Harvest pattern influences survival of forest-dependent species
The Demonstration of Ecosystem Management Options (DEMO) study was established in 1994 to evaluate the benefits of leaving some live trees standing as part of harvest treatments. The percentage of trees retained ranged from 15 to 100, and the retention pattern also differed among study sites in mature Douglas-fir forests.
Short-term results suggest that both dispersed and aggregated retention are needed to retain sensitive plants and animals, ameliorate harsh microclimatic conditions, and gain public acceptance of retention harvests. Although retention level had a greater influence on most ecological responses than did its pattern, retaining trees in aggregates of 2.5 acres provided several benefits over dispersed retention. Aggregates greatly reduced damage to and mortality of residual trees (particularly at lower retention levels) and provided short-term refugia for forest species sensitive to disturbance or environmental stress.
Based on these findings, a combination of aggregates larger than 2.5 acres and dispersed retention at levels considerably greater than current minimum standard of 15 percent appears a general strategy for ensuring the short-term persistence (and, presumably, the long-term recovery) of most forest-dependent species. It also appears to be an effective treatment for gaining public acceptance of green-tree retention that sustains the ecological and commodity values of managed forests. These studies have garnered international interest-both in the findings and in the safety and operational aspects of green-tree-retention harvests. Land managers in Pacific Northwest, British Columbia, and Tasmania have applied DEMO findings to forest management.
Forest Service Partners