The Rain Forest Atlas - page 2
Page 2: The Rain Forests of Home, A Review of the Research
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A Review of Past and Current Research
Temperate rain forests have been recognized as a distinct biome throughout the 20th century, although ecologists have not used the term uniformly. Most vegetation classification schemes use vegetation structure (and, secondarily, unique fauna) to define biomes, but temperate rain forests can be structurally similar to nearby forest types. Temperate rain forests are also difficult to define floristically because they share species with warmer and drier forest types. Nevertheless, temperate rain forests have been included in most world vegetation maps and classifications (Koppen 1918, Kuchler 1949, Holderidge et al. 1971, de Laubenfels 1975, Udvardy 1975, Whittaker 1975, and Archibold 1995). (See Figure 2.) Several of these schemes, which define temperate rain forests primarily with climatic variables, are in close agreement.
Alaback's (1991) definition for temperate rain forests of North America is widely recognized and most useful for this analysis: over 1400 millimeters annual precipitation, cool summers stemming from an equable year-round climate, mean annual temperature between 4 and 12 degrees Celsius, and infrequent fire except in the redwood fogbelt. Kellogg (1992) used an approximation of this definition to create the first map of coastal temperate rain forest distribution.
Alaback (1991, 1995) has synthesized information to distinguish four zones of coastal temperate rain forest in North America. Other ecologists have mapped rain forest vegetation for parts of the region. These classifications, though fragmented by jurisdictional boundaries, reflect real taxonomic and environmental differences. Viereck et al. (1992) recognize a coastal forest type in Alaska. Pojar et al. (1991) propose that the coastal western hemlock zone defines the coastal temperate rain forest zone for British Columbia. In Oregon and Washington, Alaback's definition of coastal temperate rain forest includes all of Franklin and Dyrness's (1988) Sitka spruce zone and part of their western hemlock zone. For northern California, Barbour and Major (1977) recognize coastal redwood and mixed conifer-hardwood vegetation types in the area identified in this report as coastal temperate rain forest.
Mapping vegetation and the environmental status of the North American coastal temperate rain forest has been a patchwork affair. Morrison (1988) produced a seminal database of remaining old growth in the national forests of Washington, Oregon, and California, some of which contain significant areas of coastal temperate rain forest. Remaining old-growth vegetation has also been mapped for Vancouver Island, Haida Gwaii (the Queen Charlotte Islands), mainland British Columbia, and southeastern Alaska, with information on mid-century status included for comparison of the two Canadian islands (Sierra Club of British Columbia 1992, Broadhead 1995, Finch and Phipps 1993, MacKinnon and Eng 1995). Vegetation age and type have been mapped for Oregon's Coast Range using Landsat Thematic Mapper (TM) data as part of the Coastal Landscape Analysis and Modeling Study at Oregon State University. Ongoing research in that study aims to integrate social and economic information with forest cover and other environmental data (Spies, personal com-munication, 1995). Noss (1992) also focused on the Oregon Coast Range for a conservation plan that proposed reserves, corridors, buffers, and matrix areas based on rare species and habitats. Finally; the Forest Ecosystem Management Assessment Team (FEMAT) produced maps of vegetation and ecosystem status, and proposed options for management on federal lands in Washington, Oregon, and northern California.
National agencies have produced topographic maps that permit delineation of watersheds. State and provincial agencies and other organizations have used these maps for administrative purposes, especially for water and fisheries management (e.g. Oregon Trout's healthy salmonid stocks report [Huntington et al. 1994]). Individual initiatives have mapped vegetation and other environmental variables for single watersheds (e.g. Applegate, Lookout Creek, Carnation Creek, and the upper Willapa River). This report presents the first bioregional map of vegetation and ecosystem condition overlaid on a watershed template for the entire North American coastal temperate rain forest.
The Rain Forests of Home
The coastal temperate rain forests of North America occupy a place of central importance in the global future of this forest type. Originally covering some 25 million hectares, the narrow band of coastal forests between Alaska and northern California occupied slightly more land than all the other stands of coastal temperate rain forest combined. Topography and climate provide clues to their original distribution along the Pacific Coast of North America.
These rain forests have sustained human communities for at least five millennia, certainly longer than western red cedar has been dominant in coastal forests. Ecosystem and society developed simultaneously in the wake of the Ice Age: the forest and the sea shaped the coastal First Nations, and their resource use practices influenced the landscapes that European explorers would regard as "pristine." Perhaps nowhere else in the temperate zone were people and place more inextricably bound.
In many obvious ways, and probably in many more yet undiscovered, the thin band of coastal forest interlaced with ocean is utterly unlike the far more extensive interior forests that begin just a few hundred kilometers inland. It is more luxuriant: abundant rainfall and fog throughout the year, the absence of catastrophic fire, and a nearly snow-free climate promote rapid tree growth, while frequent fog sustains a heavy and diverse crop of mosses and lichens in the forest canopy.
These forests rarely burn, especially north of Vancouver Island. Large-scale fires are less frequent in coastal rain forests than in most other temperate forest types, and less probable than in other conifer forests. As a result, landscape-scale disturbances (other than industrial clearcuts and catastrophic blow-downs in young even-aged stands) seldom occur here, while more localized disturbances, including wind-throws and landslides, create a multitude of smaller openings in which young trees germinate and grow. The resulting forest stands include vigorous trees of all ages, as well as many dead and dying trees. This diversity of tree ages and sizes creates a wide variety of microhabitats for other plants and animals.
Intricate networks of streams, wetlands, and estuaries lace through coastal rain forest watersheds, creating habitats for freshwater and anadromous fish, for wildlife dependent on aquatic habitats, and for plants adapted to wet conditions. These riparian habitats create natural corridors for animal movement, and the streams that shape them distribute nutrients throughout the landscape. The unique plant and animal communities found both above and below ground in riparian zones contribute elements of biodiversity found only in coastal forests. The watersheds that surround these rivers and streams form important ecological units that integrate the distribution of fish and animals, the flows of energy and water, and the movement of materials.
North America's coastal rain forests contain more than 30 tree species and about 250 species of birds and mammals. The diversity in these groups, though not exceptional by global standards, includes species that better embody the interdependence of land and sea than perhaps any others. No living things demonstrate more dramatically the reciprocity of forest and sea than the seven species of Pacific salmon and trout that range widely in the North Pacific while they grow to maturity, then return to their natal coastal rain forest streams to spawn. Avian counterparts of the salmonids, the birds known as alcids (the murres, puffins, and their kin) have equally extraordinary life histories. The marbled murrelet spends its days at sea feeding on capelin, smelt, and small shellfish, returning to shore at nightfall to nest on moss platforms on the upper branches of old-growth trees. The common murres and other burrow-nesting alcids range the open ocean, only coming ashore to breed in sizable colonies at the forest's seaward edge or on offshore islands. Such creatures weave land and sea into a coherent whole — a whole recorded in the myths and teaching tales of Native peoples.