WESTERN SPRUCE BUDWORMS STIMULATE COMMUNITY RESPIRATION VIA ORGANIC CARBON INPUTS
Western spruce budworms (Choristoneura occidentalis) are a native lepidopteran that has sustained epidemic levels in the past decade across western North America. Larvae consume new, nutrient-rich conifer growth each spring, and deposit frass, damaged conifer litter, and larval and adult cadavers to the forest floor and streams. These organic inputs could stimulate stream biofilm activity. We compared how cellulose, lignin, and leachates of frass or litter affected biofilm community respiration using nutrient diffusing substrata in eight streams before and during peak budworm activity. We found that litter and frass had higher nutrient response ratios (NRR) than cellulose and lignin (p<0.01). There was no difference between cellulose and lignin, although litter had higher NRR than frass (p=0.0056). NRR did not differ before or during peak budworm activity. Budworm frass deposition peaks in early summer during baseflow whereas litterfall peaks in winter during high stream flows (p<<0.001). Therefore, budworm herbivory shifts the timing of labile organic matter inputs to flow conditions more favorable for organic matter retention and in situ secondary production rather than export downstream.
Natalie Levesque (Primary Presenter/Author), Central Washington University, email@example.com;
Clay Arango ( Co-Presenter/Co-Author), Central Washington University, firstname.lastname@example.org;