How is nitrogen fixation in the high arctic linked to greenhouse gas emissions?
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Background and aims
Approximately 50 % of belowground organic carbon is present in the northern permafrost region and due to changes in climate there are concerns that this carbon will be rapidly released to the atmosphere. The release of carbon in arctic soils is thought to be intimately linked to the N cycle through the N cycle’s influence on microbial activity. The majority of new N input into arctic systems occurs through N2-fixation; therefore, N2-fixation may be the key driver of greenhouse gases from these ecosystems.
At Alexandra Fjord lowland, Ellesmere Island, Canada concurrent measurements of N2-fixation, N mineralization and nitrification rates, dissolved organic soil N (DON) and C, inorganic soil N and surface greenhouse gas fluxes (CO2, N2O and CH4) were taken in two ecosystem types (Wet Sedge Meadow and Dryas Heath) over the 2009 growing season (June-August). Using Structural Equation Modelling we evaluated the hypothesis that CO2, CH4 and N2O flux are linked to N2-fixation via the N cycle.
The soil N cycle was linked to CO2 flux in the Dryas Heath ecosystem via DON concentrations, but there was no link between the soil N cycle and CO2 flux in the Wet Sedge Meadow. Methane flux was also not linked to the soil N cycle, nor surface soil temperature or moisture in either ecosystem. The soil N cycle was closely linked to N2O emissions but via nitrification in the Wet Sedge Meadow and inorganic N in the Dryas Heath, indicating the important role of nitrification in net N2O flux from arctic ecosystems.
Our results should be interpreted with caution given the high variability in both the rates of the N cycling processes and greenhouse gas flux found in both ecosystems over the growing season. However, while N2-fixation and other N cycling processes may play a more limited role in instantaneous CO2 emissions, these processes clearly play an important role in controlling N2O emissions.
KeywordsN2-fixation N cycle N mineralization Nitrification Soil moisture Carbon dioxide Nitrous oxide Methane
This work was funded by a NSERC Discovery to SDS, NSERC Northern Supplement to SDS, IPY CiCAT to SDS and DSC, NSTP to KJS and PCSP logistical support provided to SDS. GHR Henry’s facilitation of the Alexandra Fjord Long Term Ecological Research Station is gratefully acknowledged. Statistical advice from EG Lamb is acknowledged.
- Brummell ME, Siciliano SD (2011) Measurement of carbon dioxide, methane, nitrous oxide, and water potential in soil ecosystems. In: Klotz MG, Stein LY (eds) Methods in enzymology. Academic, Burlington, pp 115–137Google Scholar
- Chapin DM (1996) Nitrogen mineralization, nitrification, and denitrification in a high Arctic lowland ecosystem, Devon, Island, N.W.T., Canada. Arct Antarct Alp Res 28:85–92Google Scholar
- Chapin DM, Bledsoe C (1992) Nitrogen fixation in arctic plant communities. In: Chapin FS III, Jefferies RL, Reynolds JF, Shaver GR, Svoboda J (eds) Arctic ecosystems in a changing climate: an ecophysiological perspective. Academic, San Diego, pp 301–319Google Scholar
- Christensen TR, Jonasson S, Callaghan TV, Havstrom M, Livens FR (1999) Carbon cycling and methane exchange in Eurasian tundra ecosystems. Ambio 28:239–244Google Scholar
- Drewer J, Lohila A, Aurela M, Tl L, Minkkinen K, Penttila T, Dinsmore KJ, McKenzie TM, Helfter C, Flechard C, Sutton MA, Skiba UM (2010) Comparison of greenhouse gas fluxes and nitrogen budgets from an ombotrophic bog in Scotland and a minerotrophic sedge fen in Finland. Europ J Soil Sci 61:640–650CrossRefGoogle Scholar
