Environmental Management

, Volume 50, Issue 5, pp 861–874 | Cite as

Relationships Between Nitrogen Transformation Rates and Gene Abundance in a Riparian Buffer Soil

  • Lin Wu
  • Deanna L. Osmond
  • Alexandria K. Graves
  • Michael R. Burchell
  • Owen W. Duckworth


Denitrification is a critical biogeochemical process that results in the conversion of nitrate to volatile products, and thus is a major route of nitrogen loss from terrestrial environments. Riparian buffers are an important management tool that is widely utilized to protect water from non-point source pollution. However, riparian buffers vary in their nitrate removal effectiveness, and thus there is a need for mechanistic studies to explore nitrate dynamics in buffer soils. The objectives of this study were to examine the influence of specific types of soluble organic matter on nitrate loss and nitrous oxide production rates, and to elucidate the relationships between these rates and the abundances of functional genes in a riparian buffer soil. Continuous-flow soil column experiments were performed to investigate the effect of three types of soluble organic matter (citric acid, alginic acid, and Suwannee River dissolved organic carbon) on rates of nitrate loss and nitrous oxide production. We found that nitrate loss rates increased as citric acid concentrations increased; however, rates of nitrate loss were weakly affected or not affected by the addition of the other types of organic matter. In all experiments, rates of nitrous oxide production mirrored nitrate loss rates. In addition, quantitative polymerase chain reaction (qPCR) was utilized to quantify the number of genes known to encode enzymes that catalyze nitrite reduction (i.e., nirS and nirK) in soil that was collected at the conclusion of column experiments. Nitrate loss and nitrous oxide production rates trended with copy numbers of both nir and 16s rDNA genes. The results suggest that low-molecular mass organic species are more effective at promoting nitrogen transformations than large biopolymers or humic substances, and also help to link genetic potential to chemical reactivity.


Riparian buffer Nitrogen Denitrification Quantitative PCR Nitrous oxide Nitrate 



We thank Lauren Saal, Emily Dell, Guillemo Ramirez, Sara Knies, Brad Robinson, Chris Ashwell, Greg Dick, Suzanna Bräuer, Jeff White, and John Walker. This work was supported by NC Department of Environment & Natural Resources, Conservation Reserve Enhancement Program. Lin Wu thanks the Society of Wetland Scientists for a student research grant.


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Copyright information

© Springer Science+Business Media, LLC 2012

Authors and Affiliations

  • Lin Wu
    • 1
    • 3
  • Deanna L. Osmond
    • 1
  • Alexandria K. Graves
    • 1
  • Michael R. Burchell
    • 2
  • Owen W. Duckworth
    • 1
  1. 1.Department of Soil ScienceNorth Carolina State UniversityRaleighUSA
  2. 2.Department of Biological and Agricultural EngineeringNorth Carolina State UniversityRaleighUSA
  3. 3.Department of StatisticsUniversity of North CarolinaChapel HillUSA

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