Pacific Northwest Research Station

Title: Reducing stand densities in immature and mature stands, Applegate Watershed, Southwest Oregon.

Author: Main, Marty L.; Amaranthus, Michael P.

Date: 1996

Source: Res. Note PNW-RN-518. Portland, OR: U.S. Department of Agriculture, Forest Service, Pacific Northwest Research Station. 12 p

Station ID: RN-PNW-518

Description: Abstract Throughout the Applegate watershed, dense, overstocked, immature stands of mixed conifers and hardwoods and declining stands of mature conifers present significant and complex silvicultural problems. Stand stagnation is common, as is loss of large-diameter conifers from insects and wildfire. Treatments designed to maintain or encourage development of large-diameter conifers have not been tested. In this study, we examined conditions after density management treatments in two adjacent but dissimilar stands: (1) a dense, stagnant, immature stand of 40+-year-old hard-woods and conifers, and (2) a stand of declining mature conifers over a rapidly encroaching understory of hardwoods and conifers. The immature stand received a unique density-reduction treatment retaining both hardwoods and conifers to encourage long-term survival and growth of its coniferous component. The density-reduction treatment in the mature stand focused on removal of the competitive influence from overstocked, suppressed understory trees and maintaining existing large-diameter conifers. Precommercial thinning greatly reduced stand density and increased quadratic mean diameters in the immature stand. Before precommercial thinning, Pacific madrone (Arbutus menziesii Pursh) dominated, even though it regenerated at the same time as Douglas-fir (Pseudotsuga menziesii (Mirb.) Franco). Following precommercial thinning, relatively equal numbers, sizes, and basal areas of Douglas-fir and madrone were retained. Several light thinnings may be necessary to foster development of vigorous Douglas-fir that can release and ultimately grow into large-diameter mature trees. In the mature stand, the combination of commercial and precommercial thinnings produced a reduced stand density designed to improve overall stand vigor. Trees per acre and basal area were greatly reduced in all diameter classes less than 24 inches but were not reduced in diameter classes greater than 24 inches.

Keywords: Applegate watershed, basal area, commercial thinning, competition, Douglas-fir, large-diameter conifers, Pacific madrone, precommercial thinning

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Citation

Main, Marty L.; Amaranthus, Michael P.  1996.  Reducing stand densities in immature and mature stands, Applegate Watershed, Southwest Oregon..   Res. Note PNW-RN-518. Portland, OR: U.S. Department of Agriculture, Forest Service, Pacific Northwest Research Station. 12 p