. Vegetation of Oregon and Washington. Botany Oregon Ecology; Botany Washington (State) Ecology. (no climax implication is intended in naming the first three zones): Interior Valley Zone (Pinus-Quercus- Pseudotsuga) Mixed-Evergreen Zone (Pseudotsuga/ sclerophyll) Mixed-Conifer Zone (Pseudotsuga- Pinus-Libocedrus-Abies) Abies concolor Zone Abies magnifica shastensis Zone The Abies magnifica shastensis Zone is bounded at its upper limits by the Tsuga mer- tensiana Zone (discussed earlier) wherever ele- vations are sufficiently great (Siskiyou Moun- tains and Cascade Range). The arrangement of th
. Vegetation of Oregon and Washington. Botany Oregon Ecology; Botany Washington (State) Ecology. (no climax implication is intended in naming the first three zones): Interior Valley Zone (Pinus-Quercus- Pseudotsuga) Mixed-Evergreen Zone (Pseudotsuga/ sclerophyll) Mixed-Conifer Zone (Pseudotsuga- Pinus-Libocedrus-Abies) Abies concolor Zone Abies magnifica shastensis Zone The Abies magnifica shastensis Zone is bounded at its upper limits by the Tsuga mer- tensiana Zone (discussed earlier) wherever ele- vations are sufficiently great (Siskiyou Moun- tains and Cascade Range). The arrangement of these zones in the Cas- cade Range and eastern and western Siskiyou Mountains is illustrated in figure 67. The only major difference is the replacement of the Mixed-Conifer Zone by a Mixed-Evergreen Zone in the western Siskiyou Mountains. It will be obvious that most of the major forma- tions found in southwestern Oregon are actu- ally the northern extensions of formations which are considered typical of the California Coast Ranges and Sierra Nevada. Fire has played an extremely important role in southwestern Oregon. Fire danger can reach very high levels during the long, hot, dry summers. Fires, both naturally caused and Indian-set, were common prior to the arrival of the white man. Early settlers were responsi- ble for additional burning, but formal fire control activities have been in effect since the early 1900's. As will be seen, many of the communities are created and perpetuated by fires; , some sclerophyllous shrub (chapar- ral) types and Pinus attenuata forests. Fire and fire control activities are having a pro- found influence on the shape of the future ROGUE RIVER VALLEY East West Figure 67. — Arrangement of vegetation zones in the Cascade Range and western Siskiyou Mountains of south- western Oregon. 79. Please note that these images are extracted from scanned page images that may have been digitally enhanced for readability - coloration and appearan
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