SummaryThe major ecological features of oldgrowth coniferous forests in the Douglas-fir region are reviewed. Special attention is given to characteristics that distinguish oldgrowth forests from managed and unmanaged (natural) young stands. The primary exemplary type is 350-to 750-year-old Douglas-fir-western hemlock forest typical of the western slopes of the Cascade Range, but other types and locales are discussed. Management techniques for maintenance of oldgrowth forests are also considered. Major conclusions are:1. Approximately 175 to 250 years are required to develop old-growth forests under natural conditions in both Coast and Cascade Ranges. Development of old growth is faster on good sites than on poor sites.2. Few plant or animal species are solely confined to old-growth forests, although many speciesincluding several vertebrates, saprophytic plants, and epiphytic lichens-find optimum habitats in such forests. Some organisms, however, may require old growth to maintain viable populations. Moreover, there are substantial differences in composition and relative abundance of species between young-and old-growth forests.3. Gross productivity is maintained at high levels in most old-growth stands, but mortality generally balances growth. Thus, the merchantable board-foot volume tends to remain constant for several centuries or gradually decreases because the amount of defect increases. Total organic matter keeps increasing because of accumulated masses of dead tree boles, mostly as down logs.4. Old-growth forests are highly retentive of nutrients; large amounts are incorporated into living and dead organic matter. Losses of limiting nutrients, such as nitrogen, are low.5. Nitrogen-fixing epiphytes are abundant in old-growth trees, and bacterial nitrogen fixation appears to be common in the large woody debris characteristic of old-growth forests.6. Small-to medium-size streams in old-growth forests depend mainly on forest litter for an energy base. These materials are invariably partially utilized before they are exported downstream.7. The structure of old-growth forest is more heterogenous than that of young forests; coefficients of variation in tree sizes are greater, and understory patchiness is much higher than in young-growth stands.6. Most of the distinctive features of old-growth forests can be related to four structural features: (1) large, live old-growth trees, (2) large snags, (3) large logs on land, and (4) large logs in streams. The structural features are related over time.9. A large, old-growth Douglas-fir is individualistic and commonly has an irregularly arranged, large, coarse branch system, and often, a long crown. It is ideal habitat for specialized vertebrates, such as the red tree vole, northern spotted owl, and northern flying squirrel, as well as nitrogen-fixing lichens.10. Large snags are valuable as habitat for a variety of vertebrates and invertebrates and as a future source of logs.11. Logs on the forest floor are important habitats for small mammals, including species that dispe...

Methods have been developed to yield total tree estimates of biomass for various components of a tree (trunk, axes, twigs, and needles) and its community of epiphytes (microorganisms, lichens, and bryophytes). Trees were sampled with the help of climbing techniques modified from mountain climbing. Two stages of sampling were involved. First, all units of the population were described so that their weights could be predicted. Second, several units were chosen with probability of selection dependent upon predicted weight and sampled in detail. Biomass estimates from the sampled units were expanded to tree totals with information gathered during the first sampling stage. Internal structure of the crown (tree components and epiphytes) is illustrated by maps of trunk and branch systems and by diagrams of horizontal and vertical distributions. This internal structure was also derived from the first sampling stage.These methods have been applied to nine old-growth Douglas fir trees (Pseudotsugamenziesii (Mirb.) Franco). Data from a single 400-year-old tree (1.46 m dbh, 77 m in height) in the H. J. Andrews Experimental Forest in the western Cascade Mountains of Oregon are presented. Biomass and surface area estimates are as follows: trunk, 26 870 kg, 223 m2; axes (>4 cm), 1530 kg, 81 m2; living twigs (<4 cm), 480 kg, 373 m2; dead twigs, 78 kg, 104 m2; needles, 198 kg, 2860 m2; lichens, 13.1 kg; and bryophytes, 4.7 kg. Total cell volume of microepiphytes on twigs was estimated to have been 300 cm3 and total cover by microepiphytes on needles was estimated to have been 191 m2.

JSTOR is a not-for-profit service that helps scholars, researchers, and students discover, use, and build upon a wide range of content in a trusted digital archive. We use information technology and tools to increase productivity and facilitate new forms of scholarship. For more information about JSTOR, please contact support@jstor.org.Abstract. Using direct-aid climbing techniques for sampling trunks and branch systems, we found 74 species of lichens and 32 species of bryophytes growing as epiphytes in a 450-year-old Douglas fir forest in western Oregon. Six epiphyte zones are described: base, moist side of trunk, dry side of trunk, upper trunk, axes of branch systems and branchlets of branch systems. The flora of each zone is compared with that of the rest of the tree and with that found on understory vegetation. We employed direct-aid mountain-climbing techniques to climb and sample living trees in a Douglas fir forest in western Oregon. Previous descriptions of Douglasfir epiphytes (Szczawinski, 1953; Coleman, Muenscher & Charles, 1956; Hoffman & Kazmierski, 1969) were based on samples from the lower trunk or felled trees. We relate epiphyte distribution to differences in bark and exposure of major subdivisions of the trunk and canopy. This paper is based on sampling designed to provide estimates of epiphyte biomass per hectare of forest to be used in ecosystem modeling undertaken by the Western Coniferous Biome, U.S. International Biological Program. Qualitative results only are presented here; our sampling methods are outlined to illustrate intensity of sampling. METHODS The study area consists of a series of small watersheds in the H. J. Andrews Experimental Forest 75 km east of Eugene, Oregon, in the Cascade Mountain Range. These watersheds ' This study began as a . We would also like to thank I. M. Brodo, J. W. Thomson, W. A. Weber and W. B. Schofield for their aid in identifying specimens.

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