PS 17-126
Effects of plague-extirpation on vegetation in prairie dog (Cynomys ludovicianus) colonies in Boulder, Colorado
Plague, caused by Yersinia pestis, is a significant disturbance that results in periodic epizootics on black-tailed prairie dog (Cynomys ludovicianus) colonies. Changes in vegetation on prairie dog colonies before and after plague in urban and suburban areas may exhibit unusual patterns because urban areas experience additional disturbances related to urbanization, climate warming, nitrogen deposition, and propagule pressure from exotic plant species. Urban prairie dog colonies differ significantly from rural colonies by having higher density of prairie dogs, higher richness and cover of exotic vegetation, and higher percentages of bare ground. In this study we evaluate if plague epizootics mitigate prairie dog effects on vegetation in urban and suburban Boulder, Colorado. We used a set of 30 never colonized control-sites paired with 30 colonies that had experienced plague in 2006. We compared vegetation on never colonized grassland to parts of the colonies that had been recolonized in 2007, recolonized in 2010, and never recolonized. We use a point intercept method to estimate plant cover and species.
Results/Conclusions
Total species richness was higher on colonies that had been abandoned by prairie dogs for seven years and sites that had never been colonized than on colonies that had been recolonized one and three years after the epizootic. Bare ground was higher on the sites with active prairie dogs than on sites without, suggesting that seven years is adequate recovery for plant cover. Non-native species richness was lower on actively colonized parts of the colony, but non-native species cover did not differ significantly among the treatments. The lower number of non-native species on actively colonized parts may be related to overall lower species richness. However non-native species made up a higher percentage of the total plant cover on actively colonized parts of colonies than on uncolonized and never colonized sites. In addition graminoid cover increased after an epizootic but quickly decreased with active prairie dog colonization. Native species richness did not differ among the treatments, but native plant cover was highest on the treatment that had never been colonized, whereas colonized areas had a low percent native cover. Plague decimates prairie dog populations and plant richness and cover increase after these plague events.