Gabriel F. Tucker, Forest Management Consultant, Olympia, WA
Several recently established up-slope Pacific Northwest
thinning studies were selected based on their innovative treatments, replicated
and randomized experimental design and interdisciplinary approach. These projects include:
1. Alternative
Silviculture in Young Plantations
2. Commercial
Thinning for Diversity
3. Density
Management Studies
4. Forest
Ecosystem Study
5. H.J. Andrews
Experimental Forest Uneven-Aged Management Study
6. Influence of Snag Creation and Thinning
on Stand Structure and Wildlife Abundance and Diversity
7. Olympic
Habitat Development Study
8. Silvicultural
Options for Harvesting Young-Growth Production Forests
9. Two-Storied
Management in Young Stands
10.
Young Stand Thinning and Diversity Study
The age of the studied stands varied widely but the most were at the time of the first commercial thinning at 30 to 50 years of age. Most project objectives involved examining, at least the short-term impacts of thinning and how it and other treatments, such as underplanting and snag creation, could lead to enhanced structural and species diversity. Long-term objectives are not always addressed, although some projects examine silvicultural systems, which entail an ongoing series of treatments. Research findings to date are generally limited, due the early stage that all studies are in, although vascular plant diversity has been shown to increase relatively rapidly and several important relationships have been presented between levels of overstroy retention and the response of understory vegetation. The above projects are also compared to related riparian studies, historic or retrospective studies as well as several harvest-level studies. The geographic coverage of the ten thinning studies includes much of Oregon and Washington with the largest exception being the central and northern Washington Cascades. To cover new areas or to involve additional treatments such as variable density thinning as opposed to more traditional evenly distributed thinning, land managers may consider installing one or more replications of a series of treatments from a previously established project. Such an approach could be more economical and reduce the time required for installation.
Keywords: thinning, studies, diversity.