WESTERN SPRUCE BUDWORM HERBIVORY INFLUENCES STREAM MACROINVERTEBRATE STRUCTURE AND BIOMASS
Stream-riparian interactions are often mediated by leaf litter inputs. In the Pacific Northwest, herbivorous Western Spruce Budworm (WSB) outbreaks have increased in intensity and extent along riparian areas of managed Douglas-Fir forests. We predicted high rates of WSB herbivory in riparian areas would increase microbial production and food resources of macroinvertebrates through increased amounts and lability of leaf litter inputs as frass and intensified solar radiation from canopy damage. We used stable isotopic signatures of possible macroinvertebrate food sources (Frass, FBOM, CBOM, algae, and moss) to identify contribution towards growth. We also identified macroinvertebrates from quantitative samples for community structure and biomass. Preliminary data shows total frass-derived macroinvertebrate biomass was greater in low WSB stream (600 mg/m2) from more collectors compared to the high WSB stream (100 mg/m2). However, the percent of frass-derived biomass was greater in the high WSB stream (28%) than low WSB stream (9%). The results suggest WSB activity upstream may have contributed to the unexpected contribution of frass in the low WSB stream and frass appears to be an important food resource for consumers.
Deion Everhart (Primary Presenter/Author), University of Central Arkansas, email@example.com;