PARENT SESSION
Oral Session #59: Soil Ecology: Microbial and Invertebrate.
Presiding: M. Rillig
Wednesday, August 7. 8:00 AM to 11:30 AM. Palo Verde Room, Radisson.
Effects of denitrifier community structure on N2O and N2 gas flux in a nitrogen fertilization experiment.
Wallenstein, Matt*,1,2, Schlesinger, William2, 1 Duke University, Durham, NC, United States2 Duke University, Durham, NC, United States
ABSTRACT- Nitrogen fertilization has been shown to increase denitrification rates in a variety of ecosystems, yet few studies have examined both N2O and N2 fluxes in response to changes in nitrogen cycling. The effects of altered rates of nitrogen cycling on denitrification are partly explained by changes in the soil environment. However, few studies have examined the role of microbial community structure in controlling denitrification. Using soil collected from the Long Term Soil Productivity experiment at the Fernow Experimental Forest in West Virginia, USA, we tested the effects of fertilization and liming on rates of N2O and N2 emissions using laboratory incubations, and denitrifier community structure based on genomic DNA extracted from field soil. Primers specific for the nitrite reductase gene (NirK and NirS) and the nitrous oxide reductase gene (Nos) were used to quantify the relative abundance of those genes by Real-Time PCR. We also used probes generated by PCR to quantify the presence of denitrifying genes using slot-blot hybridization. We found a positive correlation between NirK and NirS relative abundance and N2O production and between Nos abundance and N2 production. Our results suggest that denitrifier community structure exerts some control on rates of denitrification, though their activity is also modulated by substrate availability and environmental conditions.
KEY WORDS: denitrification, microbial community structure, real-time PCR, nitrogen saturation