PARENT SESSION
Oral Session # 97: Restoration Ecology II: Rivers and Forests.
Presiding: J Weishampel
Friday, August 8. 8:30 AM to 12:00 PM, SITCC Meeting Room 203.

Restoring biocomplexity in Douglas-fir forests: Understory development after inducing canopy heterogeneity and underplanting tree seedlings.

Aukema, Juliann^*,1, Carey, Andrew¹, ¹ Pacific Northwest Research Station, Olympia, WA, USA

ABSTRACT- Ancient forests have become prominent in conservation issues in North America, in part because of their value as habitat for threatened species and reservoirs of biological diversity. In the Pacific Northwest, the northern spotted owl is a symbol of the conflict between conservation values and economic values associated with old-growth Douglas fir forests. Today, early successional forests make up nearly half of Federal forested lands in the Pacific Northwest. The Forest Ecosystem Study is an experiment in using variable density thinning (VDT), to induce spatial heterogeneity in forest canopies, and underplanting of shade tolerant tree seedlings, to restore tree species diversity, with the goal of accelerating development of second-growth forests into forests with some of the characteristics (e.g. structural, biological diversity) of old, natural forests. We conducted this study in two forests with different management histories (commercial and legacy). We examined the survival and growth of underplanted Abies grandis (grand fir), Thuja plicata (western redcedar), Pinus monticola (western white pine), and Alnus rubra (red alder) in experimentally thinned stands, and composition and cover of understory vegetation in both thinned and unthinned stands. We found that forest management history had the greatest effect on seedling survival and growth and on understory vegetation. Survival of seedlings and understory vegetation was not directly correlated with thinning intensity or overstory canopy. This is probably because the influence of canopy gaps is displaced due to the low sun angles in this region. Variable density thinning in conjunction with other conservation measures may accelerate biocomplexity in second-growth forests and holds promise for providing a full range of ecological services and economic goods.

Key words: Douglas fir forest management, variable density thinning, understory, tree underplanting