PARENT SESSION
Oral Session #40: Biodiversity and Ecosystem Function: Do species and species richness matter?. Presiding: R. Dirzo.
Wednesday, August 8, 2001. 8:00 AM to 12:00 PM. Madison Ballroom D.
Decomposition and nutrient cycling in a changing environment: Is genetic diversity redundant to ecosystem function?
Madritch, Michael1, Hunter, Mark1, 1
ABSTRACT- Anthropogenic forces are concurrently altering global carbon and nitrogen cycles while reducing biological diversity. Our study addresses how a loss of intraspecific genetic diversity affects the fluxes of carbon and nitrogen in an ecosystem. Leaf secondary metabolites which partially control decomposition vary within species according to genotype and environment. We are studying the relative effects of genetic diversity of Quercus laevis leaf litter and environmental factors on decomposition. Using previously genotyped individuals, we have collected specific phenotypes of litter and established a three-year decomposition study with treatments varying in intraspecific litter diversity. Initial litter chemistry of randomly chosen phenotypes shows partial genetic control of condensed tannins and C:N ratios. The first 18 months of data show a significant effect of litter phenotype on decomposition and nitrogen fluxes. Immobilization of carbon and nitrogen in the litter differed among phenotypes, while overall decomposition remained low. There was no apparent universal effect of decreased phenotypic diversity; single phenotype litters did not invoke similar responses compared to a mixed litter treatment. However, there were large and significant variations in carbon and nitrogen fluxes among litter phenotypes, suggesting that litter genotype affects carbon and nitrogen cycling through secondary chemistry. In the short term, the decomposer community is not able to compensate for reductions in intraspecific diversity of Q. laevis litter. Consequently, carbon and nitrogen cycles are significantly different between single phenotype and mixed phenotype treatments.
KEY WORDS: biodiversity, decomposition, nitrogen