Natural abundance nitrate (NO3 −) isotopes represent a powerful tool for assessing denitrification, yet the scale and context dependence of relationships between isotopes and denitrification have received little attention, especially in surface soils. We measured the NO3 − isotope compositions in soil extractions and lysimeter water from a semi-arid meadow and lawn during snowmelt, along with the denitrification potential, bulk O2, and a proxy for anaerobic microsites. Denitrification potential varied by three orders of magnitude and the slope of δ18O/δ15N in soil-extracted NO3 − from all samples measured 1.04 ± 0.12 (R 2 = 0.64, p < 0.0001), consistent with fractionation from denitrification. However, δ15N of extracted NO3 − was often lower than bulk soil δ15N (by up to 24 ‰), indicative of fractionation during nitrification that was partially overprinted by denitrification. Mean NO3 − isotopes in lysimeter water differed from soil extractions by up to 19 ‰ in δ18O and 12 ‰ in δ15N, indicating distinct biogeochemical processing in relatively mobile water versus soil microsites. This implies that NO3 − isotopes in streams, which are predominantly fed by mobile water, do not fully reflect terrestrial soil N cycling. Relationships between potential denitrification and δ15N of extracted NO3 − showed a strong threshold effect culminating in a null relationship at high denitrification rates. Our observations of (1) competing fractionation from nitrification and denitrification in redox-heterogeneous surface soils, (2) large NO3 − isotopic differences between relatively immobile and mobile water pools, (3) and the spatial dependence of δ18O/δ15N relationships suggest caution in using NO3 − isotopes to infer site or watershed-scale patterns in denitrification.
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Bai E, Houlton BZ (2009) Coupled isotopic and process-based modeling of gaseous nitrogen losses from tropical rain forests. Glob Biogeochem Cycles 23:GB2011. doi:10.1029/2008GB003361
Bell MD, Sickman JO (2014) Correcting for background nitrate contamination in KCl-extracted samples during isotopic analysis of oxygen and nitrogen by the denitrifier method. Rapid Commun Mass Spectrom 28:520–526. doi:10.1002/rcm.6824
Billy C, Billen G, Sebilo M, Birgand F, Tournebize J (2010) Nitrogen isotopic composition of leached nitrate and soil organic matter as an indicator of denitrification in a sloping drained agricultural plot and adjacent uncultivated riparian buffer strips. Soil Biol Biochem 42:108–117. doi:10.1016/j.soilbio.2009.09.026
Brooks PD, Williams MW (1999) Snowpack controls on nitrogen cycling and export in seasonally snow-covered catchments. Hydrol Process 13:2177–2190. doi:10.1002/(SICI)1099-1085(199910)13:14/15<2177:AID-HYP850>3.0.CO;2-V
Brooks PD, Grogan P, Templer PH, Groffman P, Öquist MG, Schimel J (2011) Carbon and nitrogen cycling in snow-covered environments. Geogr Compass 5:682–699. doi:10.1111/j.1749-8198.2011.00420.x
Casciotti KL, Sigman DM, Hastings MG, Böhlke JK, Hilkert A (2002) Measurement of the oxygen isotopic composition of nitrate in seawater and freshwater using the denitrifier method. Anal Chem 74:4905–4912. doi:10.1021/ac020113w
Casciotti KL, Sigman DM, Ward BB (2003) Linking diversity and stable isotope fractionation in ammonia-oxidizing bacteria. Geomicrobiol J 20:335–353
Castellano MJ, Lewis DB, Kaye JP (2013) Response of soil nitrogen retention to the interactive effects of soil texture, hydrology, and organic matter. J Geophys Res Biogeosci 118:280–290. doi:10.1002/jgrg.20015
