Abstract
Wetlands have an inordinate influence on the global greenhouse gas budget, but how global changes may alter wetland contribution to future greenhouse gas fluxes is poorly understood. We determined the greenhouse gas balance of a tidal marsh exposed to nine years of experimental carbon dioxide (CO2) and nitrogen (N) manipulation. We estimated net carbon (C) gain rates by measuring changes in plant and soil C pools over nine years. In wetland soils that accrete primarily through organic matter inputs, long-term measurements of soil elevation, along with soil C density, provide a robust estimate of net soil C gain. We used net soil C gain along with methane and nitrous oxide fluxes to determine the radiative forcing of the marsh under elevated CO2 and N addition. Nearly all plots exhibited a net gain of C over the study period (up to 203 g C m−2 year−1), and C gain rates were greater with N and CO2 addition. Treatment effects on C gain and methane emissions dominated trends in radiative forcing while nitrous oxide fluxes in all treatments were negligible. Though these soils experience salinities that typically suppress methane emissions, our results suggest that elevated CO2 can stimulate methane emissions, overcoming positive effects of elevated CO2 on C gain, converting brackish marshes that are typically net greenhouse gas sinks into sources. Adding resources, either CO2 or N, will likely increase “blue carbon” accumulation rates in tidal marshes, but importantly, each resource can have distinct influences on the direction of total greenhouse forcing.







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Alam MS, Jia Z (2012) Inhibition of methane oxidation by nitrogenous fertilizers in a paddy soil. Front Microbiol 3(246):1–13
Anisfeld SC, Hill TD (2012) Fertilization effects on elevation change and belowground carbon balance in a Long Island Sound tidal marsh. Estuaries Coasts 35(1):201–211
Barnard R, Leadley PW, Hungate BA (2005) Global change, nitrification, and denitrification: a review. Glob Biogeochem Cycles 19(1):1–13
Bodelier PLE, Laanbroek HJ (2004) Nitrogen as a regulatory factor of methane oxidation in soils and sediments. FEMS Microbiol Ecol 47(3):265–277
Bowden WB (1986) Gaseous nitrogen emmissions from undisturbed terrestrial ecosystems: an assessment of their impacts on local and global nitrogen budgets. Biogeochemistry 2(3):249–279
Brown JR, Blankinship JC, Niboyet A, van Groenigen KJ, Dijkstra P, Le Roux X, Leadley PW, Hungate BA (2012) Effects of multiple global change treatments on soil N2O fluxes. Biogeochemistry 109(1–3):85–100
Chmura GL, Anisfeld SC, Cahoon DR, Lynch JC (2003) Global carbon sequestration in tidal, saline wetland soils. Glob Biogeochem Cycles 17(4):1–12
Collins M, Knutti R, Arblaster JM, Dufresne JL, Fichefet T, Friedlingstein P, Gao X, Gutowski WJ, Johns T, Krinner G (2013) Long-term climate change: projections, commitments and irreversibility. In: Climate change 2013: the physical science basis. contribution of working group i to the fifth assessment report of the intergovernmental panel on climate change [Stocker TF, Qin D, Plattner G-K, Tignor M, Allen SK, Boschung J, Nauels A, Xia Y, Bex V, Midgley PM (eds.)]. Cambridge University Press, Cambridge, United Kingdom and New York, NY, USA
Conrad R, Rothfuss F (1991) Methane oxidation in the soil surface layer of a flooded rice field and the effect of ammonium. Biol Fertil Soils 12(1):28–32
Dacey JWH, Drake BG, Klug MJ (1994) Stimulation of methane emission by carbon dioxide enrichment of marsh vegetation. Nature 340(6484):47–49
Deegan LA, Johnson DS, Warren RS, Peterson BJ, Fleeger JW, Fagherazzi S, Wollheim WM (2012) Coastal eutrophication as a driver of salt marsh loss. Nature 490(7420):388–392
Doughty CL, Langley JA, Walker WS, Feller IC, Schaub R, Chapman SK (2015) Mangrove range expansion rapidly increases coastal wetland carbon storage. Estuaries Coasts 39(2):385–396
Graham SA, Mendelssohn IA (2014) Coastal wetland stability maintained through counterbalancing accretionary responses to chronic nutrient enrichment. Ecology 95(12):3271–3283
Gulledge J, Schimel JP (1998) Low-concentration kinetics of atmospheric CH4 oxidation in soil and mechanism of NH4 + inhibition. Appl Environ Microbiol 64(11):4291–4298
Hamersley MR, Howes BL (2005) Coupled nitrification-denitrification measured in situ in a Spartina alterniflora marsh with a 15NH4 + tracer. Mar Ecol Prog Ser 299:123–135
