Amur honeysuckle (Lonicera maackii) is an invasive species that has been shown to have detrimental effects on many terrestrial systems. However, little research has been done on how cross boundary subsidies such as leaves and woody debris are impacted by dense and often overarching Amur honeysuckle invasion in headwater stream riparian zones. Therefore, the aim of this study is to understand the influence of a gradient of Amur honeysuckle, located in the stream riparian zone, on the contribution of organic subsidies to stream systems in Southwestern Ohio. Leaf litter collection baskets were established in the riparian zone of five headwater, 30 meter reach, streams along a gradient of Amur honeysuckle. Additionally, coarse woody debris (>10cm diameter) and fine woody debris (0.5- 9.9 cm diameter) was measured in the terrestrial and aquatic habitats using the Van Wagner line intersect method and the three-dimensional formula of Ellis. This data was then used to determine leaf litter and woody debris biomass, so differences in organic subsidy contribution could be examined along the gradient.
Results/Conclusions
As a whole, the analysis of the non-honeysuckle leaf species litter biomass along the gradient proved to have no apparent differences from the reference sites to the heavily invaded site (statistical analysis pending). Data and statistical analysis is ongoing for the terrestrial and aquatic coarse and fine woody debris. However, we anticipate similar results to the leaf litter analysis. We believe the result of no impact of Amur honeysuckle in the riparian zone on leaf litter subsidies to be a result of the fact that the impact of the Amur honeysuckle invasion was not strong enough to overcome the impact of the riparian zone heterogeneity and spatial differences, which appear to be a strong driving force in cross subsidy contribution. Despite the lack of a strong impact from Amur honeysuckle on overall leaf litter biomass contribution to streams, the presence of this invasive and its ability to take over riparian habitat still has negative consequences, especially due to the fast decomposition rate of Amur honeysuckle in relation to many native species.