2020 ESA Annual Meeting (August 3 - 6)

COS 243 Abstract - Deer herbivory alters plant community dynamics in the Edwards Plateau

Jeremy Collings, Department of Biology, University of Oregon, Eugene, OR and Thomas L. Arsuffi, Llano River Field Station, Texas Tech University, Junction, TX
Background/Question/Methods

Deer populations in the United States have been increasing since the beginning of the twentieth century. For much of the past century, ecologists have been conducting empirical research on the impacts of deer overabundance on ecosystems. Experimental research studies using deer exclosures have demonstrated that deer can modify multiple characteristics of plant communities. However, this research has been conducted in the Midwestern and Northeastern regions of the United States. Little research has been conducted on how deer impact plant communities in the state of Texas. Furthermore, research on deer impacts has historically been biased toward aboveground components of plant communities. Recent research has suggested that deer impact essential belowground processes such as associations between mycorrhizal fungi and plant roots. The goal of this study was to assess the impacts of deer on both above and belowground components of plant communities in the Edwards Plateau ecoregion of Texas. To do this, I conducted vegetation surveys, sampled standing crop biomass, and assessed mycorrhizal colonization rates in deer exclosures and paired open plots. I hypothesized that deer herbivory would decrease plant diversity, aboveground biomass, and mycorrhizal colonization. I also hypothesized that deer would have lifeform specific impacts on the plant community.

Results/Conclusions

From the vegetation data, I found that plant diversity was greater in exclosures than in open plots. I also found that the plant community composition differed between exclosures and open plots. I found no difference in standing crop biomass or mycorrhizal colonization rate. The findings of this study suggest that deer are impacting plant communities at a substantial rate. This study is based on one year of deer exclosure, and other studies have found that deer impacts on plant communities become more apparent as the time since exclosure increases. Thus, it is likely that differences between exclosures and open plots in these sites will continue to increase in coming years. It is also possible that changes in primary productivity or belowground interactions may require more time to respond to exclusion of deer. The results of this study serve as the first empirical support for community level impacts of deer in the Edwards Plateau ecoregion. Data was collected in an especially wet growing season, so further data collection should occur. Long-term research will be important in further investigating the intensity of these impacts as well as detecting indirect impacts of deer such as changes in belowground interactions due to aboveground herbivory.