Title: Vegetation of Oregon and Washington
Identifier: CAT92272720 (find matches)
Year: 1969 (1960s)
Authors: Franklin, Jerry F. cn; Dyrness, C. T
Subjects: Botany Oregon Ecology; Botany Washington (State) Ecology
Publisher: Portland, Or. : Pacific Northwest Forest and Range Experiment Station, U. S. Dept. of Agriculture
Contributing Library: U.S. Department of Agriculture, National Agricultural Library
Digitizing Sponsor: U.S. Department of Agriculture, National Agricultural Library

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Figure 63. — Pure, old-growth stands of Tsuga mer- tensiana are common throughout the Tsuga mertensiana Zone; note the clumping tendency of the trees in this stand near timberline (Gifford Pinchot National Forest, Washington). the zone (fig. 63), and Abies lasiocarpa or Pinus contorta, or both, in serai stands in drier portions of the zone. Abies amabilis is conspicuous in the zone in Washington and northern Oregon, but it drops out completely in the southern Oregon High Cascades. There are a wide variety of understory species of which many are Ericaceae, Rosaceae, and Compositae. The spectrum of communities found with- in the Tsuga mertensiana Zone varies locally with gradients in temperature, moisture, and accumulation and duration of snow, as well as geographically. In southern Washington the Tsuga mertensiana-Abies amabilis/Vaccinium membranaceum community is typical of modal sites. It has a depauperate understory composed of Vaccinium membranaceum, Xerophyllum tenax, Pyrola secunda, Rubus lasiococcus, and perhaps a few additional spe- cies. A variant of this community, in which the understory is completely dominated by a dense cover of Xerophyllum tenax, is com- mon in the southern Washington and northern Oregon Cascade Range (fig. 64). On wetter, cooler habitats, e.g., north slopes and along drainages, communities have dense shrub understories 1 to 1-1/2 meters in height. The most extreme example in south- ern Washington is a Chamaecyparis nootka- tensis/Rhododendron albiflorum/Gley Podzol association (Franklin 1966). A tangle of Vac- cinium ovalifolium, V. membranaceum, Rho- dodendron albiflorum, Menziesia ferruginea, and Sorbus spp. is characteristic of this shrub layer. Typical herbs include Rubus pedatus, R. lasiococcus, Valeriana sitchensis, Viola sempervirens, Listera caurina, and Erythroni- um montanum. In southern Oregon, the extensive Tsuga mertensiana communities found along the crest of the Cascade Range are much simpler structurally and floristically. The sparse un- derstories are usually dominated by Vaccini- um membranaceum or V. scoparium along with minor amounts of other species such as Chimaphila umbellata and Arctostaphylos nevadensis. Successional Patterns Large acreages of the Tsuga mertensiana Zone have been burned over during the last 150 years in southern Washington and Ore- gon. Consequently, serai communities are often conspicuous. Early stages in succession have not been studied, but they often involve domination of the site by fire-resistant species conspicuous in the understory — Vaccinium membranaceum and Xerophyllum tenax, for example. 76

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