PARENT SESSION
Poster Session 37: Forest Ecology.
Thursday, August 5 Presentations from 5:00 PM to 6:30 PM, Exhibit Hall A 1.
Nitrogen and carbon inputs from canopy herbivores : Comparing outbreak and endemic levels of herbivory.
Reynolds, Barbara1, Hunter, Mark2, 1 University of North Carolina - Asheville, Asheville, NC2 University of Georgia, Athens, GA
ABSTRACT- Frass inputs from canopy herbivores were collected and measured in twenty plots on each of three sites along an elevation gradient at Coweeta Hydrologic Laboratory (USFS) in western North Carolina USA. Twentyfour hr collections were made 2 to 3 times per month throughout the growing season for three years. Frass from individual plots per date was analyzed for percent nitrogen and percent total carbon, and the CN ratio was determined for each sample. Average values for these three categories, plus the weight of frass, were calculated for each date and extrapolated to g per hectare per 24 hours. Frass deposition generally showed two pronounced peaks on the mid and high elevation sites, coinciding with leaf flush early in the growing season, and a second peak late in the growing season. At the low elevation site, the most prominent peak was in the mid to later part of the growing season, and varied with the year. Frass inputs during a short, chronic, outbreak of sawflies (Periclista sp.) on the high elevation site were almost twice those measured at other times or sites. Nitrogen deposition followed the same pattern as frass depostion. Frass CN generally increased over time for all elevations, except the low elevation in 1996, but showed considerable variation among collections. Nitrogen content in frass from the high elevation outbreak led to significantly higher amounts of stream nitrate compared to previous, non outbreak, years or to the control stream.
Key words: frass, outbreak, herbivory, nutrients