Chapelle FH, McMahon PB, Dubrovsky NM, Fujii RF, Oaksford ET, Vroblesky DA (1995) Deducing the distribution of terminal electron-accepting processes in hydrologically diverse groundwater systems. Water Resour Res 31:359–371
Cohen MJ, Heffernan JB, Albertin A, Martin JB (2012) Inference of riverine nitrogen processing from longitudinal and diel variation in dual nitrate isotopes. J Geophys Res Biogeosci 117:G01021. doi:10.1029/2011JG001715
Craine JM, Elmore AJ, Wang L, Augusto L, Baisden WT, Brookshire ENJ, Cramer MD, Hasselquist NJ, Hobbie EA, Kahmen A, Koba K, Kranabetter JM, Mack MC, Marin-Spiotta E, Mayor JR, McLauchlan KK, Michelsen A, Nardoto GB, Oliveira RS, Perakis SS, Peri PL, Quesada CA, Richter A, Schipper LA, Stevenson BA, Turner BL, Viani RAG, Wanek W, Zeller B (2015) Convergence of soil nitrogen isotopes across global climate gradients. Sci Rep 5:8280. doi:10.1038/srep08280
Dawson TE, Ehleringer JR (1991) Streamside trees that do not use stream water. Nature 350:335–337. doi:10.1038/350335a0
Evans RD (2001) Physiological mechanisms influencing plant nitrogen isotope composition. Trends Plant Sci 6:121–126. doi:10.1016/S1360-1385(01)01889-1
Evaristo J, Jasechko S, McDonnell JJ (2015) Global separation of plant transpiration from groundwater and streamflow. Nature 525:91–94. doi:10.1038/nature14983
Fang Y, Koba K, Makabe A, Takahashi C, Zhu W, Hayashi T, Hokari AA, Urakawa R, Bai E, Houlton BZ, Xi D, Zhang S, Matsushita K, Tu Y, Liu D, Zhu F, Wang Z, Zhou G, Chen D, Makita T, Toda H, Liu X, Chen Q, Zhang D, Li Y, Yoh M (2015) Microbial denitrification dominates nitrate losses from forest ecosystems. Proc Natl Acad Sci USA 112:1470–1474. doi:10.1073/pnas.1416776112
Galloway JN, Aber JD, Erisman JW, Seitzinger SP, Howarth RW, Cowling EB, Cosby BJ (2003) The nitrogen cascade. Bioscience 53:341–356. doi:10.1641/0006-3568(2003)053[0341:TNC]2.0.CO;2
Good SP, Noone D, Bowen G (2015) Hydrologic connectivity constrains partitioning of global terrestrial water fluxes. Science 349:175–177. doi:10.1126/science.aaa5931
Granger J, Sigman DM, Lehmann MF, Tortell PD (2008) Nitrogen and oxygen isotope fractionation during dissimilatory nitrate reduction by denitrifying bacteria. Limnol Oceanogr 53:2533–2545
Granger J, Sigman DM, Rohde MM, Maldonado MT, Tortell PD (2010) N and O isotope effects during nitrate assimilation by unicellular prokaryotic and eukaryotic plankton cultures. Geochim Cosmochim Acta 74:1030–1040. doi:10.1016/j.gca.2009.10.044
Groffman PM (2012) Terrestrial denitrification: challenges and opportunities. Ecol Process 1:1–11
Groffman PM, Holland EA, Myrold DD, Robertson GP, Zou X (1999) Denitrification. In: Robertson GP, Bledsoe CS, Coleman DC, Sollins P (eds) Standard soil methods for long-term ecological research. Oxford University Press, New York, pp 272–290
Groffman PM, Boulware NJ, Zipperer WC, Pouyat RV, Band LE, Colosimo MF (2002) Soil nitrogen cycle processes in urban riparian zones. Environ Sci Technol 36:4547–4552. doi:10.1021/es020649z
Hall SJ, Silver WL (2015) Reducing conditions, reactive metals, and their interactions can explain spatial patterns of surface soil carbon in a humid tropical forest. Biogeochemistry 125:149–165. doi:10.1007/s10533-015-0120-5
Hall SJ, McDowell WH, Silver WL (2013) When wet gets wetter: decoupling of moisture, redox biogeochemistry, and greenhouse gas fluxes in a humid tropical forest soil. Ecosystems 16:576–589. doi:10.1007/s10021-012-9631-2
