Increasing Aspen Production through Mechanical Strip-Thinning (December 1, 1991-May 31, 1992): Monitoring Report

Abstract

Progress on five major research tasks is highlighted including studies of the effects of stripthinning of aspen on growth and disease. Economic analyses and collection of cost data are also a part of this project. Recently-established field tests of strip-thinning show that stands respond relatively quickly to strip-thinning. Average growth rates increased by approximately 15 percent over unthinned stands in the two years following thinning. Measurement plots in these studies were permanently-monumented during the reporting period to allow relocation of plots after the project is completed. Studies done as part of Task II show that a significant relationship exists between the average tree size and stand density in the aspen stands in our experiment network. This relationship provides a practical means to quantify stand density relative to that of the average aspen stand and will be used in the formulation of management recommendations. These studies also showed a significant relationship between the average stocking density in our stands and the density inherent in the published normal yield table for aspen. This relationship provides a basis from which to project wood yields through time. In cooperation with Boise Cascade and Blandin Paper Company, Division of Lands and Forestry, plans are being made to develop a more accurate tool to assess site productivity for aspen. Measurements of previously-thinned stands on the Chippewa National Forest showed variation in the response to thinning. One stand has more than two times the merchantable volume in a thinned area compared to an unthinned area while the other shows little response to thinning. Disease analyses have included notation of disease and stand condition on all sites. No difference in disease incidence is evident between thinned and unthinned stands at this time. Cost data recently collected from an operational-scale thinning trial showed costs ranging from $6.75 to $8.90 per acre with an average cost of approximately $8.00 per acre. Due to optimal site conditions, these costs are likely near the low end of the cost range for strip-thinning. Technical assistance was provided to the Blandin Paper Company, Division of Lands and Forestry during the reporting period. Current research status and economic analyses were provided to assist in future land management planning.