Effects of logging debris treatments on five-year development of competing vegetation and planted Douglas-fir

Abstract

Although considerable research has focused on the influences of logging debris treatments on soil and forest regeneration responses, few studies have identified whether debris effects are mediated by associated changes in competing vegetation abundance. At sites near Matlock, Washington, and Molalla, Oregon, studies were initiated after timber harvest to quantify the effects of three logging debris treatments (dispersed, piled, or removed) on the development of competing vegetation and planted Douglas-fir (Pseudotsuga menziesii (Mirb.) Franco var. menziesii). Each debris treatmeat was replicated with initial and annual vegetation control treatments, resulting in high and low vegetation abundances, respectively. This experimental design enabled debris effects on regeneration to be separated into effects mediated by vegetation abundance and those independent of vegetation abundance. Two to three years after treatment, covers of Scotch broom (Cytisus scoparius (L.) Link) at Matlock and trailing blackberry (Rubus ursinus Cham. & Schltdl.) at Molalla were over 20% greater where debris was piled than where it was dispersed. Douglas-fir survival and growth did not differ among debris treatments when effects were evaluated independent of vegetation abundance (i.e., with annual vegetation control). suggesting negligible short-term effects of debris manipulation on soil productivity.

Citation

Harrington, Timothy B.; Schoenholtz, Stephen H. 2010. Effects of logging debris treatments on five-year development of competing vegetation and planted Douglas-fir. Canadian Journal of Forestry Research. 40: 500-510.