Conservation in the Present Time

Preserving biodiversity in temperate regions requires the maintenance of all successional stages. Since early successional stages are typically well represented, a major concern is preserving or recreating old-growth forests. Such old-growth forests typically contrast sharply with early successional stages in composition, structure, and function.

Old-growth Forests

Research presently under way will provide a definitive list of old-growth-dependent species within these temperate conifer forests. This list may include several other birds, several mammals (bat species may be notable), and several amphibians (particularly salamanders). Such forests are also very rich in mosses, lichens, and liverworts, of which at least one species --- a lichen--- is strongly related to old-growth forests. That species, Lobaria oregana, is an important nitrogen-fixing foliose lichen that grows in the crowns of old-growth Douglas-fir trees. Research will almost certainly show that some of the rich invertebrate community is also old-growth-dependent; more than 1,000 species have been identified within a single old-growth stand, the upper bole and crown providing particularly rich habitat. The old-growth forests obviously have a high genetic content and are far from the biological deserts that some game biologists and foresters once suggested.

Mosses

Lichens

Liverworts

Functional differences between old-growth and younger forests are often qualitative rather than quantitative. That is, forests at all stages fix and cycle energy or carbon, regulate hydrologic flows, and conserve nutrients. Some stages carry out these activities more efficiently than others, however. Old-growth forests in the Douglas-fir region are particularly effective at regulating water flows and reducing nutrients losses. Nutrient losses from old-growth watersheds in the Pacific Northwest are, for example, extremely low (Franklin et al.,1981), although this is not always true in other regions. Old-growth forests may contrast with younger forests in their influence on some important hydrologic processes. Old-growth coniferous forests present a very large crown surface and occupy an extensive volume of space, because dominant trees are commonly taller than 75 meters. Such forests are particularly effective at gleaning moisture from clouds and fogs, which can substantially increase precipitation. These forests may also influence the amount and spatial distribution of snowfall thereby minimizing the potential for the damaging rain-on-snow floods that are characteristic of the Pacific Northwest. In addition, the old-growth Douglas-fir forests provide several important sites for nitrogen fixation (e.g., epiphytic lichens and rotting wood), which are more limited or absent in earlier stages of succession.