Synthesizing greenhouse gas fluxes across nine European peatlands and shrublands – responses to climatic and environmental changes

• Published in: Biogeosciences
• Main Authors: Carter, M. S., Larsen, K. S., Emmett, B., Estiarte, M., Field, C., Leith, I. D., Lund, M., Meijide, A., Mills, R. T. E., Niinemets, Ü., Peñuelas, J., Portillo-Estrada, M., Schmidt, I. K., Selsted, M. B., Sheppard, L. J., Sowerby, A., Tietema, A., Beier, C.
• Format: Text
• Language: English
• Published: 2018
• Subjects: Northern Sweden
• Online Access: https://doi.org/10.5194/bg-9-3739-2012; https://www.biogeosciences.net/9/3739/2012/

In this study, we compare annual fluxes of methane (CH 4 ), nitrous oxide (N 2 O) and soil respiratory carbon dioxide (CO 2 ) measured at nine European peatlands ( n = 4) and shrublands ( n = 5). The sites range from northern Sweden to Spain, covering a span in mean annual air temperature from 0 to 16 °C, and in annual precipitation from 300 to 1300 mm yr −1 . The effects of climate change, including temperature increase and prolonged drought, were tested at five shrubland sites. At one peatland site, the long-term (> 30 yr) effect of drainage was assessed, while increased nitrogen deposition was investigated at three peatland sites. The shrublands were generally sinks for atmospheric CH 4 , whereas the peatlands were CH 4 sources, with fluxes ranging from −519 to +6890 mg CH 4 -C m −2 yr −1 across the studied ecosystems. At the peatland sites, annual CH 4 emission increased with mean annual air temperature, while a negative relationship was found between net CH 4 uptake and the soil carbon stock at the shrubland sites. Annual N 2 O fluxes were generally small ranging from −14 to 42 mg N 2 O-N m −2 yr −1 . Highest N 2 O emission occurred at the sites that had highest nitrate (NO 3 − ) concentration in the soil water. Furthermore, experimentally increased NO 3 − deposition led to increased N 2 O efflux, whereas prolonged drought and long-term drainage reduced the N 2 O efflux. Soil CO 2 emissions in control plots ranged from 310 to 732 g CO 2 -C m −2 yr −1 . Drought and long-term drainage generally reduced the soil CO 2 efflux, except at a hydric shrubland where drought tended to increase soil respiration. In terms of fractional importance of each greenhouse gas to the total numerical global warming response, the change in CO 2 efflux dominated the response in all treatments (ranging 71–96%), except for NO 3 − addition where 89% was due to change in CH 4 emissions. Thus, in European peatlands and shrublands the effect on global warming induced by the investigated anthropogenic disturbances will be dominated by variations in soil CO 2 fluxes.