Date of Award

Spring 1-1-2012

Document Type

Thesis

Degree Name

Master of Arts (MA)

Department

Ecology & Evolutionary Biology

First Advisor

Timothy R. Seastedt

Second Advisor

Sharon K. Collinge

Third Advisor

Carol A. Wessman

Abstract

Historically, prairie dogs (Cynomys spp.) have been considered essential to the health of western US grassland ecosystems by providing unique services and increasing vegetation community richness, evenness, and diversity. However, the persistence and return of black-tailed prairie dogs (Cynomys ludovicianus) to urban Boulder, Colorado may not result in the same ecosystem benefits historically associated with their presence. The urban landscape of Boulder presents prairie dogs with movement challenges unparalleled in natural landscapes, as well as suites of non-native plant species that have gained footholds in the region. This study examined the role of the prairie dog in urban Boulder to evaluate if the benefits to plant communities historically associated with their presence are maintained. The dataset for this analysis was comprised of 71 paired (occupied vs. unoccupied) vegetation surveys and 156 additional unpaired surveys collected from 1997 to 2010. Absolute cover of each species was determined for every survey resulting in a database of more than 280,000 individual observations. Mixed measure linear models were used to compare data from transects occupied and unoccupied by prairie dogs, as well as to evaluate the effect of prairie dog occupation duration. Results of this comprehensive analysis suggested that vegetation richness, evenness, and species diversity were all significantly lower (p < 0.01) in areas occupied by prairie dogs than unoccupied areas. Similarly, rates of vegetation and litter change, as well as the magnitude of bare soil exposure in Boulder are markedly different from those observed in the more natural landscapes of western South Dakota. This analysis of cover indicated that 12 species were significantly positively associated with the presence of prairie dogs, while 16 species significantly declined in their presence (p < 0.05 for all). Analysis of plant functional groups revealed the significant reduction of perennial native grasses (p < 0.01) as well as a significant increase in the cover of introduced forbs in occupied areas (p < 0.01). This study suggests that prairie dogs have a novel ecological role in Boulder, Colorado. Understanding how these changes to vegetation community compositions will affect ecosystem processes and services is necessary in order to develop informed management decisions that maximize the benefits of prairie dogs while minimizing the costs.

Appendix1.csv (12791 kB)
Appendix2.csv (2672 kB)

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