Riparian buffer and density management influences on microclimate of young headwater forests of Western Oregon.

Abstract

Thinning of 30- to 70-year-old Douglas-fir (Psuedotsuga menziesii [Mirb.] Franco) stands is a common silvicultural activity on federal forest lands of the Pacific Northwest, United States. Empirical relationships among riparian functions, silvicultural treatments, and different riparian buffer widths are not well documented for small headwater streams. We investigated buffer width and density management effects on ripairan microclimates of headwater streams in Oregon. Spatial variations in stand density, canopy cover, and microclimate were measured along transects extending from stream center upslope into thinned stands, patch openings, or unthinned stands, with riparian buffers tanging from < 5 m up to 150 m width. For treated stands, summer mean daily air temperature maxima were 1 to 4°C higher than in unthinned stands. With buffers 15 m or greater width, daily maximum air temperature above stream center was less than 1°C greater, and daily minimum relative humidity was less than 5% lower than for unthinned stands. In contrast, air temperatures were significantly warmer within patch opening (+6 to +9°C), and within buffers adjacent to patch openings (+3°C) topographic slope breaks appear sufficient to mitigate the impacts of upslope thinning on the microclimate above headwater streams.

Citation

Anderson, Paul D.; Larson, David J.; Chan, Samuel S. 2007. Riparian buffer and density management influences on microclimate of young headwater forests of Western Oregon. Forest Science. 53(2): 254-269