Invasive plants usurp habitat space in the ranges they invade, creating a virtual monoculture in some instances. The impacts of invasion on community-level traits (e.g., species diversity) are relatively well understood, but less is known about impacts on ecosystem-level processes. We are approaching this knowledge gap using Lonicera maackii invasion in the Ohio Valley as a model system. In a series of studies, we compared ecosystem traits under and away from L. maackii. In a litter basket study we measured leaf litter input under and away from honeysuckle shrubs. In a separate study focused on throughfall we installed funnels under and away from L. maackii shrubs and compared the volume and chemistry of rainwater that passed through a native tree canopy (without the influence L. maackii) to that which passed through the canopy of L. maackii. We sampled three separate rainfall events across the growing season (May, August and November). In a third study, conducted in the same three sites, we used in situ incubations to assess nitrogen mineralization under and away from L. maackii shrubs.
Results/Conclusions
Data from the litter basket study indicated that leaf-fall phenology of L. maackii mirrors that of native species, contributing leaf material to the forest floor from early October through late November. Lonicera maackii differed from native species in also exhibiting a late-season, mid-December, pulse of leaves. Total leaf input from native species was similar under and away from shrubs; however, the deposited leaf mass of L. maackii was significantly (P < 0.001) higher under L. maackii shrubs. The throughfall study provided evidence that throughfall volume was lower under L. maackii than away during all samplings, and was significantly (P = 0.017) lower during the May sampling. In addition, rainwater passing through a L. maackii canopy had higher cation content than that which passed only through a canopy of native species. We did not find a discernable influence of L. maackii on net nitrogen mineralization in May, but did find strong evidence for a lower rate of nitrogen mineralization under L. maackii in August. In summary, we found evidence for L. maackii influence on a suite of ecosystem processes. Future work will seek to corroborate these findings and pursue understanding of the mechanism(s) of L. maackii influence.
