The purpose of this study was to document vegetation on "The Island", a
Research Natural Area at the confluence of the Crooked River and the Deschutes River in
central Oregon's Juniperus occidentalis Zone and to compare the results with an earlier
study reported in 1964 from 1960-'61 data. Present-day comparisons were also made
between "The Island" vegetation and three nearby sites. Percent cover and constancy of
major tree, shrub, grass, and forb species were considered along with percent cover of
litter, moss/lichen, rock and bare ground. Climatic data from the Metolius, OR Station
were examined, and the literature of succession especially succession in the juniper and
sagebrush steppe of the Great Basin was reviewed.
Data from 1992-'93 show more woody vegetation on "The Island", both tree and
shrub, than was measured thirty years ago. The only tree species present is Juniperus
occidentalis, while major shrub species are Artemisia tridentata and Purshia tridentata.
Grass cover appeared to be less, with a more even mix of the native perennial bunchgrass
species Agropyron spicatum, Festuca idahoensis, Poa sandbergii, and Stipa thurberiana,
than in the past when Agropyron spicatum and the alien annual grass, Bromus tectorum
dominated. The two plant associations identified in the 1964 report by Driscoll,
Juniperus occidentalis / Artemisia tridentata / Agropyron spicatum and Juniperus
occidentalis / Purshia tridentata / Agropyron spicatum were still identifiable, but the
shrub, Artemisia tridentata appeared to be entering areas where Purshia tridentata had
dominated in the past study. The present-day comparison sites showed many similarities
with sites on "The Island." The comparison sites in the Juniperus occidentalis / Artemisia
tridentata / Agropyron spicatum association measured slightly more tree and shrub cover
but similar grass cover when compared to "The Island." The comparison site in the
Juniperus occidentalis / Purshia tridentata / Agropyron spicatum association had more
tree cover and more Purshia tridentata cover, but less shrub cover generally and more
grass cover than the same association on "The Island." Forbs represented less than one
percent cover on all study sites. The differences recorded in 1992-'93 from that of the
study thirty years ago may reflect successional processes at work and a lack of any major
natural fires in the system. / Graduation date: 1996
| Identifer | oai:union.ndltd.org:ORGSU/oai:ir.library.oregonstate.edu:1957/34888 |
| Date | 13 November 1995 |
| Creators | Fox, M. Anne, 1939- |
| Contributors | Eddleman, Lee E. |
| Source Sets | Oregon State University |
| Language | en_US |
| Detected Language | English |
| Type | Thesis/Dissertation |
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