Investigation into the competitive mechanisms of the invasive shrub Amur Honeysuckle, Lonicera maackii

Background/Question/Methods

Lonicera maackii (Amur Honeysuckle) is an invasive, woody shrub that is well established in deciduous forests in southwestern Ohio and Kentucky. The deleterious effects of this shrub on native herbaceous plants and tree seedlings has been well documented, however, the mechanisms of competition are not fully understood. Through an examination of both above- and below-ground competition, we aim to better understand the mechanisms enabling L. maackii to successfully out-compete native flora and dominate forest systems. We studied multiple biotic and abiotic variables at fifteen L. maackii sites and fifteen non-invaded sites in a deciduous forest near Dayton, OH (USA). These variables include measures of percent leaf and plant cover, light intensity, soil moisture, organic and inorganic matter, and mycorrhizal colonization. 

Results/Conclusions

Our preliminary results support published accounts of reduced tree seedlings and herbaceous cover under L. maackii shrubs. No tree seedlings were found under many of the honeysuckle shrubs assessed, indicating the potential of direct habitat change due to the invasive species. Light intensity was lower under the shrubs than in control sites; however, canopy cover between sites was similar. The biomass of leaf litter under these shrubs compared to non-invaded sites was significantly lower. However, L. maackii sites had greater soil moisture levels and organic matter than did non-invaded sites. Preliminary mycorrhizal analysis indicates low levels of VA colonization of L. maackii shrubs. Arbuscules have yet to be identified in honeysuckle roots, thus leaving questions about the functionality of the association. By better understanding the mechanisms that enables L. maackii to out-compete native flora, restoration efforts can be enhanced to increase the biodiversity of forests degraded by invasive woody species.