Impacts of Cheatgrass (Bromus tectorum) on Western Fence Lizard (Sceloporus occidentalis) Populations in Nevada
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Authors
Bozanich, Kristina M.
Issue Date
2015
Type
Thesis
Language
en_US
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Abstract
The encroachment of cheatgrass (Bromus tectorum) has become a major crisis for
ecosystems in the western United States. Very little research has been conducted on the impacts
of cheatgrass on small vertebrates, including lizard species. This study was conducted to
evaluate whether cheatgrass impacts western fence lizard (Sceloporus occidentalis) populations,
and to explore possible causal mechanisms. Visual encounter surveys in this study displayed a
strong relationship of lizard encounters in sagebrush areas in contrast to cheatgrass-dominated
zones. Potential mechanisms reducing lizard populations in cheatgrass environments (or causing
emigration away from cheatgrass sites) are reductions in lizard mobility, altered micro-site
temperatures, and altered plant and insect diversity. Experiments on lizard mobility showed that
smaller lizards are significantly impacted by the physical resistance imposed by thick blankets of
cheatgrass, compared to larger lizards. Temperatures of cheatgrass areas have a larger
temperature range than sagebrush areas. For plant diversity, data were insufficient for analyses.
Cheatgrass areas were not found to support high insect diversity, in terms of insect richness
(number of species) and abundance (number of individuals). Sagebrush areas did not support
higher insect richness, but contained higher insect abundance. Overall, conclusions from this
study, among other supporting research, warns that cheatgrass negatively impacts lizard
populations and threaten other obligate species as well. Serious considerations should be taken
on how to prevent cheatgrass’ influences on lizard populations and the native habitat that the
populations depend on.
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In Copyright(All Rights Reserved)