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WESTERN SPRUCE BUDWORM HERBIVORY INCREASES THROUGHFALL NUTRIENTS BUT NOT LITTER DECOMPOSITION RATES

Western spruce budworm outbreaks should intensify in coniferous Pacific Northwest forests as climate change causes shorter winters and hotter summers. Budworm defoliation could accelerate litter decomposition rates by increasing frass input to the forest floor followed by nutrient leaching and/or by stimulating nutrient losses from the canopy via leaching. In forest plots with and without budworms, we deployed native coniferous and non-native deciduous litter bags for one year to measure decomposition rates, and we collected throughfall for nutrient analysis. Budworm sites had higher net throughfall flux of soluble reactive phosphorus and ammonium (paired t-test, p<0.01), but dissolved organic carbon flux did not differ. Despite added nutrient inputs from budworms, litter decomposition rates did not differ between high and low budworm sites, although deciduous litter decomposed faster than coniferous litter (ANOVA, p<<0.001). Limited moisture from extended summer drought in this climate could regulate decomposition rather than nutrients. These results imply limited ability of microbial immobilization to buffer budworm nutrient inputs to litter, suggesting that nutrients infiltrate into soils with possible consequences for altered nutrient cycling rates and elemental export from watersheds.

Izak Neziri (Primary Presenter/Author), Central Washington University, izakneziri@gmail.com;


Clay Arango ( Co-Presenter/Co-Author), Central Washington University, arangoc@cwu.edu;


Sally Entrekin ( Co-Presenter/Co-Author), University of Central Arkansas , sentrekin@uca.edu;


Jennifer Lipton ( Co-Presenter/Co-Author), Central Washington University, liptonj@cwu.edu;


Alexandra Ponette-González ( Co-Presenter/Co-Author), University of North Texas, Alexandra.Ponette@unt.edu;