Publication Date

2025

Document Type

Dissertation/Thesis

First Advisor

Jones, Holly P.

Degree Name

M.S. (Master of Science)

Legacy Department

Department of Biological Sciences

Abstract

The reintroduction of grazing disturbance has become an increasingly popular tool in grassland restoration to build and maintain diverse and functioning ecosystems, but our understanding of how grazers like bison (Bison bison) shape plant communities is limited by binary grazing treatments and unanswered calls for in-depth and mechanistic examinations of community function and structure. Little research has focused on how natural variations in bison grazing intensity impact the function and structure of restored tallgrass prairie; whereby functional diversity is purely defined by changes in trait expression according to plant responses to grazing, and examining both vegetation structure and ecosystem function provide new understanding of the consequences of selective grazing. This study examined how bison grazing intensity influences plant functional diversity exclusively via functional trait expression, the structure (height and density) of vegetation, and ecosystem function (decomposition) in tallgrass prairie restorations. Trait-expression focused functional diversity was not affected by grazing intensity, but idiosyncratic changes in trait expression did occur under grazing, causing changes in functional diversity and trait space for some species, and contributing to slight shifts in trait space for the whole community. Vegetation height and density decreased with increasing grazing intensity, where the vegetation structure under low and no grazing intensity was similar. Decomposition decreased with increasing grazing intensity, but the rate of decomposition under no grazing was similar to grazed treatments. The results of this study illustrate that grazing intensity has more of an impact on vegetation structure and ecosystem function than it does on functional diversity. These findings suggest that grazing does not pose a threat to functional stability at some sites, which is good news for managers concerned about functional diversity losses. The findings also indicate that grazing lawn formation can help facilitate heterogeneity in vegetation structure, but may impede optimal ecosystem functioning in terms of efficient decomposition. Grazing intensity can have a complex relationship with community dynamics, but this study has improved our understanding of the role grazing intensity plays in function and structure, and empowers managers to make informed decisions on how to effectively apply grazing relative to their conservation and restoration goals.

Extent

91 pages

Language

en

Publisher

Northern Illinois University

Rights Statement

In Copyright

Rights Statement 2

NIU theses are protected by copyright. They may be viewed from Huskie Commons for any purpose, but reproduction or distribution in any format is prohibited without the written permission of the authors.

Media Type

Text

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