Title: Variable-retention harvests in the Pacific Northwest: a review of short-term findings from the DEMO study
Author: Aubry, Keith B.; Halpern, Charles B.; Peterson, Charles E.
Source: Forest Ecology and Management
doi: 10.1 016/j.foreco.2009.03.013
Description: In the Pacific Northwest (PNW) region of the contiguous United States, retention of live (green) trees in harvest units is an integral part of forest management practices on federal lands, yet the ecological benefits that result from various levels or patterns of retained trees remain speculative. The Demonstration of Ecosystem Management Options (DEMO) study was established to address these informational gaps. The experimental design consists of six treatments, each 13 ha in size, replicated at six locations (blocks) in western Washington and Oregon. Treatments represent strong contrasts in retention level (15-100% of original basal area) and pattern (trees dispersed vs. aggregated in 1-ha patches) in mature Douglas-fir (Pseudotsuga menziesii) forests. A wide variety of ecological responses and public perceptions of visual quality have been examined; this paper provides a comprehensive review of the short-term (1-7 years) results of these studies. Level of retention had a strong effect on many responses. At 15% retention, regardless of pattern, microclimate, ecological responses, and public perceptions of visual quality did not differ from those measured in the "clearcut" areas of aggregated treatments. In contrast to level of retention, pattern of retention had limited effect on most measures of biological response. Collectively, our findings suggest that retention levels > 15% are needed to effectively retain sensitive plants and animals, ameliorate harsh microclimatic conditions, and gain public acceptance of retention harvests in these forests. A combination of relatively large (>1 ha) aggregates and dispersed trees at levels considerably greater than current minimum standards in the PNW may be the most effective strategy for sustaining a broad array of forest values in managed stands.
Keywords: aggregated retention, biological responses, dispersed retention, forest structure, green-tree retention, refugia, public perceptions
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Aubry, Keith B.; Halpern, Charles B.; Peterson, Charles E. 2009. Variable-retention harvests in the Pacific Northwest: a review of short-term findings from the DEMO study. Forest Ecology and Management. 258: 398-408.
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