. Vegetation of Oregon and Washington. Botany Oregon Ecology; Botany Washington (State) Ecology. study of changes in composition, productiv- ity, and soil erosion associated with grazing of these types in the Wallowa Mountains. Re- cently, Strickler (1961) continued this study and made interesting photographic and ana- lytic comparisons of conditions in 1938 and 19 56-57. Festuca viridula, Agropyron sub- secundum, Melica bulbosa, Stipa lettermanii, S. columbiana and Lupinus leucophyllus composed the virgin communities; total plant coverage was high. "Mixed grass-and-weed" and "w
. Vegetation of Oregon and Washington. Botany Oregon Ecology; Botany Washington (State) Ecology. study of changes in composition, productiv- ity, and soil erosion associated with grazing of these types in the Wallowa Mountains. Re- cently, Strickler (1961) continued this study and made interesting photographic and ana- lytic comparisons of conditions in 1938 and 19 56-57. Festuca viridula, Agropyron sub- secundum, Melica bulbosa, Stipa lettermanii, S. columbiana and Lupinus leucophyllus composed the virgin communities; total plant coverage was high. "Mixed grass-and-weed" and "weed-needlegrass" {Stipa spp.) commu- nities with a high proportion of bare soil char- acterized the overgrazed sites. Eriogonum spp., Gilia nuttallii, Penstemon rydbergii, Arenaria formosa, Artemisia tridentata, and Stipa spp. were generally higher in these communities. Eventual return of these communities to their climax state (dominance of Festuca viridula) appears questionable. Festuca-dominated meadows are often found on xeric subalpine habitats in the Olympic Mountains (Kuramoto 1968) and in the wetter parts of the Cascade Range. They are especially common in the rain shad- ows on the east and northeast slopes of the major volcanoes. Festuca viridula-Lupinus lat- ifolius meadows dominate the Sunrise Ridge area on Mount Rainier, for example (fig. 146); a pumiceous soil may be partially re- sponsible for extensive de- velopment there. The total community com- position on these sites is somewhat altered from that on inland sites, but the overall physiognomy and dominant genera are the same. Dynamics in the Timberline Vegetation Timberline areas are tension zones, dynam- ic ecotones, between tree and treeless regions. As at lower elevations, directional changes are constantly taking place in response to allo- genic (, long- and short-term climatic changes) and autogenic (changes in environ- ment brought about by organisms) factors. Successional consid
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