Intensive management influence on Douglas-fir stem form, branch characteristics, and simulated product recovery

Abstract

Intensive management may adversely affect lumber yield and quality by increasing knot size and creating a more conical stem form with a greater average rate of taper. This study was initiated to examine the impact of management on simulated lumber yield and quality. Stem diameter and branch size and location of 223 Pseudotsuga menziesii (Mirb.) Franco (Douglas-fir) stems ranging in age from 5 to 65 years and from a wide variety of stand conditions were intensively measured. Stand conditions included varying levels of vegetation management, precommercial thinning, commercial thinning, fertiliser application, and severity of infection by Phaeocryptopus gaeumannii (Rohde) Petrak (Swiss needlecast). In addition, 86 virtual logs were created and processed by AUTOSAW. Significant changes in both stem form and branch characteristics were observed among the stand conditions examined, with maximum branch size being the most responsive to silvicultural regime and disease severity. Changes related to fertilizer and thinning were not significant enough to adversely affect simulated lumber quality and yield. Indices of branch size were poor predictors of simulated log grade yield. Although quantification of branch size and location is important for understanding crown structure, growth potential, and the vertical distribution of biomass, factors such as juvenile wood percentage and wood density may exert more control over simulated product quality in the young Douglas-fir analysed in this study.

Citation

Weiskittel, A.R.; Monserud, R.A.; Rose, R.; Turnblom, E.C.; Maguire, Douglas A. 2006. Intensive management influence on Douglas-fir stem form, branch characteristics, and simulated product recovery. New Zealand Journal of Forestry Science. 36(2/3): 293-312