Journal cover Journal topic
Biogeosciences An interactive open-access journal of the European Geosciences Union
Journal topic
Volume 14, issue 10
Biogeosciences, 14, 2611–2626, 2017
https://doi.org/10.5194/bg-14-2611-2017
© Author(s) 2017. This work is distributed under
the Creative Commons Attribution 3.0 License.
Biogeosciences, 14, 2611–2626, 2017
https://doi.org/10.5194/bg-14-2611-2017
© Author(s) 2017. This work is distributed under
the Creative Commons Attribution 3.0 License.

Research article 23 May 2017

Research article | 23 May 2017

Flooding-related increases in CO2 and N2O emissions from a temperate coastal grassland ecosystem

Amanuel W. Gebremichael1,2,3, Bruce Osborne2,3, and Patrick Orr1,3 Amanuel W. Gebremichael et al.
  • 1UCD School of Earth Sciences, University College Dublin, Belfield, Dublin 4, Ireland
  • 2UCD School of Biology and Environmental Sciences, University College Dublin, Belfield, Dublin 4, Ireland
  • 3UCD Earth Institute, University College Dublin, Belfield, Dublin 4, Ireland

Abstract. Given their increasing trend in Europe, an understanding of the role that flooding events play in carbon (C) and nitrogen (N) cycling and greenhouse gas (GHG) emissions will be important for improved assessments of local and regional GHG budgets. This study presents the results of an analysis of the CO2 and N2O fluxes from a coastal grassland ecosystem affected by episodic flooding that was of either a relatively short (SFS) or long (LFS) duration. Compared to the SFS, the annual CO2 and N2O emissions were 1.4 and 1.3 times higher at the LFS, respectively. Mean CO2 emissions during the period of standing water were 144 ± 18.18 and 111 ± 9.51 mg CO2–C m−2 h−1, respectively, for the LFS and SFS sites. During the growing season, when there was no standing water, the CO2 emissions were significantly larger from the LFS (244 ± 24.88 mg CO2–C m−2 h−1) than the SFS (183 ± 14.90 mg CO2–C m−2 h−1). Fluxes of N2O ranged from −0.37 to 0.65 mg N2O–N m−2 h−1 at the LFS and from −0.50 to 0.55 mg N2O–N m−2 h−1 at the SFS, with the larger emissions associated with the presence of standing water at the LFS but during the growing season at the SFS. Overall, soil temperature and moisture were identified as the main drivers of the seasonal changes in CO2 fluxes, but neither adequately explained the variations in N2O fluxes. Analysis of total C, N, microbial biomass and Q10 values indicated that the higher CO2 emissions from the LFS were linked to the flooding-associated influx of nutrients and alterations in soil microbial populations. These results demonstrate that annual CO2 and N2O emissions can be higher in longer-term flooded sites that receive significant amounts of nutrients, although this may depend on the restriction of diffusional limitations due to the presence of standing water to periods of the year when the potential for gaseous emissions are low.

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