ARTHROPOD DIVERSITY AND CONSERVATION IN OLD-GROWTH NORTHWEST FORESTS

Old-growth forests of the Pacific Northwest extend along the coastal r egion from southern Alaska to northern California and are composed lar gely of conifer rather than hardwood tree species. Many of these trees achieve great age (500-1,000 yr). Natural succession that follows for est stand destruction normally takes over 100 years to reach the young mature forest stage. This succession may continue on into old-growth for centuries. The changing structural complexity of the forest over t ime, combined with the many different plant species that characterize succession, results in an array of arthropod habitats. It is estimated that 6,000 arthropod species may be found in such forests-over 3,400 different species are known from a single 6,400 ha site in Oregon. Our knowledge of these species is still rudimentary and much additional w ork is needed throughout this vast region. Many of these species play critical roles in the dynamics of forest ecosystems. They are importan t in nutrient cycling, as herbivores, as natural predators and parasit es of other arthropod species. This faunal diversity reflects the dive rsity of the environment and the arthropod complex provides a sensitiv e barometer of the conditions of the forest. Conservation efforts for forest arthropods are limited at present and controlled largely by lan d-use policies. For example, an effort is being made to include arthro pods in conservation efforts for the Northern Spotted Owl and arthropo ds will be included in the Forest Health Monitoring program now underw ay by the U.S. Forest Service. Evidence from other parts of the world suggest that arthropods that depend upon large pieces of dead wood may be particularly threatened by forest management practices. Much remai ns to be done in the conservation of forest arthropods.