Hall SJ, Weintraub SR, Eiriksson D, Brooks PD, Baker MA, Bowen GJ, Bowling DR (2016a) Stream nitrogen inputs reflect groundwater across a snowmelt-dominated montane to urban watershed. Environ Sci Technol 50:1137–1146. doi:10.1021/acs.est.5b04805
Hall SJ, Baker MA, Jones SB, Stark J, Bowling DR (2016b) Contrasting soil nitrogen dynamics across a montane meadow and urban lawn in a semi-arid watershed. Urban Ecosyst 1–19. doi:10.1007/s11252-016-0538-0 (In press)
Holmes RM, McClelland JW, Sigman DM, Fry B, Peterson BJ (1998) Measuring 15N–NH4 + in marine, estuarine and fresh waters: an adaptation of the ammonia diffusion method for samples with low ammonium concentrations. Mar Chem 60:235–243. doi:10.1016/S0304-4203(97)00099-6
Houlton BZ, Bai E (2009) Imprint of denitrifying bacteria on the global terrestrial biosphere. Proc Natl Acad Sci USA 106:21713–21716. doi:10.1073/pnas.0912111106
Houlton BZ, Sigman DM, Hedin LO (2006) Isotopic evidence for large gaseous nitrogen losses from tropical rainforests. Proc Natl Acad Sci USA 103:8745–8750. doi:10.1073/pnas.0510185103
Kendall C, Elliott EM, Wankel SD (2007) Tracing anthropogenic inputs of nitrogen to ecosystems. In: Michener R, Lajtha K (eds) Stable isotopes in ecology and environmental science. Blackwell, London, pp 375–449
Kool DM, Wrage N, Oenema O, Van Kessel C, Van Groenigen JW (2011) Oxygen exchange with water alters the oxygen isotopic signature of nitrate in soil ecosystems. Soil Biol Biochem 43:1180–1185. doi:10.1016/j.soilbio.2011.02.006
Kulkarni MV, Groffman PM, Yavitt JB (2008) Solving the global nitrogen problem: it’s a gas! Front Ecol Environ 6:199–206. doi:10.1890/060163
Landon MK, Delin GN, Komor SC, Regan CP (1999) Comparison of the stable-isotopic composition of soil water collected from suction lysimeters, wick samplers, and cores in a sandy unsaturated zone. J Hydrol 224:45–54. doi:10.1016/S0022-1694(99)00120-1
Lehmann MF, Reichert P, Bernasconi SM, Barbieri A, McKenzie JA (2003) Modelling nitrogen and oxygen isotope fractionation during denitrification in a lacustrine redox-transition zone. Geochim Cosmochim Acta 67:2529–2542. doi:10.1016/S0016-7037(03)00085-1
Mariotti A, Germon JC, Hubert P, Kaiser P, Letolle R, Tardieux A, Tardieux P (1981) Experimental determination of nitrogen kinetic isotope fractionation: some principles; illustration for the denitrification and nitrification processes. Plant Soil 62:413–430. doi:10.1007/BF02374138
Mayer B, Bollwerk SM, Mansfeldt T, Hütter B, Veizer J (2001) The oxygen isotope composition of nitrate generated by nitrification in acid forest floors. Geochim Cosmochim Acta 65:2743–2756. doi:10.1016/S0016-7037(01)00612-3
Michalski G, Meixner T, Fenn M, Hernandez L, Sirulnik A, Allen E, Thiemens M (2004) Tracing atmospheric nitrate deposition in a complex semiarid ecosystem using ∆17O. Environ Sci Technol 38:2175–2181. doi:10.1021/es034980+
Parkin T, Starr J, Meisinger J (1987) Influence of sample size on measurement of soil denitrification. Soil Sci Soc Am J 51:1492–1501
Petersen DG, Blazewicz SJ, Firestone M, Herman DJ, Turetsky M, Waldrop M (2012) Abundance of microbial genes associated with nitrogen cycling as indices of biogeochemical process rates across a vegetation gradient in Alaska. Environ Microbiol 14:993–1008. doi:10.1111/j.1462-2920.2011.02679.x
