FIGURE 18–2 Coarse woody debris, including standing dead trees and downed boles, are an important structural component of forests. An important goal in preserving ecological diversity is to maintain such structures within managed forest ecosystems. This rotting log is serving as habitat for a large variety of heterotrophic and autotrophic organisms. (Goar Marsh Research Natural Area, Giffort Pinchot National Forest, Washington.) Courtesy U.S. Forest Service.

Standing dead trees and fallen logs are essential to many organisms and biological processes within forest ecosystems (Harmon et al., 1986); yet, such structures have rarely been retained within managed forests. For example, Thomas (1979), in his compilation of the wildlife of northeastern Oregon forests, found that 178 vertebrates—14 amphibians and reptiles, 115 birds, and 49 mammals—used fallen logs as habitats. Elton (1966, p. 279) recognized the broad importance of dead wood structures for biotic diversity: “When one walks through the rather dull and tidy woodlands [of England] that result from modern forestry practices, it is difficult to believe that dying and dead wood provides one of the two or three greatest resources for animal species in a natural forest, and that if fallen timber and slightly decayed trees are removed the whole system is gravely impoverished of perhaps more than a fifth of its total fauna.” In addition to its role as a habitat for land animals, woody debris also provides habitats, structure, energy, and nutrients for aquatic ecosystems (Harmon et al., 1986). Furthermore, it provides sites for nitrogen fixation, sources of soil organic matter, and sites for the establishment of other higher plants, including tree seedlings (Harmon et al., 1986). Maintaining dead-wood structures should be a regular objective of silvicultural activities within the forests of the temperate zone and other zones, quite apart from any program for maintaining old-growth-forest conditions.

Maintaining nitrogen-fixing organisms within our forest landscapes is an example of maintaining functional diversity. Many nitrogen-fixing species of plants, such

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