The US Forest Service (USFS), Pacific Northwest Research Station (PNW), and Oregon State University (OSU) established the Young Stand Thinning and Diversity Study (YSTDS) in 1990 to demonstrate and test options for young stand management in western Oregon. The YSTDS is designed to determine if different thinning, underplanting, and snag creation treatments can accelerate the development of late-seral conditions in 35-50 year-old plantations.
The study was implemented on 4 replicate blocks, each consisting of an untreated Control stand and 1 each of the following stand-level thinning treatments: (1) a Light Thin treatment, approximating the timber industry standard, with about 260 residual trees per hectare (tph; 100/acre); (2) a Heavy Thin treatment leaving approximately 130 tph (50/acre) and underplanted with native conifer seedlings; and (3) a Light Thin with Gaps (hereafter simply “Gaps”) treatment, again with 260 tph plus an additional 20% of the stand area harvested to leave 0.2 ha (0.5-acre) openings underplanted with native conifer seedlings.
Pre-thinning baseline data (documenting vegetation, fungi, wildlife, and photopoints) were gathered in 1992-1994, and the thinning treatments were implemented through timber sale contracts from late 1994 through early 1997, with most logging occurring during 1995-96. During the thinning harvests, detailed analyses were carried out to examine pre-sale planning and layout costs, comparative productivity and costs of various harvesting alternatives, residual stand damage, and soil disturbance and compaction. A considerable body of publications on these operational aspects of the YSTDS constitutes one of the largest portions of the study’s results so far.
Much science has been accomplished in the 15 years since the YSTDS thinning treatments were installed. Vegetative response to the thinning has been measured at frequent intervals, in 1996, 1999, 2001, and 2006. Changes in volumes of coarse woody debris and the responses of fungi, arthropods, amphibians, birds, and small mammals have also been assessed, and are intended to continue into the future. Five years after thinning (2001), snag densities in the YSTDS were artificially increased by topping trees and inoculating some with fungal mycelia, in an effort to increase the abundance of dead trees for cavity-nesting birds and mammals; long-term monitoring of these artificial snags is underway. The study also included a social science component exploring the public’s response to visual changes in the forest from the thinning operations.
Brenda C McComb, Joan C. Hagar, Matthew G. Hunter, Steven L. Garman, Tom Manning
Understanding how to maintain the ecological diversity of young managed stands is a topical issue in forest management in the Pacific Northwest region. To begin to understand the effects of different thinning treatments on ecological diversity, the Willamette National Forest initiated the Young Stand Thinning and Diversity study (YSS). This study compares relative populations of small mammals, amphibians, and birds under different thinning treatments. Tree growth and vegetation development are also examined.