- Hart SC, Stark JM, Davidson, EA, Firestone MK (1994) Nitrogen mineralization, immobilization, and nitrification. In: Methods of Soil Analysis, Part 2 - Microbiological and Biochemical Properties. SSSA Book Series, no. 5, Madison, WI, pp 985–1018Google Scholar
- Henry GHR, Svoboda J (1986) Dinitrogen fixation (acetylene reduction) in high arctic sedge meadow communities. Arct Antarct Alp Res 18:181–187Google Scholar
- Hobbie SE, Chapin FS III (1998) The response of tundra plant biomass, aboveground production, nitrogen and flux to experimental warming. Ecol 79:1526–1544Google Scholar
- Johnson LC, Shaver GR, Cades DH, Rastetter E, Nadelhoffer K, Giblin A, Laundre J, Stanley A (2000) Plant carbon-nutrient interactions control CO2 exchange in Alaskan wet sedge tundra ecosystems. Ecol 81:453–469Google Scholar
- Labine C (1994) Meterology and climatology of the Alexandra Fiord Lowland. In: Svoboda J, Freedman B (eds) Ecology of a Polar Oasis: Alexandra Fiord Ellesmere Island Canada. Captus University Publications, Toronto, pp 23–40Google Scholar
- Muc M, Freedman B, Svoboda J (1989) Vascular plant communities of a polar oasis at Alexandra Fiord (79oN), Ellesmere Island, Canada. Can J Bot 6:1126–1136Google Scholar
- Muc M, Svoboda J, Freedman B (1994) Soils of an extensively vegetated polar desert oasis, Alexandra Fiord, Ellesmere Island. In: Svoboda J, Freedman B (eds) Ecology of a Polar Oasis: Alexandra Fiord Ellesmere Island Canada. Captus University Publications, Toronto, pp 41–50Google Scholar
- Nadelhoffer KJ, Giblin AE, Shaver GR, Linkins AE (1992) Microbial processes and plant nutrient availability in arctic soils. In: Chapin FS III, Jefferies RL, Reynolds JF, Shaver GR, Svoboda J (eds) Arctic ecosystems in a changing climate: an ecophysiological perspective. Academic, San Diego, pp 281–300Google Scholar
- Norton JM, Stark JM (2011) Regulation and measurement of nitrification in terrestrial systems. In: Klotz MG, Stein LY (eds) Methods in enzymology. Academic, Burlington, pp 343–368Google Scholar
- Paul EA, Clark FE (1996) Soil microbiology and biochemistry. Academic, TorontoGoogle Scholar
- Rolph SG (2003) Effects of a ten-year climate warming experiment on nitrogen cycling in the high arctic tundra. MSc Thesis, University of British Columbia, CanadaGoogle Scholar
- Shaver GR, Nadelhoffer KJ, Giblin AE (1990) Biogeochemical diversity and element transport in a heterogeneous landscape, the North Slope of Alaska. In: Turner M, Gardner R (eds) Quantitative methods in landscape ecology. Springer, New York, pp 105–125Google Scholar
- Shaver GR, Johnson LC, Cades DH, Murray G, Laundre JA, Rastetter EB, Nadelhoffer KJ, Giblin AE (1998) Biomass and CO2 flux in wet sedge tundras: responses to nutrients, temperature and light. Ecol Monogr 68:75–97Google Scholar
- Soil Classification Working Group (1998) The Canadian System of Soil Classification. 3rd ed. Agric. Agri-Food Can. Publ. 1646 Ottawa, 187ppGoogle Scholar
- Van Wijk MT, Clemmensen KE, Shaver GR, Williams M, Callaghan TV, Chapin FS III, Cornelissen JHC, Gough L, Hobbie SE, Jonasson S, Lee JA, Michelsen A, Press MC, Richardson SJ, Rueth H (2003) Long-term ecosystem level experiments at Toolik Lake, Alaska, and at Abisko, Northern Sweden: generalizations and differences in ecosystem and plant type response to global change. Glob Chang Biol 10:105–123CrossRefGoogle Scholar