resilient landscapes. There is ample opportunity and much interest in employing precommerciai thinning that could alleviate the overstocking problem along with wildfire hazard. Such a proactive approach to fuel management may produce less monetary and environmental cost than fire suppression and stand replacement (Lynch 2004). With these observations, it is imperative that fuel reduction activities be investigated in attempts to protect the forest resource along with its associated assets, both market and non-market (Mason et al. 2006).

Commercial fuel reduction activities can be defined as operations with an end goal of changing forest fuel structure while extracting fiber in hopes of producing utilizable wood products that can be sold to finance fuel reduction treatments (Bolding 2006). Hollenstein et al. (2001) explained that mechanical harvesting differs from other methods of fuel reduction, especially prescribed fire, in that "removal is immediately effective, does not result in air pollution or escaping fires, and may be economically self-sustaining." They also report that reducing fuel loads through thinning could slow stand-replacement fire occurrences.

As the need and justification for vegetation removal through thinning of overstocked stands has grown, commercial systems have been used to harvest small-diameter, nonmerchantable trees. This approach to forest fuel reduction poses many challenges to the forest manager. The majority of mechanized logging equipment is designed to fell and extract trees large enough to produce revenue. These machines are typically not configured to productively fell, process, and extract small trees (Bolding 2002). In economic terms, mechanical thinning is problematic due to the fact that harvesting small stems is expensive and the resulting wood product has low value, producing high harvesting costs per unit or area (Watson et al. 1986, Bolding and Lanford 2005). Also, few cost and productivity estimates have been developed for mechanical fuel reduction/small wood harvesting systems (Bolding and Lanford 2001, Coulter et al. 2002). STHarvest (Hartsough et al. 200 1 , Fight et al. 2003) and the Fuel Reduction Cost Simulator (FRCS) (Fight et al. 2006) are cost models that have been used to predict relative costs for harvesting small trees. These models, however, are driven by production equations from older machine studies of conventional equipment and are not specifically geared toward treatments that often require harvesting small trees to diameters of 1 inch. Extrapolation beyond the range of reliable data can often lead to extreme variation in cost estimates. This observation highlights the need for additional research on systems that specifically target small, non-merchantable trees commonly extracted in fuel reduction applications.