One objective of wilderness and parkland fire-ecology research is to describe the relationships between fire and unmanaged ecosystems, so that strategies can be determined that will provide a more nearly natural incidence of fire. More than 50 yr of efforts directed toward exclusion of wildland fires in the Northern Rocky Mountains (western Montana and northern Idaho) have resulted in a definite and observable impact on the forest ecosystems in this region. Fire-ecology investigations in Glacier National Park and the Selway-Bitterroot Wilderness have helped to reveal the nature of this impact and to provide a better understanding of the natural role of fire within these coniferous ecosystems. Such areas provide a unique opportunity to study and test approaches designed to perpetuate unmodified ecosystems. However, we still don't understand all of the long-term consequences of fire control in those forest communities that have evolved fire-dependent characteristics.

Alpine larch (Larix lyallii) grows in or near the timberline zone on high mountains of the inland northern portion of the Pacific Northwest. Unlike other subalpine conifers, which are evergreens, this deciduous larch displays an affinity for cold rocky sites and often grows in tree form higher up on north slopes than even krummholz (shrubby) forms of its associates. Overstory and understory vegetations in alpine larch communities were only indirectly correlated. Vaccinium scoparium, Luzula glabrata, and Phyllodoce empetriformis were the most common understory dominants. The distinctly snowy—cold—timberline nature of alpine larch habitats is emphasized by the presence of Cassiope mertensiana, Phyllodoce glanduliflora, and Abies lasiocarpa krummholz among the 11 most common understory species. Unlike the larch, which is generally restricted to the timberline zone, nearly all associated plants have broader distributions in the subalpine forest proper or above tree limit. Alpine larch is a climax species on a wide variety of sites too severe for the more shade tolerant evergreens to form unbroken stands because of shortness of growing season, rock terrain, avalanches, blizzards, or extreme dryness or bogginess. When alpine larch ascends into what would otherwise be a strictly alpine habitat (above the limits of other conifers), its stands apparently modify the surface environment since subalpine understory species are generally able to ascend with it. Rarely the undergrowth is dominated by tundra species. Alpine larch is superior in invading freshly glaciated sites. The positive correlation of alpine larch to acidic substrates poor in mineral ions is in contrast to the substrate relationship of many other timberline conifers, which are calciphiles.

No abstract

A gradient analysis and description was made of forest succession among the Thuja plicata—Tsuga heterophylla communities in the vicinity of Lake McDonald in Glacier National Park Montana. Thirty—three pioneer, seral, and climax communities located on well—drained slopes at elevations between 3,200 and 3,500 ft (1,050—1,150 m) were sampled. Through the calculation of indices of community similarity and dissimilarity, the stands were objectively arranged along a unidimensional gradient. The data summarized along the resulting ordination gradient provide a quantitative description of the basic successional pattern existing among these cedar—hemlock communities. Typically, following burning Pinus contorta communities become established, and these in turn are gradually replaced by Pinus monticola and Pseudotsuga menziesii in various proportions. Climax communities on the upland sites become dominated by Tsuga heterophylla, with smaller, but self—reproducing populations of Thuja plicata also persisting.

No abstract