Date of Award:

5-2006

Document Type:

Dissertation

Degree Name:

Doctor of Philosophy (PhD)

Department:

Plants, Soils, and Climate

Committee Chair(s)

David W. Roberts

Committee

David W. Roberts

Committee

James N. Long

Committee

Leila M. Shultz

Committee

Thomas C. Edwards

Committee

Dale L. Bartos

Abstract

The distribution of vascular plant species and species richness in a mid-elevation Rocky Mountain landscape can be attributed to a number of variables. The distribution of species with respect to physiognomic type, patch size, shape, and environmental heterogeneity was assessed for a mosaic landscape comprised of conifer forest, deciduous forest, and shrub-steppe physiognomic types in the southwest comer of Grand Teton National Park, Wyoming. This vegetation is representative of that found in other montane landscapes of the central Rocky Mountains. The vegetation was mapped to physiognomic type; distinct vegetation patches were sampled using one or more small (50 m2) plots. This method allowed for sampling of very small as well as large vegetation patches. Species richness, distribution, and exotic species distribution were analyzed at the plot and patch level. A preference metric was developed and used to assess species preferences for each of the three physiognomic types.

Species preference for physiognomic type was analyzed for all species occurring at least 10 times in the 276-plot data set. Each of these species occurred in more than one physiognomic type. The majority of species showed a significant preference for a single physiognomic type, while several species had dual preferences. Species distributions were modeled using physiognomic type as a predictor variable as well as slope and aspect; type was a significant predictor variable in 70% of the individual species models.

Species richness was highest at both the plot and patch level in the shrub-steppe physiognomic type. Exotic species richness and proportion of exotic species present were also highest in the shrub-steppe vegetation. The deciduous forest vegetation is intermediate to the shrub-steppe and conifer vegetation in plot-level richness. Larger patches of deciduous forest had higher richness at both the plot and the patch level. Patch size did not impact plot level species richness in the other two vegetation types. The conifer physiognornic type had the lowest plot-level species richness, but high plot-to-plot variability (beta diversity). The species composition of the three physiognomic types is overlapping, but not nested - each contributes to the diversity of species found in this landscape.

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