Hartmann, DL, Klein Tank AMG, Rusticucci M, Alexander LV, Brönnimann S, Charabi Y, Dentener FJ, Dlugokencky EJ, Easterling DR, Kaplan A, Soden BJ, Thorne PW, Wild M, Zhai PM (2013) Observations: atmosphere and surface. In: Climate change 2013: the physical science basis. Contribution of working group I to the fifth assessment report of the intergovernmental panel on climate change [Stocker TF, Qin D, Plattner G-K, Tignor M, Allen SK, Boschung J, Nauels A, Xia Y, Bex V, Midgley PM (eds.)]. Cambridge University Press, Cambridge, United Kingdom and New York, NY, USA
Irvine IC, Vivanco L, Bentley PN, Martiny JBH (2012) The effect of nitrogen enrichment on C1-cycling microorganisms and methane flux in salt marsh sediments. Front Microbiol 3(90):142–151
Keller JK, Wolf AA, Weisenhorn PB, Drake BG, Megonigal JP (2009) Elevated CO2 affects porewater chemistry in a brackish marsh. Biogeochemistry 96(1):101–117
Kemp WM, Boynton WR, Adolf JE, Boesch DF, Boicourt WC, Brush G, Cornwell JC, Fisher TR, Glibert PM, Hagy JD (2005) Eutrophication of Chesapeake Bay: historical trends and ecological interactions. Mar Ecol Prog Ser 303(21):1–29
Kinney EL, Valiela I (2013) Changes in δ15N in salt marsh sediments in a long-term fertilization study. Mar Ecol Prog Ser 477:41–52
Kirwan ML, Guntenspergen GR (2012) Feedbacks between inundation, root production, and shoot growth in a rapidly submerging brackish marsh. J Ecol 100(3):764–770
Langley JA, Megonigal JP (2010) Ecosystem response to elevated CO2 levels limited by nitrogen-induced plant species shift. Nature 466(7302):96–99
Langley JA, McKee KL, Cahoon DR, Cherry JA, Megonigal JP (2009a) Elevated CO2 stimulates marsh elevation gain, counterbalancing sea-level rise. Proc Natl Acad Sci 106(15):6182–6186
Langley JA, Sigrist MV, Duls J, Cahoon DR, Lynch JC, Megonigal JP (2009b) Global change and marsh elevation dynamics: experimenting where land meets sea and biology meets geology. Smithson Contrib Mar Sci 38:391–400
Langley JA, Mozdzer TJ, Shepard KA, Hagerty SB, Patrick Megonigal J (2013) Tidal marsh plant responses to elevated CO2, nitrogen fertilization, and sea level rise. Glob Change Biol 19(5):1495–1503
Le Mer J, Roger P (2001) Production, oxidation, emission and consumption of methane by soils: a review. Eur J Soil Biol 37(1):25–50
Liu L, Greaver TL (2009) A review of nitrogen enrichment effects on three biogenic GHGs: the CO2 sink may be largely offset by stimulated N2O and CH4 emission. Ecol Lett 12(10):1103–1117
Marsh AS, Rasse DP, Drake BG, Megonigal JP (2005) Effect of elevated CO2 on carbon pools and fluxes in a brackish marsh. Estuaries 28(5):694–704
McLeod E, Chmura GL, Bouillon S, Salm R, Björk M, Duarte CM, Lovelock CE, Schlesinger WH, Silliman BR (2011) A blueprint for blue carbon: toward an improved understanding of the role of vegetated coastal habitats in sequestering CO2. Front Ecol Environ 9(10):552–560
Megonigal JP, Schlesinger WH (1997) Enhanced CH4 emission from a wetland soil exposed to elevated CO2. Biogeochemistry 37(1):77–88
Megonigal JP, Schlesinger W (2002) Methane-limited methanotrophy in tidal freshwater swamps. Glob Biogeochem Cycles 16(4):1–10
Morris JT, Bradley PM (1999) Effects of nutrient loading on the carbon balance of coastal wetland sediments. Limnol Oceanogr 44(3):699–702
Morris JT, Nyman JA, Shaffer GP (2014) The influence of nutrients on the coastal wetlands of the Mississippi delta. Perspectives on the restoration of the Mississippi Delta. Springer, Netherlands, pp 111–123
Mou X, Liu X, Tong C, Sun Z (2014) Responses of CH4 emissions to nitrogen addition and Spartina alterniflora invasion in Minjiang River estuary, southeast of China. Chin Geogr Sci 24(5):562–574
Myhre G, Shindell D, Bréon F-M, Collins W, Fuglestvedt JS, Huang J, Koch D, Lamarque J-F, Lee D, Mendoza B, Nakajima T, Robock A, Stephens G, Takemura T, Zhang H (2013) Anthropogenic and natural radiative forcing. In: Climate change 2013: the physical science basis. Contribution of working group I to the fifth assessment report of the intergovernmental panel on climate change. Cambridge [Stocker TF, Qin D, Plattner G-K, Tignor M, Allen SK, Boschung J, Nauels A, Xia Y, Bex V, Midgley PM (eds.)]. Cambridge University Press, Cambridge, United Kingdom and New York, NY, USA. pp 659–740
Neubauer SC, Megonigal JP (2015) Moving beyond global warming potentials to quantify the climatic role of ecosystems. Ecosystems 18(6):1000–1013
