File:Vegetation of Oregon and Washington (1969) (20547730236).jpg

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 147. — Changes in the subalpine forest-meadow ecotones have typically been gradual; however, massive invasions of meadow areas by tree species have taken place in the last 50 years all over the Cas- cade and Olympic Mountains (Paradise Valley, Mount Rainier National Park). toward a modal mesic type. Such changes may be extremely slow, however. Generally, the heather (Phyllodoce-Cassiope) and Vac- cinium deliciosum communities are consid- ered the higher levels of meadow successional series. Changes in the forest-meadow ecotone have undoubtedly been of greatest interest. Gradual expansion of tree groups appears to have been taking place for many years be- tween the forest and scrub lines except where fires produced temporary setbacks (Swedberg 1961; Franklin and Mitchell 1967). In the last half century, however, massive invasion of meadow areas has taken place at many loca- tions in the Northwest (fig. 147) (Brink 1959; VanVechten 1960; Fonda 1967; Franklin 1966). These invasions are probably related to a short-term climatic fluctuation. Changes in the overall elevation of forest line or scrub line have not been reported in this region with one exception — on Mount St. Helens. Mount St. Helens is a relatively
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Figure 148. — Timberline is low (1,340 m.) but advancing on Mount St. Helens, a Cascade Range volcano of very recent origin (less than 2,000 years old). 172

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