. Vegetation of Oregon and Washington. Botany Oregon Ecology; Botany Washington (State) Ecology. Forest development on burned areas is often very slow, as would be expected in the severe environment of this zone. In some cases, semipermanent communities of Vaccin- ium spp., Xerophyllum, Sorbus spp., and Spiraea have been created by repeated burn- ing (fig. 65). Indians used this method to per- petuate fields of Vaccinium membranaceum from which they collected berries for food. Successional sequences of tree species vary geographically. On moist sites, Tsuga merten- siana and Abies amabilis can
. Vegetation of Oregon and Washington. Botany Oregon Ecology; Botany Washington (State) Ecology. Forest development on burned areas is often very slow, as would be expected in the severe environment of this zone. In some cases, semipermanent communities of Vaccin- ium spp., Xerophyllum, Sorbus spp., and Spiraea have been created by repeated burn- ing (fig. 65). Indians used this method to per- petuate fields of Vaccinium membranaceum from which they collected berries for food. Successional sequences of tree species vary geographically. On moist sites, Tsuga merten- siana and Abies amabilis can function as pio- neer species. On dry sites, and particularly in Oregon's High Cascades province, serai forests of Pinus contorta or Abies lasiocarpa are often the first to develop (fig. 66). These are gradually replaced by Tsuga mertensiana and, except in southern Oregon, by Abies amabilis. In Washington and northern Oregon, Abies amabilis appears to be the major climax spe- cies in closed-forest portions of the Tsuga mertensiana Zone (Franklin 1966; Thorn- burgh 1969). Although nearly all old-growth stands do contain mature Tsuga mertensiana, reproduction is often nearly absent; a full range of Abies amabilis size classes is usually present. Tsuga mertensiana and Chamaecy- paris nootkatensis may be minor climax spe- cies on some habitats. In southern Oregon, more tolerant arborescent associates are ab- sent from Tsuga mertensiana stands and Tsuga is the climax species. Apparently, regenera- tion develops after the old-growth stands be- gin to break up, since significant Tsuga mer- tensiana regeneration is not common under closed-forest canopies. Southwestern Oregon Southwestern Oregon is an extremely in- teresting and complex region environmental- ly, floristically, and synecologically. Climate ranges from cool and moist in the coastal re- gions to hot and dry in the interior valleys, which are the driest locales west of the Cas- cade Range. The geology and, consequently, so
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