The Use of Mechanical Thinning Treatments in Management of Small Stands at the Wildland Urban Interface

Abstract

This study analyzed the productivity and costs of mechanical thinning at the Wildland Urban Interface (WUI). It compared conventional commercial first thinning practices in even-aged loblolly pine plantations in the Southeast US to alternative mechanical thinning treatments with more intense removals intended to promote transition to uneven-aged stand management. Production data of harvesting operations were collected at six harvesting sites in Alabama, Georgia, and Mississippi, USA. The harvesting system of all sites employed 1 feller-buncher, 1 wheeled skidder and 1 knuckleboom loader, and 3 or 4 crew members. Elemental time study information was collected on the skidder and on the feller-buncher using a portable video camera system, and work sampling technique was applied to the loader. Regression of the time study data indicated no treatment difference for skidder and feller-buncher cycle time. Skid distance and bunch size variables most significantly affected skidder cycle time. Increases in these variables increased skidder cycle time. For the feller-buncher, the number of trees per accumulation and thinning method significantly affected cycle time. Selection within leave rows and larger accumulations resulted in longer cycles. Loader utilization was affected by treatment and was higher for the heavy removal. Costs analysis was completed for three potential thinning treatments, conventional, heavy, and patch treatments. Harvest costs were compared for three of the six study sites and for three stand sizes (4, 8, and 12ha). Increased stand size reduced costs by lowering fixed costs per unit of move in and set up activities. Treatment differences were greatest for the 4ha stand, where the greatest gain in residual value was observed. Site differences influenced harvesting residual values through wood product value (proportion of pulpwood and chip and saw) and total volume harvested. The results of this study indicated a potential benefit for landowners from the alternative mechanical treatments. The greater volume removed by the alternative treatments resulted in significant gains in residual values. Increased residual values make small tracts more marketable for landowners and more attractive to buyers and loggers.