. Vegetation of Oregon and Washington. Botany Oregon Ecology; Botany Washington (State) Ecology. From the 11 associations and variants de- scribed by Driscoll (1964a, 1964b), we can pick five which typify major variations in Ju- niperus occidentalis communities (table 19). The Juniperus/Artemisia/Agropyron associa- tion was found on well-drained loamy soils on undulating topography; hence, its climatic cli- max designation. Artemisia tridentata (aver- age maximum height m.) and Agropyron spicatum typified the shrub and herb compo- nents, both attaining maximum status here. Chrysothamnus na
. Vegetation of Oregon and Washington. Botany Oregon Ecology; Botany Washington (State) Ecology. From the 11 associations and variants de- scribed by Driscoll (1964a, 1964b), we can pick five which typify major variations in Ju- niperus occidentalis communities (table 19). The Juniperus/Artemisia/Agropyron associa- tion was found on well-drained loamy soils on undulating topography; hence, its climatic cli- max designation. Artemisia tridentata (aver- age maximum height m.) and Agropyron spicatum typified the shrub and herb compo- nents, both attaining maximum status here. Chrysothamnus nauseosus was the only other shrub. Stipa thurberiana, Poa secunda, Lo- matium triternatum, Bromus tectorum, and Festuca octoflora were other notable species. The Juniperus/Festuca association was no- table for its high coverage of Juniperus occi- dentalis and Festuca idahoensis and low shrub cover (table 19). The shrub cover was lowest in the Juniperus /Agropyron association. The Juniperus/'Artemisia-Purshia association was lowest in Juniperus occidentalis and highest in shrub coverage {Artemisia tridentata and Pur- shia tridentata). The Juniperus/Artemisia/A g- ropyron-Astragalus association (fig. 94) occu- pied the most xeric sites. Festuca idahoensis was found only in Juniperus shade in this as- sociation. Of the few perennial herbs, Astra- galus lectulus was quite specific to this associ- ation. Succession Very little is known concerning succession- al relationships in the Juniperus occidentalis Zone. Burning can kill Juniperus occidentalis and temporarily produce an herb- or shrub- dominated community which is gradually re- invaded by trees. Sparsity of Juniperus occi- dentalis in some associations was explained in this way (Driscoll 1964b). The fire-sensitive Pur shia tridentata is similarly affected. Graz- ing by cattle can result in a reduction of the preferred Agropyron spicatum and Festuca idahoensis; deer browsing affects primarily the Purshia tridentata and Juniperus
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