Arthropod Diversity and Conservation in Old-Growth Northwest Forests

Old-growth forests of the Pacific Northwest extend along thecoastal region from southern Alaska to northern California andare composed largely of conifer rather than hardwood tree species.Many of these trees achieve great age (500–1,000 yr).Natural succession that follows forest stand destruction normallytakes 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 time,combined with the many different plant species that characterizesuccession, results in an array of arthropod habitats. It isestimated that 6,000 arthropod species may be found in suchforests—over 3,400 different species are known from asingle 6,400 ha site in Oregon. Our knowledge of these speciesis still rudimentary and much additional work is needed throughoutthis vast region. Many of these species play critical rolesin the dynamics of forest ecosystems. They are important innutrient cycling, as herbivores, as natural predators and parasitesof other arthropod species. This faunal diversity reflects thediversity of the environment and the arthropod complex providesa sensitive barometer of the conditions of the forest. Conservationefforts for forest arthropods are limited at present and controlledlargely by land-use policies. For example, an effort is beingmade to include arthropods in conservation efforts for the NorthernSpotted Owl and arthropods will be included in the Forest HealthMonitoring program now underway by the U.S. Forest Service.Evidence from other parts of the world suggest that arthropodsthat depend upon large pieces of dead wood may be particularlythreatened by forest management practices. Much remains to bedone in the conservation of forest arthropods.