PARENT SESSION
Poster Session 2: Forest Ecology
Monday, August 8, 5:00 PM - 6:30 PM, Exhibit Hall 220 A-E, Level 2, Palais des congrès de Montréal
Stand-level control of nitrogen cycling and decomposition by oak and sugar maple at Mammoth Cave National Park.
Fabio, Eric*,1, Arthur, Mary1, 1 University of Kentucky, Lexington, KY
ABSTRACT- Species composition is often a significant factor in determining rates of nutrient cycling in temperate forest ecosystems. This is attributed to the quality of litter inputs, as well as the soil biotic community adapted to a particular source of energy and nutrients. Nutrient release is dependent upon decomposition rates, which in turn is a function of moisture availability and litter quality. At Mammoth Cave National Park, tree species distribution is controlled by moisture availability, and N cycling rates are strongly correlated with species composition. Stands dominated by a suite of oak species have the lowest rates of nitrification; in stands where sugar maple is a more important component, nitrification increases substantially, resulting in soil solution nitrate concentrations that are much higher compared to the oak-dominated stands. Oak stands produce poor-quality litter that is resistant to decomposition, whereas maple stands produce litter with a lower C:N ratio, more favorable for decomposition. Initial results from a reciprocal transplant decomposition study show that maple litter in maple stands decomposes faster than maple litter in oak stands, but oak litter decomposes faster in oak stands. These results suggest differences in microbial communities between stand types. A common substrate decomposition experiment and laboratory assessments of microbial biomass and respiration with N additions of varying levels will further elucidate differences in microbial communities and their response to increased N availability. These findings are important as N deposition rates to the park are among the highest in the region, and newly proposed coal-burning power plants are slated for construction upwind of the park. With poor oak regeneration in the mid-story and potential replacement by maple species, shifts in litter quality and microbial communities at the stand level could have major implications for the release of N into important aquatic systems.
Key words: nitrogen cycling, decomposition, Quercus spp., Acer saccharum