Assessment of the Negative Role Amur Honeysuckle has on Urban Forest Diversity

Lonicera maackii (Amur Honeysuckle), an invasive shrub species, has out-competed native species in urban riparian zones for decades due to its ability to receive more sunlight and it also secretes an allelochemical from its leaves that negatively impacts the ecosystems. Our research question is how does Lonicera maackii affect native plant species in the herbaceous understory? Five forest communities were sampled in Northwest Illinois. Sites were separated into four different categories with L. maackii only, Garlic Mustard (Alliaria petiolata) only, Neither invasive species, and sites where both occur. There were 12 sites for each of the four categories resulting in 48 total. Daubenmire 1 m2 plots were placed haphazardly throughout the site. Native relative cover, native Shannon\u27s H, native richness, non-native relative cover, non-native shannons, and non-native richness were assessed. There was a site effect for native relative cover, native Shannon’s H, native richness, non-native relative cover, and non-native richness. There was a treatment effect for native relative cover, non-native relative cover, non-native Shannon’s H, and non-native richness. There was a site by treatment interaction for native relative cover, non-native relative cover, non-native Shannon’s H, and non-native richness. The data show that when comparing the effect L. maackii had on total relative native cover, four out of five sites had lower total native relative cover when L. maackii was present. All five sites had lower non-native Shannon’s H when L. maackii was present. We conclude that L. maackii has a significant effect on native plant species in the herbaceous understory. The data correlates to the literature with L. maackii’s presence lowering the amount of native plant species cover. A possible explanation is that L. maackii dominates native species with its shading ability as suggested from other studies