STREAM-RIPARIAN TROPHIC LINKAGE RESPONSE TO A RIPARIAN INVADER
The invasive pest hemlock woolly adelgid (Adelges tsugae; HWA) is decimating the eastern hemlock Tsuga canadensis, a foundational tree species in many Appalachian riparian forests. Ecological trophic networks (i.e., food webs) functionally link streams and their adjacent riparian zones, and HWA has high potential to alter these linkages owing to documented changes in stream benthic macroinvertebrate communities. At 21 forested headwater streams in Virginia, West Virginia, and Ohio, we quantified cross-boundary trophic dynamics in response to HWA-driven hemlock decline. For example, in-stream basal resource biomass was 1.7 (periphyton) and 3.9 (hemlock detritus) times larger at the reference sites. Benthic and emergent insect community differences were explained in part by degree of hemlock decline. Although riparian spiders (Araneidae and Tetragnathidae) showed no shift in trophic position or reliance on aquatically-derived energy (i.e., energetic pathways originating from benthic algae), their del15N isotopic signatures did track those of potential aquatic emergent prey. Taken together, our results imply that large-scale hemlock decline due to HWA is associated with cross-ecosystem functional shifts in both resources and consumers, leading to altered stream-riparian food webs and thus ecosystem function.
S. Mažeika P. Sullivan (Co-Presenter/Co-Author), The Ohio State University, firstname.lastname@example.org;
David W.P. Manning (Co-Presenter/Co-Author), University of Georgia, email@example.com;
Kristen M. Diesburg (Primary Presenter/Author), The Ohio State University, firstname.lastname@example.org;