Date of Award

8-2024

Access Control

Open Access

Degree Name

Great Lakes Ecosystem Science

Department

Great Lakes Center

Advisor

Dr. Robert Warren II

First Reader

Dr. Robert Warren II

Second Reader

Dr. Daniel Potts

Third Reader

Dr. Christopher Pennuto

Abstract

European buckthorn (Rhamnus cathartica) is a non-native woody plant in North America that often grows in dense, monotypic stands, frequently displacing native plants and reducing species richness of invaded native communities. Given that plants are basal in most food webs, the homogenization of plant communities might be expected to cascade into homogenization at higher trophic levels (Hunter and Price, 1992). I investigated the multi-trophic effects of buckthorn removal at three levels: (1) ‘native,’ in which there were no buckthorn trees or shrubs, (2) ‘buckthorn trees,’ in which buckthorn was not removed and grew into spaced mature trees, and (3) ‘buckthorn shrubs,’ in which buckthorn was removed ten years prior, but grew back as dense, monotypic thickets. I measured plant species richness, pollinator richness and abundance, leaf litter invertebrate richness and abundance, and rodent abundance in each habitat type. Native plots had more than twice the plant taxonomic richness as the buckthorn tree or buckthorn shrub plots. Similarly, the abundance and richness of invertebrate pollinators in the native plots was twice that of the other habitats. The abundance and richness of bees (Apiform) did not differ between the native and buckthorn tree habitats, but Apiforms were almost nonexistent in the buckthorn shrub plots. Leaf litter invertebrate richness did not differ between habitats, but abundance was highest in native plots. The rodent community was dominated by white-footed/deer mice (Peromyscus), and they overwhelmingly were found in the buckthorn shrub plots. Overall, I found that the removal of invasive buckthorn cover increased native abundance and species richness at multiple trophic levels. These results suggest that homogeneity in primary producers cascades into homogeneity in adjacent and non-adjacent trophic levels – starting in both the green (native plants) and brown (leaf litter) food webs – resulting in reduced richness and biomass across the community.

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