Prepared by Kathryn J. Bloodworth, Mark E. Ritchie & Kimberly J. Komatsu
Grasslands make up approximately 40% of the Earth’s ice-free land surface, and they support diverse plant and animal communities that provide many ecological services. Therefore, the grassland ecosystem is crucial to understand and preserve. In the North American Great Plains, tallgrass prairies are particularly vulnerable, with only approximately 13% of the historical extent remaining due to land use change. These remaining tallgrass prairie fragments have further been altered by the near eradication of bison from the United States.
Historically, bison were the prominent large-bodied herbivore in the tallgrass prairie, and in combination bison and fire have shaped the structure of tallgrass prairie plant communities. However, the loss of bison from this ecosystem has resulted in white-tailed deer becoming the remaining natural large-bodied herbivore in the tallgrass prairie ecosystem.
The effects of deer on plant communities have been well studied in forest ecosystems, where deer often reduce the abundance of plant species they prefer to eat. However, the effects of deer in tallgrass prairie are less well understood. Because the feeding patterns of deer are much different from those of bison—with deer primarily browsing woody vegetation and large flowering plants and bison primarily consuming grass—we hypothesized that deer would have a different impact on the tallgrass prairie ecosystem than bison.
In this study, we utilized a 22-year old deer exclosure experiment in the Konza Prairie Biological Station in northeastern Kansas, USA, to ask two main questions: (1) What are the impacts of deer on the number and identities of tallgrass prairie plant species? and (2) Does the effect of deer herbivory vary across areas that are burned at different frequencies (yearly vs. once every four years).
We found that the removal of deer from this system did not impact the plant community and that this effect was consistent across areas burned yearly and once every four years. These results indicate that while the loss of bison has shifted the tallgrass prairie plant community, the new dominant large-bodied herbivore does not exert strong pressure on the plant community. We found that regardless of deer presence or fire frequency, C4 grasses dominate the tallgrass prairie ecosystem. Indeed, this dominance of C4 grasses—a food source that deer do not prefer—may be the reason why deer do not have a large impact on plant communities in this system.
Although we did not find strong effects of deer presence on the composition of tallgrass prairie plant communities, deer abundances are increasing both in this region and in many other ecosystems across the United States. Further research into the consequences of these increasing populations of the dominant remaining large-bodied herbivore may reveal interesting dynamics that have yet to be uncovered.
This is a plain language summary for the paper of Bloodworth et al. published in the Journal of Vegetation Science (https://doi.org/10.1111/jvs.12910).