Healthy Forests Require Combined Deer and Invasive Shrub Control

A recent WSSA research article shows significant drawbacks to focusing on just one threat to native forest regeneration

WESTMINSTER, Colo., April 1, 2025 /PRNewswire/ -- If left unchecked, both overabundant white-tailed deer populations and invasive shrubs like Amur honeysuckle (Lonicera maackii) can devastate deciduous native tree regeneration. Yet, a management strategy focused only on deer, or only on invasive shrubs, results in little or no forest health improvement, according to research from Ohio, spanning more than 10 years.

"Control of only invasive shrubs will reduce native cover and not improve tree regeneration," says David Gorchov, Ph.D., and Miami University (Ohio) biology professor. "Managing only deer will increase woody plants but reduce native cover. Management of both stressors is needed to promote tree regeneration and plant community restoration."

These conclusions summarize research, recently published online in Invasive Plant Science and Management (IPSM), volume 17, issue 1, by Cambridge University Press, a Weed Science Society of America (WSSA) research journal. For this study, Gorchov and his coauthors, M.S. student Marco Donoso and undergraduate honors student Hanna Leonard, investigated deer pressure and Amur honeysuckle effects for 11 years in a split-plot experiment in the Miami University Natural Areas in southwest Ohio, where both were at high density.

To conduct the research, Gorchov and another Miami University biology professor, Tom Crist, Ph.D., established deer exclosure and deer access plots in 2010, and removed invasive honeysuckle in each plot half. "Excluding deer, but not removing honeysuckle, significantly increased the density and species diversity of tree seedlings," says Gorchov. "However, for some tree species – Sugar Maple, Red Oak, Bitternut Hickory, Black Cherry, Redbud – the combination of deer exclosure and shrub removal was necessary to enhance abundance, though that same combination allowed some invasive plants, like Burning Bush and Winter Creeper, to thrive."

Forest regeneration failure means insufficient juvenile tree density to replace canopy trees. "We found that tree seedlings responded more to deer exclusion than to Amur honeysuckle removal but combining both measures results in the greatest tree seedling density and species richness," points out Gorchov. "Managing both deer and invasive shrubs is necessary to realize the greatest improvement in tree seedling density and diversity and recruitment of trees from seedlings to the understory-size class, as well as cover of native plants."

White-tailed deer and invasive shrubs that deer find palatable are commonly found in high densities in deciduous forests in the eastern and midwestern United States. As a result, these findings will help to inform forest managers throughout the region about successful practices to help forests thrive.

More information is available in the IPSM article, "Long-term interactive impacts of the invasive shrub Lonicera maackii and white-tailed deer (Odocoileus virginianus) on a deciduous forest understory." IPSM is the official publication of the Weed Science Society of America.

About Invasive Plant Science and Management
Invasive Plant Science and Management is a journal of the Weed Science Society of America, a nonprofit scientific society focused on weeds and their impact on the environment. The publication presents peer-reviewed original research related to all aspects of weed science, including the biology, ecology, physiology, management, and control of weeds. To learn more, visit www.wssa.net.

SOURCE Weed Science Society of America