Plant communities are greatly affected by disturbances such as fire and herbivory. Fire frequency in tallgrass prairies negatively correlates with plant species richness, resulting C4 grass dominated systems. There is also abundant evidence showing that bison reduce C4 grass dominance and increase plant diversity. However, there is little documentation of the effects of white-tailed deer herbivory in the North American Great Plains. Due to their eating habits, deer most likely decrease diversity and abundance of forbs and woody species in tallgrass prairies. We hypothesize that deer herbivory will increase C4 grass dominance while decreasing plant diversity and the interaction of deer herbivory and fire regime will have a super-additive effect at the Konza Prairie Biological Station. To determine the effect of deer herbivory and burn regime on the tallgrass prairie plant community structure, we assessed the response of several community metrics in three watersheds with different burn regimes where deer exclosure fences were established 22 years ago. Plant species identification was recorded both inside and outside of the 30 x 30 m deer exclosure fences in all three watersheds. Percent cover of all species within six 1 m2 plots in each deer removal treatment type and watershed was also recorded.
Results/Conclusions
A PERMANOVA using Bray-Curtis dissimilarity metrics showed that the plant species composition of the watersheds burned every 4 years was significantly different than that of the watershed burned annually; however, there was no significant difference between areas with and without deer herbivory. Additionally, a PERMDISP based on Bray-Curtis dissimilarities showed no significant difference in the dispersion of replicate plant communities by watershed or treatment type. Across plots, the watershed burned annually had significantly lower plant species richness than those burned every 4 years. However, at both the research area and plot levels, species richness did not significantly differ between deer removal treatment types. Similarly, there was a significant effect of watershed on plot level plant evenness and there was no significant effect of deer removal treatment. Rank abundance curves showed that Andropogon gerardii, a dominant C4 grass, was the most abundant in all six plots. Unexpectedly, our results showed that in the herbaceous-dominated uplands of Konza Prairie, deer herbivory is not affecting the plant community structure. Consequently more research across the North American Great Plains is needed to fully understand the effects of white-tailed deer herbivory in grassland dominated systems.