Comparative effects of precommercial thinning, urea fertilizer, and red alder in a site II, coast Douglas-fir plantation.

Abstract

We varied the number of red alder retained with 300 Douglas-fir per acre on a high-quality site in coastal Oregon. Alder densities of 0, 20, 40, and 80 per acre were tested. Our fifth treatment eliminated nitrogen-fixing alder, but substituted nitrogen fertilizer. Treatment 6 had neither thinning nor alder control. Treatments were randomly assigned within each of three blocks in a 9-year-old plantation. In pure Douglas-fir plots, gross volume growth was similar for nonfertilized plots, indicating no measurable benefits of additional nitrogen. In mixed stands, red alder reduced yield of associated Douglas-fir but not yield of combined species. Similar comparisons are needed at other locations, especially those with known nitrogen deficiency.

Citation

Miller, Richard E.; Obermeyer, Edmund L.; Anderson, Harry W. 1999. Comparative effects of precommercial thinning, urea fertilizer, and red alder in a site II, coast Douglas-fir plantation. Res. Pap. PNW-RP-513. Portland, OR: U.S. Department of Agriculture, Forest Service, Pacific Northwest Research Station. 25 p