Raciti SM, Burgin AJ, Groffman PM, Lewis DN, Fahey TJ (2011) Denitrification in suburban lawn soils. J Environ Qual 40:1932. doi:10.2134/jeq2011.0107
Riha KM, Michalski G, Gallo EL, Lohse KA, Brooks PD, Meixner T (2014) High atmospheric nitrate inputs and nitrogen turnover in semi-arid urban catchments. Ecosystems 17:1309–1325. doi:10.1007/s10021-014-9797-x
Roach WJ, Grimm NB (2011) Denitrification mitigates N flux through the stream–floodplain complex of a desert city. Ecol Appl 21:2618–2636. doi:10.1890/10-1613.1
Schaetzl RJ, Anderson S (2005) Soils: genesis and geomorphology. Cambridge University Press, Cambridge
Sebilo M, Billen G, Grably M, Mariotti A (2003) Isotopic composition of nitrate-nitrogen as a marker of riparian and benthic denitrification at the scale of the whole Seine River system. Biogeochemistry 63:35–51. doi:10.1023/A:1023362923881
Sexstone A, Revsbech N, Parkin T, Tiedje J (1985) Direct measurement of oxygen profiles and denitrification rates in soil aggregates. Soil Sci Soc Am J 49:645–651
Sigman DM, Granger J, DiFiore PJ, Lehmann MM, Ho R, Cane G, van Geen A (2005) Coupled nitrogen and oxygen isotope measurements of nitrate along the eastern North Pacific margin. Glob Biogeochem Cycles 19:GB4022. doi:10.1029/2005GB002458
Sonderegger D (2012) SiZer: Significant Zero Crossings. R package version 0.1-4. http://CRAN.R-project.org/package=SiZer. Accessed 1 Oct 2015
Wells NS, Baisden WT, Clough TJ (2015) Ammonia volatilisation is not the dominant factor in determining the soil nitrate isotopic composition of pasture systems. Agric Ecosyst Environ 199:290–300. doi:10.1016/j.agee.2014.10.001
Wexler SK, Goodale CL, McGuire KJ, Bailey SW, Groffman PM (2014) Isotopic signals of summer denitrification in a northern hardwood forested catchment. Proc Natl Acad Sci 111:16413–16418. doi:10.1073/pnas.1404321111
Yang WH, Teh YA, Silver WL (2011) A test of a field-based 15N–nitrous oxide pool dilution technique to measure gross N2O production in soil. Glob Change Biol 17:3577–3588. doi:10.1111/j.1365-2486.2011.02481.x
Zak DR, Groffman PM, Pregitzer KS, Christensen S, Tiedje JM (1990) The vernal dam: plant–microbe competition for nitrogen in northern hardwood forests. Ecology 71:651–656. doi:10.2307/1940319
The manuscript was greatly improved by critical feedback from Jason Kaye and two anonymous reviewers. We gratefully acknowledge field and lab assistance from Simone Jackson, Jillian Turner, Dave Eiriksson, Kendalynn Morris, and contributions from Suvankar Chakraborty, Gabe Bowen, and Jim Ehleringer in implementing the denitrifier method at SIRFER. This research was supported by NSF EPSCoR grant IIA 1208732 awarded to Utah State University, as part of the State of Utah Research Infrastructure Improvement Award, and by NSF grant DBI-1337947. Any opinions, findings, and conclusions or recommendations expressed are those of the author(s) and do not necessarily reflect the views of the National Science Foundation.
Author contribution statement
S.J.H. designed the study, S.R.W. and D.R.B. contributed to sample analysis and interpretation, and S.J.H. wrote the paper with contributions from S.R.W. and D.R.B.
Communicated by Jason P. Kaye.
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Hall, S.J., Weintraub, S.R. & Bowling, D.R. Scale-dependent linkages between nitrate isotopes and denitrification in surface soils: implications for isotope measurements and models. Oecologia 181, 1221–1231 (2016). https://doi.org/10.1007/s00442-016-3626-1
- Isotope mass balance model
- Mobile water