Underplanting response to Amur honeysuckle invasion and white-tailed deer herbivory in mixed hardwood forests
Competition from invasive plants and herbivory from wildlife are major deterrents to the regeneration of native trees. The invasive shrub Amur honeysuckle (Lonicera maackii) and white-tailed deer (Odocoileus virginianus) have both been found to negatively impact native tree regeneration and diversity in the Midwest. While the effects of both Amur honeysuckle and white-tailed deer have been studied independently, less is known about their combined effects on vegetation communities. We examined the potential use of underplanting for forest restoration in areas of Indiana where both white-tailed deer and Amur honeysuckle are abundant. We evaluated development of one-year old planted northern red oak (Quercus rubra) and American chestnut (Castanea dentata) seedlings at five sites in Indiana following deer exclusion and Amur honeysuckle removal. Each seedling was assessed at the beginning and end of the growing season for survival, browse, and growth over the course of two years. We also evaluated foliar nitrogen concentration using combustion analysis and water stress of planted seedlings using pre-dawn moisture measurements.
We observed higher survival of northern red oak in comparison to American chestnut across treatments. Preliminary results show that the survival of both species significantly decreased with the presence of white-tailed deer and/or Amur honeysuckle. Plant moisture stress was significantly greater in areas with Amur honeysuckle than without and was greater in the presence of white-tailed deer for American chestnut. Browse was not significantly different in areas with or without Amur honeysuckle. There was no significant difference in foliar nitrogen concentration among treatments; however height growth was significantly greater in the absence of deer for both species and was greater in the absence of Amur honeysuckle for American chestnut. Our results indicate that the exclusion of white-tailed deer and the control of Amur honeysuckle may be necessary for successful establishment of underplantings in forest restoration efforts.