Hydrologic and Biogeochemical Drivers of Riparian Denitrification in an Agricultural Watershed
This study investigated drivers of denitrification and overall NO3− removal in an agricultural riparian area in central New York. Denitrification was measured using an in situ “push-pull” method with 15N–NO3− as a tracer during summer and fall 2011 at a pair of riparian sites characterized by different hydrologic regimes. Median denitrification rates were 1347 and 703 μg N kg soil−1 day−1 for the two study sites. These rates are higher than those reported for other riparian areas, emphasizing the role of some riparian areas as hotspots of NO3− removal. N2O production was significantly higher at one site, demonstrating that riparian areas can be a greenhouse gas source under certain conditions. Denitrification was negatively correlated with groundwater flux, suggesting that slower flushing of water, and thus longer residence time, promotes denitrification. A mass balance of NO3− loss revealed that denitrification only accounted for 5–12 % of total NO3− loss, and production of NH4+ indicated that dissimilatory NO3− reduction to NH4+ (DNRA) may be occurring at both sites. While both sites were characterized by high NO3− removal, differences in denitrification rates and NO3− removal processes demonstrate the need to improve our ability to capture spatial and process heterogeneity in landscape biogeochemical models.
KeywordsDenitrification DNRA Water quality Nitrogen cycling Riparian systems Ecohydrology Riparian groundwater
- Cornell University Agricultural Experiment Station (CUAES) (2013). ‘Homer C. Thompson Vegetable Farm.’ http://cuaes.cornell.edu/ag-operations/freeville-farm/ Accessed 11 March 2013.
- Dubrovsky, N. M., Burow, K. R., Clark, G. M., Gronberg, J. M., Hamilton, P. A., Hitt, K. J., et al. (2010). The quality of our nation’s water: nutrients in the nation’s streams and groundwater, 1992–2004. US Geological Survey Circular, 1350, 174.Google Scholar
- Groffman, P. M., Butterbach-Bahl, K., Fulweiler, R. W., Gold, A. J., Morse, J. L., Stander, E. K., et al. (2009). Challenges to incorporating spatially and temporally explicit phenomena (hotspots and hot moments) in denitrification models. Biogeochemistry, 93, 49–77. doi:10.1007/s10533-008-9277-5.CrossRefGoogle Scholar
- Hedin, L. O., von Fischer, J. C., Ostrom, N. E., Kennedy, B. P., Brown, M. G., & Robertson, G. P. (1998). Thermodynamic constraints on nitrogen transformations and other biogeochemical processes at soil-stream interfaces. Ecology, 79(2), 684–703.Google Scholar
- Jencso, K. G., McGlynn, B. L., Gooseff, M. N., Bencala, K. E., & Wondzell, S. M. (2010). Hillslope hydrologic connectivity controls riparian groundwater turnover: implications of catchment structure for riparian buffering and stream water sources. Water Resources Research, 46, W10524. doi:10.1029/2009WR008818.CrossRefGoogle Scholar
- Mosier, A. R., & Klemedtsson, L. (1994). Measuring denitrification in the field. In R. W. Weaver et al. (Eds.), Methods of soil analysis, part 2: microbiological and biochemical properties (2nd ed.). Madison: SSSA.Google Scholar
- National Resource Conservation Service (NRCS). (2013). Web Soil Survey. http://websoilsurvey.nrcs.usda.gov/app/HomePage.htm Accessed 11 March 2013.
- Northeast Regional Climate Center (NRCC) (2013), The Ithaca Climate Page, http://www.nrcc.cornell.edu/climate/ithaca/, Accessed 11 March 2013.
- Robertson, G. P., Sollins, P., Ellis, B. G., & Lajtha, K. (1999). Exchangeable ions, pH and cation exchange capacity. In G. P. Robertson et al. (Eds.), Standard soil methods for long-term ecological research. New York: Oxford University Press.Google Scholar
- Santisteban, J. I., Mediavilla, R., Lopez-Pamo, E., Dabrio, C. J., Ruiz Zapata, M. B., Gil Garcıa, M. J., et al. (2004). Loss on ignition: a qualitative or quantitative method for organic matter and carbonate mineral content in sediments? Journal of Paleolimnology, 32, 287–299.CrossRefGoogle Scholar
- Tiedje, J. M. (1994). Denitrifiers. In R. W. Weaver et al. (Eds.), Methods of soil analysis, part 2: microbiological and biochemical properties (2nd ed.). Madison: SSSA.Google Scholar
- Townsend, A.R., Martinelli, L.A., & Howarth, R.W. (2009). The global nitrogen cycle, biodiversity, and human health. In: Biodiversity change and human health: from ecosystem services to spread of disease. SCOPE, Paris, France.Google Scholar
- Triska, F. J., Duff, J. H., Sheibley, R. W., Jackman, A. P., & Avanzino, R. J. (2007). DIN retention-transport through four hydrologically connected zones in a headwater catchment of the Upper Mississippi River. Journal of the American Water Resources Association, 43(1), 60–71.CrossRefGoogle Scholar
- United States Environmental Protection Agency (US EPA) (1990). National pesticide survey: nitrate. Office of Water, Office of Pesticides and Toxic Substances. Washington, D.C.Google Scholar
- United States Environmental Protection Agency (US EPA) (2005). Riparian buffer width, vegetative cover, and nitrogen removal effectiveness: a review of current science and regulations. EPA/600/R-05/118, Office of Research and Development, Washington DC.Google Scholar
- Zaman, M., Nguyen, M. L., Gold, A. J., Groffman, P. M., Kellogg, D. Q., & Wilcock, R. J. (2008). Nitrous oxide generation, denitrification, and nitrate removal in a seepage wetland intercepting surface and subsurface flows from a grazed dairy catchment. Australian Journal of Soil Research, 46, 565–577.CrossRefGoogle Scholar