Cross-habitat and cross-kingdom biodiversity effects: Riparian forest invasion by Lonicera maackii regulates aquatic macroinvertebrate and microbial communities

Background/Question/Methods

Invasion of headwater stream riparian zones by exotic shrubs is an outstanding model system for understanding cross-systems subsides between terrestrial and aquatic ecosystems.  Lonicera maackii is a highly successful invader of riparian forests along headwater streams in Midwestern North America and we are executing a series of studies to develop a mechanistic framework for understanding the functional connectivity between riparian and aquatic ecosystems

Results/Conclusions

In a riparian restoration experiment we have found (1) that the overarching canopy caused by L. maackii invasion of riparian zones acts as a “filter” for woody debris and native foliage, reducing the total organic matter input to the stream.  In an in-stream leaf breakdown experiment, our data indicate that (2) L. maackii has litter that decomposes significantly faster than native species.  In fact, we recorded in-stream breakdown rates of L. maackii was 4 × faster than that of native species.  The aquatic biota colonizing L. maackii leaf packs was different than native leaf packs in terms of total density, taxonomic composition, and functional feeding group dominance.  We also have data that suggest (3) biofilm formation on L. maackii foliage is more rapid, with more structurally complex architecture, and with altered taxonomic composition. Taken together, our data suggest that riparian biodiversity loss and community simplification in headwater stream riparian forests, caused by a terrestrial exotic plant, has cascading effects on aquatic microbial and macroinvertebrate communities, trophic structure and cross-system energy/nutrient flow.  We are particularly interested in the idea of mirroring biodiversity effects, where the loss of biodiversity in the terrestrial habitat simplifies the aquatic habitat template which results in biodiversity loss in the macroinvertebrate and microbial communities.  Ongoing work will pursue these lines of inquiry.