Thinning and riparian buffer configuration effects on down wood abundance in headwater streams in coniferous forests

Abstract

Down wood is associated with the function, structure, and diversity of riparian systems. Considerable knowledge has been generated regarding down wood stocks and dynamics in temperate forests, but there are few studies on effects of silvicultural practices and riparian buffer design on down wood, particularly in headwater streams. We analyzed interactive eff ects of upland thinning and riparian buffer configuration on down wood volumes and decay classes at fi ve managed forest sites in western Oregon. We tested the eff ects of two thinning treatments—an unthinned control and a moderate-density thinning with 200 trees ha-1—and three riparian buff er widths: combined one and two site-potential tree heights (to 480 ft [146 m]); variable-width (50 ft [15.2 m] minimum); and streamside retention (~20 ft [6 m]), in coniferous stands dominated by Pseudotsuga menziesii and Tsuga heterophylla. Pre-harvest down wood volumes (59 to 128 m3∙100 m-1 reach length) in 29 stream reaches (193 to 792 m long) did not diff er among thinning treatments and stream buff er confi gurations. One year after thinning, down wood volumes were 5–42 percent greater than pre-harvest levels, although thinning and stream buffer effects remained non-significant. Large increases in down wood volumes with time in our headwater streams may be the consequence of severe storms or other events not directly related to silvicultural practices.

Parent Publication

• Density management in the 21st century: west side story

Citation

Ares, Adrian; Olson, Deanna H.; Puettmann, Klaus J. 2013. Thinning and riparian buffer configuration effects on down wood abundance in headwater streams in coniferous forests. In: Anderson, P.D.; Ronnenberg, K.L., eds. Density management in the 21st century: west side story. Gen. Tech. Rep. PNW-GTR-880. Portland, OR: US Department of Agriculture, Forest Service, Pacific Northwest Research Station: 210-210.