The impact of bush honeysuckle (Lonicera maackii) removal on arthropod diversity in an urban forest

Background/Question/Methods

Invasive plant species can impact local ecosystems by out-competing and replacing native plant species. This plant community change may affect arthropod abundance and species composition, with possible implications for other trophic levels. Bush honeysuckle (Lonicera mackii) is an invasive species in the northeastern United States. It forms dense shrubs, eliminating other plant species in these stands due to resource competition and allelopathic effects. To determine the impact of bush honeysuckle on arthropod community structure and the possible effects on pollination services, ten 10 meter x 10 meter paired plots were established in heavily invaded areas of Cherokee and Seneca parks in Louisville, Kentucky. In January 2009, all L. mackii was removed from one plot in each pair. Arthropods were sampled in all plots using pitfall and sticky traps in April, July, and August of 2009, and in May, July, and November of 2011. Differences in abundances, species richness, and functional groups were determined between removal and invaded plots.

Results/Conclusions

Abundance and species richness of arthropods collected from pitfall traps were not significantly different between removal and invaded plots in any season. In summer, arthropod abundance and species richness determined from sticky traps were also not different between removal and invaded plots. However, arthropod abundance determined from sticky traps was 25% higher in invaded sites during spring, and 20% higher in removal sites in fall. Arthropod species richness determined from sticky traps was 15% greater in invaded sites in spring, and was 30% greater in removal sites in fall. There were no differences in pollinators between paired plots in any season. Seasonal differences in arthropod abundances and species richness were due to changing predator and herbivore numbers. Honeysuckle provides cover, forage, and floral resources that may have increased arthropod species richness and abundance in spring. In fall, arthropod numbers increased in removal plots, possibly due to the increased visibility of the sticky traps or because of more light penetration and warmer temperatures. Pollinator services appear unaffected by honeysuckle removal.