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Pacific Northwest Research Station
Large-Scale Silvicultural Experiments In Western Oregon and Washington
Initial Installation Years: 1994-1995
Primary Objectives: Evaluate short- and long-term growth and yield of overstory trees, stand differentiation, and variation in horizontal and vertical structure in response to alternative silvicultural prescriptions. Monitor short- and long-term population responses of small mammals, birds, amphibians, and vascular plants to the implementation of alternative silvicultural prescriptions. Accelerate the development of characteristics associated with late-successional forests.
Pre-treatment Conditions: 10- to 13-year-old, even-aged Douglas-fir plantations.
Locations: Clearwater Study (CWS; 46.2560°N, 121.9980°W) and Very Young Stand Management Study (VYSMS; 44.2528°N, 122.2064°W).
Initial Treatments: 4 thinning x planting treatments and 1 unthinned control each replicated 5 times at the CWS location and each 1 time at the VYSMS location.
No Overstory Removal (Control)
Treatment A: untreated control (1a). Provide a comparison between rates of stand development and differentiation with and without post-planting treatments. Not thinned. Not planted. No woody debris or other initial treatments.
Light Overstory Removal
Moderate Overstory Removal
Treatment B: thinned (no gaps), not planted (3a). Emphasize uniformity of species composition and stand structure with a long-term goal of high-value wood production. Thinned 100% of stand uniformly to 340 tpa by removing alternate diagonal rows. Not planted. No woody debris or other initial treatments.
Heavy Overstory Removal
Treatment C: thinned (1 gap size), planted (4a). Increase tree species diversity without making major changes in uniformity of tree spacing. Thinned 100% of stand uniformly to 340 tpa by removing alternate diagonal rows. Removed additional 100 tpa to create eight uniformly distributed 42 ft x 42 ft (0.04 acre) gaps per acre. Planted with 100 tpa red alder in gap centers. Planted 40 tpa western hemlock and 40 tpa western redcedar on the gap edges. Planting was not as uniform as the treatment descriptions imply. No woody debris or other initial treatments.
Treatment D: thinned (3 gap sizes), not planted (4b). Increase structural heterogeneity. Treatment is designed to increase horizontal and vertical diversity (spatial heterogeneity) in the stand. Thinned 100% of stand uniformly to 340 tpa by removing alternate diagonal rows. Removed additional 100 tpa to create three different sized gaps: 16 ft x 28 ft, 28 ft x 42 ft, and 42 ft x 42 ft. Not planted. No woody debris or other initial treatments.
Treatment E: thinned (3 gap sizes), planted (4c). Increase species, vertical and horizontal diversity. Treatment is an attempt to accelerate the development of conditions associated with old-growth forests through intensive silviculture. Thinned 100% of stand uniformly to 340 tpa by removing alternate diagonal rows. Removed additional 100 trees/ac to create three different sized gaps: 16' x 28', 28' x 42', and 42' x 42'. Selected 30 large and vigorous trees/ac for growth enhancement. Kept 20 tpa of the growth enhancement trees in an open-grown situation to maximize growth. Planted 50 tpa red alder (7 ft x 7 ft spacing) in 28 ft x 41 ft and 41 ft x 41 ft gaps. Planted 75 tpa western hemlock and 75 tpa western redcedar (6 ft x 6 ft) in all three sized gaps. Planting was not as uniform as the treatment descriptions imply. No woody debris or other initial treatments.
Complete Overstory Removal (Clearcut)
Response Variables: Over-, mid-, and understory vegetation; mosses; snags; woody debris; climate; wood production; economics; forest floor.
Study Plan: Crisafulli, C.M.; Harrington, C.A. 1994. Alternative silviculture in young Douglas-fir plantations: effects of stand composition and structure on plant and animal populations and on the production of forest products. Study plan. On file with: C. Harrington, U.S. Department of Agriculture, Forest Service, Pacific Northwest Research Station, Olympia Forestry Sciences Laboratory, 3625 93rd Avenue SW, Olympia, WA 98512.
(last accessed 2006-12-06)
US Forest Service - Pacific Northwest Research Station