Biotic homogenization: A comparison of urban, suburban, and exurban vacant lot plant and soil communities

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Megan Herrmann and Emily S. J. Rauschert, Biological, Geological and Environmental Sciences, Cleveland State University, Cleveland, OH, Sarah R. Carrino-Kyker and David J. Burke, The Holden Arboretum, Kirtland, OH

Background/Question/Methods
Biotic homogenization is the global trend of increasing similarity between biotic communities in different locations resulting in a loss of regional distinctiveness. One potential driver of biotic homogenization is urbanization. Urban areas are thought to create similar environments world worldwide. These spaces are characterized by the urban heat island effect, patchy land uses, built environments, and are hotspots of disturbance and human activity. Understanding the ecology of vacant lots is critically important in shrinking cities, such as Cleveland, Ohio, where vacant properties are present in abundance and represent a large proportion of the available greenspaces. This study aims to investigate whether vacant lot plant and soil microbial communities are more homogenized with increasing intensity of urbanization. Sites were chosen across three levels of intensity of urbanization: urban (Cleveland), suburban (Lake County) and exurban (Holden Arboretum). Randomly placed one-meter quadrats were used to assess the presence and percent cover of plant species, and soil samples were taken to assess trends in the soil microbial community. Terminal restriction fragment length polymorphism (TRFLP) was used to examine the soil fungal diversity. Plant and soil community alpha and beta diversity analyses were performed to assess trends in community compositions between and within site types.
Results/Conclusions
The mean plant species richness differed between vacant lot sites (ANOVA, F2,9=7.4, p=0.013). A post hoc Tukey’s test showed that exurban sites had significantly higher mean species richness than urban sites (p=0.011); the suburban group was not significantly different from the other two groups. Preliminary analyses of the soil samples found a significant difference in community composition between site types (PERMANOVA, F2,133=7.6699, P<0.001). Furthermore, there were differences in species turnover between site types (ANOVA, F2,131=3.3096, P=0.0.03961). Urban sites had significantly lower beta diversity than exurban sites (Tukey’s HSD, P=0.0454582), while no significant differences were found between the suburban sites and either of the other two site types. This suggests that there is a relationship between urbanization and homogenization of the soil fungal community, and the results from the vegetation surveys suggest a relationship between urbanization and the diversity of vacant lot plant communities. Ongoing work further investigates the plant community composition changes with urbanization intensity. Improving our understanding of the ecological impacts of anthropogenic activities can help minimize our impacts on ecosystem functioning in the future.