Site Characteristics as Predictors of Lonicera maackii in Second-Growth Forests of Central Kentucky, USA

Non-native invasive plants can negatively affect the abundance and survival of native plant species and alter ecosystem function. Amur honeysuckle (Lonicera maackii) is an invasive shrub that is an increasingly onerous problem for forest managers in eastern North America. We examined site-specific characteristics related to the presence and abundance of Amur honeysuckle, and other non-native invasive plants, in 15 second growth forests in central Kentucky. Individual remnants were characterized by: (1) frequency and cover of non-native invasive and native shrubs, (2) overstory tree basal area, (3) forest floor litter depth, (4) species composition of leaf litter, and (5) soil characteristics. Of the measured variables, the only statistically significant relationships we discovered were between Amur honeysuckle and characteristics of the forest floor. We found significant negative relationships between Amur honeysuckle presence and both forest floor litter depth (P = 0.01) and the percent of oak (Quercus spp.) litter on the forest floor (P = 0.004). The abundance (percent cover) of Amur honeysuckle was significantly and negatively related to forest floor litter depth (P = 0.03). These findings suggest that forest floor mass creates a barrier to invasion by exotic plants and that forests dominated by oak species may be more resistant to invasion by Amur honeysuckle. While this study did not identify a causal relationship between litter depth and oak litter and the presence of Amur honeysuckle, our findings do suggest that older forests, and those dominated by oak, may be more resistant to the invasion of Amur honeysuckle