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SFS Annual Meeting

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NITROGEN BY HERBIVORY EXPERIMENT ON LAND ALTERS LITTER CHEMISTRY AND SUBSEQUENT IN-STREAM LITTER DECOMPOSITION

Terrestrial herbivores can influence the chemistry and timing of leaf litter inputs to both terrestrial and aquatic systems. The concentrations of nutrients available to plants can partially determine their defensive responses to herbivory which can also alter litter chemistry. Together, these two terrestrial factors may alter organic matter processing rates in streams that are reliant on carbon and nutrients from riparian leaf litter. Sitka willow (Salix sitchensis) at Mount St. Helens are heavily infested with the introduced stem-boring weevil (Cryptorhynchus lapathi; Coleoptera: Curculionidae) and attacked plants show branch die-back and early litterfall. Using an established factorial experimental garden that manipulated the nitrogen inputs and restricted weevil infection to some plants for over 10 years, we found that nitrogen addition had strong effects on litter chemistry and led to decreasing condensed tannins as defense compounds. In addition, we found that litter mass loss in the stream was significantly influenced by both increasing N-addition and increasing condensed tannins. In the early-succession stream systems of Mount St. Helens, the direct influence of nutrient limitation seems to more strongly influence litter dynamics than indirect effects of a hyper-abundant introduced weevil herbivore.

Jordan Moffett (Co-Presenter/Co-Author), The Evergreen State College, mofjor15@evergreen.edu;


Logan Lancaster (Co-Presenter/Co-Author), The Evergreen State College, lanlog02@evergreen.edu;


Lauren Walker (Co-Presenter/Co-Author), Lewis and Clark College, laurenwalker@lclark.edu;


Joy Ramstack Hobbs (Co-Presenter/Co-Author), The Evergreen State College, hobbsj@evergreen.edu;


Shannon Claeson (Co-Presenter/Co-Author), USDA Forest Service, sclaeson@fs.fed.us;


John Bishop (Co-Presenter/Co-Author), Washington State University, bishopj@wsu.edu;


Mailea Miller-Pierce (Co-Presenter/Co-Author), Washington State University, m.miller-pierce@wsu.edu;


Carri LeRoy (Primary Presenter/Author), Evergreen State College, leroyc@evergreen.edu;