Soil chemistry, not short-term deer exclusion, explains understory plant occupancy in Pennsylvania oak forests

A study of deer browsing has uncovered the contribution of soil chemistry to ‘the ghost of herbivory past’.

The loss of understory plant community structure and diversity has been attributed to decades of overbrowsing by white-tailed deer (Odocoileus virginanus). Deer exclusion experiments have supported this theory, yet, even in the absence of deer some species are failing to recover. Research shows that the recovery of browse-sensitive species, specifically lilaceous forest herbs and tree seedlings, is often slow or inadequate in areas dominated by browse-resistant vegetation even after deer densities are reduced. It is unclear why recovery of browse-sensitive species has been limited, but it is possible that browsing pressure is still too high or that vegetation dynamics have changed resulting in a competitive advantage for species that are browse-resistant. This lack of recovery has been termed a legacy effect of deer browsing and has been referred to as ‘the ghost of herbivory past’. It is possible however that other factors may be influencing the recovery of these plants. Changes to soil chemistry are a probable candidate yet little is known about the response of herbaceous plants, let alone whole plant communities, to changes in soil chemistry.

A. Kelly holds a mineral soil sample ready for bagging from a sampling site in Rothrock State Forest. Image credit: M. Antonishak.

In a recent study published in AoBPBegley-Miller et al. investigate the viability of soil chemistry as an alternative explanation for a lack of vegetation recovery in oak-hickory forests of Pennsylvania. The authors demonstrate the importance of soil chemistry conditions (i.e. macronutrients and potentially toxic metals) in determining the presence of specific plant taxa in these ecosystems. These findings suggest soil as an alternative, or additional, explanation for deer vegetation legacy effects. They also highlight how the use of phyto-indicators of deer browsing may be problematic when those species are also limited by unfavourable soil conditions. The authors suggest that future studies should focus on more long term monitoring to better demonstrate the importance of both browsing and soil chemistry on plant community composition.

Researcher highlight

Image credit: teatown.org

Danielle Begley-Miller grew up in southwestern Ohio, USA, where she attended Miami University until her graduation in 2011. From there, she pursued a MS graduate degree in biology at Wright State University working with Dr. Thomas Rooney. Her master’s work on the effects of white-tailed deer browsing on phylogenetic diversity lead to her first publication in AoB Plants, which was named editor’s choice in 2014. She continued her graduate work with Dr. Duane Diefenbach at Penn State University, earning a PhD in Wildlife and Fisheries Science in 2018. Since graduating, she has served as the Director of Science and Stewardship at Teatown Lake Reservation, a non-profit nature preserve and environmental education center in southeastern New York, USA.

Danielle is a plant community ecologist, focused on ecological interactions and their land management implications. She spent her entire academic career studying the impacts of white-tailed deer browsing in both agricultural and forested environments, and her work has helped inform deer management decisions for two state agencies. In her current role, Danielle regularly mentors both high school and college student research projects, offers outreach and education programs, and manages the land management priorities for a 1,000 acre nature preserve.

To find out more about Teatown Lake Reservation and the work Danielle does there please visit their website at teatown.org.