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生物多様性セミナー 2004年10月

Influence of natural disturbance upon landscape configuration of old forest in the Americas: Application of these ideas toward conservation strategies in Asia.

Kenneth Parker (AIRIES Visiting scholar)


Conservation of plant and animal species continues to be an uphill battle amid continued pressures from human population growth and diminished habitat. Among forest ecosystems, species from old forest are at greater risk of extinction because these elements of the landscape are not readily regained once removed. We studied the configuration of old forest as influenced primarily by fire in forests of western North America. We measured the distribution of bird species in forests of the Central Interior Plateau of British Columbia where frequent wildfires historically created large areas of even-aged forest with isolated patches of unburned older forest. Using point counts and transects, bird species were sampled in two types of forest: 60 − 80 year old burns containing remnant patches amid a successional matrix of lodgepole pine, and large patches of old-growth forest originating through exclusion between different wildfires. The patches comprising 10 − 15% of the burn area ranged from 0.030 to 20 ha. Old forest exceeded 100 ha. Canopies in the patches and old forest consisted of hybrid white spruce and lodgepole pine (mean age, 200 years). Bird counts were higher in old forest than patches, and both were higher than the intervening matrix forest. Nearly all bird species found in old and matrix forest also occurred in the patches but 15 were more abundant in old forest. Only 1 species (black-backed woodpecker) was decidedly more abundant in small patches, and 2 species in matrix forest, than old forest. Upland patches larger than ~6 ha contained as many species per unit of search as the larger old forests. Harvesting regimes and other land use regimen that simulate these patterns of natural disturbance should support richer avian assemblages than conventional clearcutting. In this seminar, we draw comparison with the landscape configuration of old forest in eastern North America and parts of eastern Asia where fire is a less significant factor for landscape configuration of old forest.