Pacific Northwest Research Station

PNW > Research > Large Scale Siviculture Experiments > Density Management Study, Initial Thinning

Large-Scale Silvicultural Experiments In Western Oregon and Washington

Density Management Study, Initial Thinning

Initial Installation Years: 1996-2000

Primary Objectives: Evaluate effects of alternative forest density management treatments on important stand and habitat attributes in previously unthinned stands. Determine treatment effects on selected plant and animal taxa. Use these sites to develop operational approaches to implementation of new prescriptions, improve methods for effectiveness monitoring of plant and animal taxa, and to share results of on-the- ground practices and findings with land managers, regulatory agencies, policymakers, and the public.

Pre-treatment Conditions: 50- to 70-year-old stands.

Locations: Bottom Line (43.7722°N, 123.2364°W), Delph Creek (45.2656°N, 122.1592°W), Green Peak (44.3667°N, 123.4583°W), Keel Mountain (44.5281°N, 122.6319°W), North Soup (43.5658°N, 123.7772°W), OM Hubbard (43.2916°N, 123.5833°W), and Ten High (44.2806°N, 123.5183°W).

Initial Treatments: 3 thinning treatments and 1 unthinned control each replicated 1 time at 7 locations.

No Overstory Removal (Control)

Unthinned Control (1a). Not thinned. Underplanted nine 1-acre areas with western hemlock and western redcedar. No woody debris or other initial treatments.

Light Overstory Removal

High Density Retention (2a). Thinned 70-75% of stand to 120 tpa. Left 20-30% of stand as riparian buffers and/or leave islands of three sizes (0.25, 0.5, and 1.0 acres). Underplanted nine 1-acre areas with western hemlock and western redcedar. No woody debris or other initial treatments.

Moderate Overstory Removal

Moderate Density Retention (3a). Thinned 60-65% of stand to 80 tpa. Cut 10% of stand to create circular gaps (0.25, 0.5, and 1.0 acres). Left 10% of stand in circular leave islands (0.25, 0.5, and 1.0 acres). Left 15-20% of stand as unthinned riparian buffers. Underplanted nine 1-acre areas with western hemlock and western redcedar. Planted gaps with western hemlock, Douglas-fir, western redcedar, and grand fir. No woody debris or other initial treatments.

Variable Density Retention (3b). Thinned 10% of stand to 40 tpa, thinned 25-30% of stand to 80 tpa. Thinned 25-30% of stand to 120 tpa. Cut 10% of stand to create circular gaps (0.25, 0.5, and 1.0 acres). Left 10% of stand in circular leave islands (0.25, 0.5, and 1.0 acres). Left 15-20% of stand as unthinned riparian buffers. Planted gaps and underplanted 40 tpa overstory areas with western hemlock, Douglas-fir, western redcedar, and grand fir. No woody debris or other initial treatments.

Heavy Overstory Removal

None.

Complete Overstory Removal (Clearcut)

None.

Response Variables: Over-, mid-, and understory vegetation; lichens, mosses, and bryophytes; birds; arthropods; amphibians; mollusks; snags; woody debris; fungi; microclimate; forest floor.

Study Plan: Cissel, J.H.; Anderson, P.D.; Berryman, S.; Chan, S.S.; Olson, D.H.; Puettmann, K.J.; Thompson, C. 2006. BLM Density Management and Riparian Buffer Study: establishment report and study plan. Scientific Investigations Report 2006–5087. Reston, VA: U.S. Department of the Interior, Geological Survey. 144 p.

Website: http://ocid.nacse.org/nbii/density/

(last accessed 2006-12-06)

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USDA Forest Service - Pacific Northwest Research Station
Last Modified:  Tuesday, 29 January 2008 at 17:10:55 EST