Effects of white‐tailed deer exclusion on the plant community composition of an upland tallgrass prairie ecosystem

Abstract

Questions: Grasslands support ecosystem services, promote diversity, and assist in carbon sequestration. However, grasslands worldwide are diminishing in area, and understanding the drivers shaping the remaining grasslands is critical for their maintenance. The North American tallgrass prairie covers approximately 13% of its historical range and is shaped by fire and herbivory. Fire frequency negatively correlates with plant species richness, while bison (Bos bison)-the historical grazers-offset this effect. However, bison populations have declined, and large browsers are increasing in density. Few studies though have examined the role of large browsers-particularly white-tailed deer (Odocoileus virginianus)-and their interaction with fire frequency in tallgrass prairies. Here, we addressed two questions: (a) What are the impacts of deer on plant diversity, species identities, and relative abundances; and (b) is there an interactive effect between the pressures exerted by deer and the well-documented effects of fire in driving plant community responses? Location: This study took place at the Konza Prairie Biological Station in northeastern Kansas, USA. Methods: Using a 22-year deer exclosure experiment, we examined differences in plant species richness, evenness, and plant community composition between plots that were either accessible or inaccessible to deer, in areas burned annually or once every four years. Results: We did not find significant effects of deer or interactive effects between deer and burning frequency on any metric of the plant community measured, including plant species richness, evenness, and plant community composition. Conclusions: Contrary to the impact that deer have in other ecosystems (e.g. forests), our results indicate that deer do not affect the plant community of herbaceous-dominated tallgrass prairies. These results indicate that while the loss of bison-grazers has shifted tallgrass prairie plant communities to C 4 grass-dominated systems, the shift to browsing-dominated herbivore pressure from deer has a minimal effect on the plant community. 900 | Journal of Vegetation Science BLOODWORTH eT aL.

Trade-offs between deer herbivory and nitrogen competition alter grassland forb composition

“…Deer florivory might cause grassland communities to lose poorly defended forbs, whereas grazers such as B. bison consuming grasses might increase forb abundance. For example, our study reinforces a similar finding from the Konza Prairie that white-tailed deer have no detectable effect on dominant C4 grasses (Bloodworth et al 2020 ). However, by explicitly looking at different forb species, we found that they could have markedly different responses to deer.…”

“…In contrast to forbs, we found greater abundance of the C3 grass species P. oligosanthes in unfenced plots and no effect of fencing on the abundance of the native C4 grass S. nutans , consistent with deer being browsers with minimal impact on grasses with intercalary meristems and low-nutrient tissues (Gordon and Herbert 2019 ; Bloodworth et al 2020 ). We speculate that the greater biomass of P. oligosanthes outside the fence may be a response to deer trampling and/or increased light availability.…”

Effects of Gopher Tortoise (Gopherus polyphemus) Exclusion on Plant Assemblages in a Longleaf Pine Forest

“…While our 15% reduction in richness and 12% in plant diversity were about half the effect size found by Richardson & Stilling, we suspect that future studies will reveal that the effects of tortoise exclusion will increase with time. Significant impacts of herbivore exclusion experiments after one year of exclusion are rare in the literature, and significant effects build up after multiple years (Moorhead et al 2017, Shelton et al 2014, Frank, Rathfon and Saunders, 2018Schäfer et al, 2019;Bloodworth, Ritchie and Komatsu, 2020). In longleaf pine forests in southern Alabama, white-tailed deer exclusion had no effect on plant diversity and cover after four years of exclusion (Brockway and Lewis, 2003).…”