PARENT SESSION
Poster Session # 13: Biogeochemistry, Photosynthesis, and Respiration.
Tuesday, August 5 Presentation from 5:00 PM to 6:30 PM. SITCC Exhibit Hall B.
Assessment of aboveground litter decomposition rates across a hydrologic gradient in bottomland hardwood forest.
Marse, Todd*,1, Whitbeck, Julie1, 1 University of New Orleans, New Orleans, LA, USA
ABSTRACT- We estimate aboveground litter decomposition rates across a 1.0-m elevation gradient in mature bottomland hardwood forest in Jean Lafitte National Historical Park and Preserve, Jefferson Parish, Louisiana, USA. Hydrology changes significantly along this gradient, such that the high elevation is rarely flooded, while the low elevation experiences standing water for several months each year. We hypothesized that litter decomposition rate would be slowest at the wet end of this gradient, and that dry summer conditions at the high elevation site would also diminish the rate of decomposition. To assess aboveground decomposition rates, we measured litter mass change over time by placing known quantities of oven-dried litter into fiberglass screen bags and deploying the bags on the forest floor for varying exposure intervals. We placed groups of litter bags at five randomly chosen replicate locations at each of three sites (ridge, intermediate, swamp) along the hydrologic gradient. To estimate initial decomposition rates, we collected litter bags each month for six months, then bi-monthly to one year. We plan additional sampling at 15, 18, and 24 months after installation to assess longer-term rates. The data for the first three months of collection indicate a steady decrease in mass at the wettest site (swamp) with a decomposition rate of 0.03 g dw per day. We observed an unexpected increase in mass during the first 60 days at the drier sites (ridge and intermediate), which was then followed by a decrease similar to that observed at the swamp site. Close inspection of litter collected from the ridge and intermediate sites suggests that one or more organisms may be using the leaf litter at these sites as a substrate, adding mass to the litter.
Key words: decomposition, carbon cycling, bottomland hardwood forest, hydrology