PARENT SESSION
Oral Session #33: Biodiversity and Ecosystem Function: Nutrients, soils, microbes.
Presiding: K. Brown
Tuesday, August 6. 8:00 AM to 11:30 AM. Grand Ballroom Central, Radisson.
Interactive effects of intraspecific litter diversity and nitrogen deposition on nutrient cycling.
MADRITCH, MICHAEL*,1, HUNTER, MARK1, 1 University of Georgia, Athens, GA
ABSTRACT- Anthropogenic forces are concurrently reducing biodiversity and altering terrestrial nutrient cycles. We present results from experiments that simulated both the decline in biodiversity and the increase in atmospheric nitrogen deposition. As natural population sizes decrease, genetic diversity within a single species also declines. The consequences of genetic loss for ecosystem functioning are poorly understood, and interactions among intraspecific diversity, nitrogen deposition, and nutrient cycling are unknown. In a field experiment, we varied the intraspecific leaf litter diversity of Quercus laevis in an oak sandhills community and monitored ecosystem responses. Intraspecific diversity affected carbon and nitrogen cycles during decomposition through genetically-mediated litter chemistries. Mass loss, changes in litter carbon and nitrogen content, as well as soil ammonium availability were all affected by intraspecific litter diversity. The effects on both carbon and nitrogen cycles were significant, but not uniform in the direction of change. In a parallel laboratory microcosm experiment, we tested the effects of intraspecific litter diversity and nitrogen deposition on ecosystem processes. Intraspecific diversity increased soil respiration overall, with the greatest increases in respiration occurring under high nitrogen deposition. In contrast, intraspecific diversity had little impact on the amount of nitrogen leached during simulated nitrogen deposition. Nitrogen deposition increased the amount of inorganic nitrogen leached, while the amount of dissolved organic nitrogen leached remained constant regardless of litter diversity or nitrogen deposition treatment. Our results demonstrate the potential for losses in genetic diversity to interact with other global environmental changes to influence terrestrial nutrient cycles.
KEY WORDS: biodiversity, ecosystem function, intraspecific diversity, nitrogen deposition