This study examined the effects of both an intense weather event and land-use variables on butterfly communities occurring on City of Boulder Open Space and Mountain Parks land. In the first part of the study, butterfly community measures were examined across six habitats in a year that experienced severe heat and in which precipitation was 35% below average, and then again five and six years later when temperatures were milder and precipitation levels higher. Community measures were compared and used to assess the how the severe weather event affected butterfly communities, whether they recovered from this event, and how these responses differed across habitats. The second part of this study examined whether butterfly communities were affected by both natural and anthropogenic land-use variables.
The year of the severe weather event was characterized by the lowest total butterfly abundance and species richness of any survey year, suggesting that communities were negatively impacted by the high heat and low precipitation. In addition, butterfly abundance and species richness varied by habitat type in response to the drought, with communities occurring in Montane Woodlands exhibiting the lowest abundance and species richness of any habitat type. This habitat may be particularly susceptible to the effects of adverse weather. Finally, total butterfly diversity was highest in the year of the severe weather, likely due to the low abundance and species richness. Butterfly diversity did not vary in response to habitat type. Overall, butterfly community measures improved in the years following the severe weather event, suggesting that six years is sufficient for the recovery of these communities in the Boulder area.
The responses of butterfly communities to natural and anthropogenic land-use variables fluctuated across survey years, and were influenced by the severe weather event. As proximity to streams decreased, communities consistently showed higher butterfly abundances and species richness, and this was most pronounced in the year of high heat and low precipitation. Livestock grazing also had a significant effect on butterfly communities in this study, with communities occurring on un-grazed tracts of land showing higher abundance and species richness in years that were not subject to severe weather. In the year of high heat and low precipitation, butterfly community measures did not differ in response to grazing. Finally, the proximity of roads and trails had little effect on butterfly communities in this study, though species richness did decrease significantly as distance to nearest road increased in the year of high heat and low precipitation.
|Advisor:||Bowers, M. Deane|
|Commitee:||Breed, Michael D., Linhart, Yan B.|
|School:||University of Colorado at Boulder|
|Department:||Ecology and Evolutionary Biology|
|School Location:||United States -- Colorado|
|Source:||MAI 47/05M, Masters Abstracts International|
|Subjects:||Ecology, Organismal biology|
|Keywords:||Butterflies, Community, Habitat, Land use, Precipitation, Temperature|
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