Influence ofLonicera maackiiInvasion on Leaf Litter Decomposition and Macroinvertebrate Communities in an Urban Stream

Abstract

Lonicera maackii (Amur honeysuckle) is an aggressive alien shrub that invades many habitat types in the eastern United States, including riparian zones. The effects of L. maackii have been well documented in terrestrial ecosystems and can range from alteration of plant and insect communities to changes in ecosystem processes; however, the effects on aquatic ecosystems are less well known. Research on other invasive species has shown that replacement of native trees with exotic species can have significant influences on decomposition rates in nearby streams. This study investigated the direct and indirect effects of L. maackii invasion and management (removal) on leaf litter decomposition in an urban stream by placing leaf litter packs of L. maackii and the native Acer saccharum (sugar maple) in stream segments invaded by or managed for L. maackii. We found that L. maackii litter decomposed two times faster than A. saccharum litter, and that A. saccharum leaf litter supported a higher abundance of macroinvertebrates than L. maackii. Functional feeding groups of macroinvertebrates were also affected by the invasive species; significantly more scrapers were associated with A. saccharum litter, and predators were positively associated with both A. saccharum and invaded sites. Indirect effects of L. maackii presence along streambanks on leaf decomposition and macroinvertebrate communities were negligible, possibly due to overriding effects of urbanization on the stream. These results have important implications for stream ecosystems that run through terrestrial areas invaded by L. maackii, as stream diversity and nutrient retention are strongly influenced by allochthonous inputs.