Competitive effects of native and exotic shrubs on Quercus alba seedlings

The exotic shrub Lonicera tatarica (Tartarian honeysuckle) has aggressively invaded woodlands and forests in central and eastern North America; however, its impacts on native plant species are not well understood. We used a greenhouse seedling experiment to examine the effects of L. tatarica on Quercus alba (white oak), the presettlement dominant tree of many of these forests. Growth-related parameters of Q. alba seedlings (height and basal diameter increases, biomass) did not differ between treatments when grown in monoculture or with L. tatarica competitors. In addition, when paired with native Cornus (dogwood) species, Q. alba displayed similar growth as when paired with L. tatarica. Quercus alba also did not respond differently to native and L. tatarica competitors across a range of densities, although greater competitor diversity resulted in somewhat lower height growth than other treatments. Due to the similarity in Q. alba growth across native and exotic shrub combinations, we argue that seedling-to-seedling competition with Q. alba is not a significant impact of L. tatarica invasion.