This study consisted of two research projects in the Wyoming big sagebrush
(Artemisia tridentata ssp. wyomingensis (Beetle & A. Young) S.L. Welsh) alliance,
the most extensive of the big sagebrush complex in the Intermountain West. In the
first project, we intensively sampled 107 relatively undisturbed, late seral Wyoming
big sagebrush sites across the High Desert, Humboldt, and western Snake River
Ecological Provinces to investigate vegetation heterogeneity and the relationship of
environmental factors with vegetation characteristics. Vegetation characteristics were
highly variable across the region. Perennial grass and total herbaceous cover varied
more than six and sevenfold, respectively between minimum and maximum values.
Sagebrush cover averaged 12%, but ranged between 3 and 25%. With the exception
of perennial grass cover (p<0.0001, r²=0.52), limited variability in other vegetation
characteristics was explained by environmental variables.
In the second project, we investigated the functional role of Wyoming big
sagebrush by using undisturbed and sagebrush removed (with burning) treatments and
comparing vegetation and microsite characteristics under (subcanopy) to between
sagebrush canopy (interspace) zones. Wyoming big sagebrush influenced associated
vegetation and microsites. On sites receiving high incidental radiation, perennial grass
and total herbaceous cover and density were greater in the subcanopy than interspace
zones (p<0.05). On north aspects, these differences were not as pronounced
suggesting sagebrush's influence on associated vegetation is site dependent.
Temperature extremes were mediated and soil water content was greater in the
subcanopy than interspace zones during the growing season. Results indicated that the
subcanopy zone can be a more favorable environment to herbaceous vegetation than
the interspace zone. Wyoming big sagebrush is important to community resource
capture and use. Plots with sagebrush had greater soil water content at the start of the
growing season and produced more total biomass compared to where sagebrush had
been removed in both post-fire years (p<0.05). However, higher Thurber's
needlegrass photosynthetic rates and greater herbaceous cover and production where
sagebrush had been removed suggested that more resources were available to
herbaceous vegetation in the absence of sagebrush. / Graduation date: 2006
| Identifer | oai:union.ndltd.org:ORGSU/oai:ir.library.oregonstate.edu:1957/29053 |
| Date | 19 September 2005 |
| Creators | Davies, Kirk W. |
| Contributors | Miller, Richard F., Bates, Jonathan D. |
| Source Sets | Oregon State University |
| Language | en_US |
| Detected Language | English |
| Type | Thesis/Dissertation |
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