Assessing the effects of Amur honeysuckle control on native plant communities in southwest Ohio

Background/Question/Methods Amur honeysuckle (Lonicera maackii) is one of the most important invasive plants in the Ohio River Valley. Because of its phenology and dense canopy, it can exclude native herbs and interfere with regeneration of woody plants. I established modifed Whitttaker plots in four stands in a county park in southwest Ohio with a gradient of honeysuckle infestation intensities in 2005. Honeysuckle canopies were removed by herbicides in fall 2005. Plant cover was monitored every year from 2005 to 2007.

Results/Conclusions Species number and herb abundance increased after honeysuckle removal. Similarity indices for sites between 2005 and 2007 show the greatest change for sites with the most 2005 honeysuckle cover. This is supported by the species turnover and entry rates for each site. Overall flowering rates do not suggest any large response yet. It does appear that invasive species are entering all sites except for the site with minimal 2005 honeysuckle cover. Invasive species flowering has increased somewhat, although that trend is not completely clear. Tree seedling density is lower at sites with initially denser honeysuckle canopies, while honeysuckle seedling density appears to be higher. Overall, it appears that many responses to Amur honeysuckle removal are not initiated until the second growing season after removal. It also appears that sites with lighter honeysuckle canopies respond better to honeysuckle removal, in that fewer invasive species and more native woody plants are found at these sites 2 years after removal.