Niboyet A, Le Roux X, Dijkstra P, Hungate BA, Barthes L, Blankinship JC, Brown JR, Field CB, Leadley PW (2011) Testing interactive effects of global environmental changes on soil nitrogen cycling. Ecosphere 2(5): art56
Olsson L, Ye S, Yu X, Wei M, Krauss KW, Brix H (2015) Factors influencing CO2 and CH4 emissions from coastal wetlands in the Liaohe Delta, Northeast China. Biogeosci Discuss 12(4):3469–3503
Orr CH, Predick KI, Stanley EH, Rogers KL (2014) Spatial autocorrelation of denitrification in a restored and a natural floodplain. Wetlands 34(1):89–100
Pastore MA, Megonigal JP, Langley JA (2016) Elevated CO2 promotes long-term nitrogen accumulation only in combination with nitrogen addition. Glob Change Biol 22(1):391–403
Pendleton L, Donato DC, Murray BC, Crooks S, Jenkins WA, Sifleet S, Craft C, Fourqurean JW, Kauffman JB, Marbà N (2012) Estimating global “blue carbon” emissions from conversion and degradation of vegetated coastal ecosystems. PLoS ONE 7(9):e43542
Poffenbarger HJ, Needelman BA, Megonigal JP (2011) Salinity influence on methane emissions from tidal marshes. Wetlands 31(5):831–842
R Core Team (2013) R: a language and environment for statistical computing. R Foundation for Statistical Computing, Vienna, Austria. URL http://www.R-project.org/
Reinhardt M, Müller B, Gächter R, Wehrli B (2006) Nitrogen removal in a small constructed wetland: an isotope mass balance approach. Environ Sci Technol 40(10):3313–3319
Shrestha J, Niklaus PA, Frossard E, Samaritani E, Huber B, Barnard RL, Schleppi P, Tockner K, Luster J (2012) Soil nitrogen dynamics in a river floodplain mosaic. J Environ Qual 41(6):2033–2045
Smith CJ, DeLaune RD, Patrick WH (1983) Carbon dioxide emission and carbon accumulation in coastal wetlands. Estuar Coast Shelf Sci 17(1):21–29
Smith KA, Dobbie KE, Ball BC, Bakken LR, Sitaula BK, Hansen S, Brumme R, Borken W, Christensen S, Priemé A (2000) Oxidation of atmospheric methane in Northern European soils, comparison with other ecosystems, and uncertainties in the global terrestrial sink. Glob Change Biol 6(7):791–803
van Groenigen KJ, Osenberg CW, Hungate BA (2011) Increased soil emissions of potent greenhouse gases under increased atmospheric CO2. Nature 475(7355):214–216
VanZomeren CM, White JR, DeLaune RD (2012) Fate of nitrate in vegetated brackish coastal marsh. Soil Sci Soc Am J 76(5):1919–1927
Wang H, Liao G, D’Souza M, Yu X, Yang J, Yang X, Zheng T (2015) Temporal and spatial variations of greenhouse gas fluxes from a tidal mangrove wetland in Southeast China. Environ Sci Pollut Res 23(2):1873–1885
Weston NB, Neubauer SC, Velinsky DJ, Vile MA (2014) Net ecosystem carbon exchange and the greenhouse gas balance of tidal marshes along an estuarine salinity gradient. Biogeochemistry 120(1–3):163–189
Whalen SC (2005) Biogeochemistry of methane exchange between natural wetlands and the atmosphere. Environ Eng Sci 22(1):73–94
White DS, Howes BL (1994) Long-term 15N-nitrogen retention in the vegetated sediments of a New England salt marsh. Limnol Oceanogr 39(8):1878–1892
White JR, Reddy KR (1999) Influence of nitrate and phosphorus loading on denitrifying enzyme activity in Everglades wetland soils. Soil Sci Soc Am J 63(6):1945–1954
Wolf AA, Drake BG, Erickson JE, Megonigal JP (2007) An oxygen-mediated positive feedback between elevated carbon dioxide and soil organic matter decomposition in a simulated anaerobic wetland. Glob Change Biol 13(9):2036–2044
Zhang Y, Ding W, Cai Z, Valerie P, Han F (2010) Response of methane emission to invasion of Spartina alterniflora and exogenous N deposition in the coastal salt marsh. Atmos Environ 44(36):4588–4594
Acknowledgements
The authors thank J. Duls, G. Peresta, and A. Peresta for assistance with data collection and maintenance of the experiment and treatments at the Smithsonian Global Change Research Wetland. We also thank M. Vile for technical insight, as well as two anonymous reviewers for the helpful insights. This work was supported by National Science Foundation-LTREB Program Grants DEB-0950080 and DEB-1457100, the Smithsonian Institution, and Villanova University.
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Pastore, M.A., Megonigal, J.P. & Langley, J.A. Elevated CO2 and nitrogen addition accelerate net carbon gain in a brackish marsh. Biogeochemistry 133, 73–87 (2017). https://doi.org/10.1007/s10533-017-0312-2
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DOI: https://doi.org/10.1007/s10533-017-0312-2


