. Vegetation of Oregon and Washington. Botany Oregon Ecology; Botany Washington (State) Ecology. o?0. 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 ser
. Vegetation of Oregon and Washington. Botany Oregon Ecology; Botany Washington (State) Ecology. o?0. 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. Please note that these images are extracted from scanned page images that may have been digitally enhanced for readability - coloration and appearance of these illustrations may not perfectly resemble the original Franklin, Jerry F. cn; Dyrness, C. T. Portland, Or. : Pacific Northwest Forest and Range Experiment Station, U. S. Dept. of Agriculture
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