Funded Research Projects: FOREST ECOLOGY

Long-term responses of vegetation to variable-retention harvests

Research Sponsored By: US Forest Service
Principal Investigator: Charles Halpern
Project Description
Variable-retention harvest is a key component of ecological forestry worldwide. It involves the retention of major forest structural elements (live trees, snags, and logs) through timber harvest to emulate the outcomes of natural disturbance. The goals of retaining live overstory trees within harvest units include moderation of the understory microclimate, structural enrichment of the regenerating forest, and "lifeboating" of forest-dependent species through disturbance. To what extent level and spatial pattern of overstory retention can be manipulated to achieve these goals remains an important question in many forest ecosystems. The Demonstration of Ecosystem Management Options (DEMO) Study was established in 1993 to examine the responses of diverse groups of forest organisms to variable-retention harvest of mature Douglas-fir forests in the Pacific Northwest. It comprises six experimental treatments with contrasting levels and patterns of retention replicated at each of six locations in western Oregon and Washington. It is the only such experiment in this region, providing a critical test of current federal standards and guidelines for regeneration harvests. An extensive array of permanent sample plots facilitate periodic assessments of the structural and biodiversity values of these experimental treatments. The supplemental funding provided by this cost-reimbursable agreement will support a 17- to 18-year remeasurement of these plots with a focus on patterns of tree regeneration and their relationships to overstory structure.