EGU2020-5432
https://doi.org/10.5194/egusphere-egu2020-5432
EGU General Assembly 2020
© Author(s) 2020. This work is distributed under
the Creative Commons Attribution 4.0 License.

The Nitrogen Dynamics of Multi-species Grasslands when Subject to Drought and Re-wetting.

Saoirse Cummins1, John Finn1, Gary Lanigan1, Karl Richards1, Tom Misselbrook2, Laura Cardenas2, Chris Reynolds3, and Dominika Krol1
Saoirse Cummins et al.
  • 1Teagasc, CELUP crops environment and land use, Co. Wexford, Ireland
  • 2Rothamsted Research, North Wyke, Okehampton, Devon, EX20 2SB, UK
  • 3University of Reading, School of Agriculture, Earley, Reading RG6 6BZ, UK

It is predicted that climate change will result in more extreme and frequent weather events including flooding and drought. Nitrous oxide (N2O) is a potent greenhouse gas having 298 times the global warming potential of CO2. The ‘Birch effect’, the term given to high  N2O fluxes following the drying and re-wetting of soils, is an accelerator of this process. Multi species grasslands have been shown have higher nitrogen use efficiency and potential for drought resilience and recovery. This experiment analysed the nitrogen dynamics of multi-species grasslands by means of quantifying the responses of soil mineral nitrogen (NH4+ and NO3-) and N2O fluxes during an eight week simulated drought, re-wetting and fertiliser application two weeks after the re-wetting event. A simplex experimental design was used to determine species and functional group effects which could potentially influence responses. The hypothesis of this study was therefore that multi species grasslands would mitigate the ‘Birch effect’ resulting in less erratic transformations of soil mineral nitrogen and lower N2O fluxes compared to monocultures. This study also predicted a lasting legacy effect of drought on soil systems resulting in prolonged heightened N2O fluxes. Drought resulted in a depletion of soil NO3-, increased  levels of NH4+ and background level N2O emissions. Following re-wetting soil mineral N underwent transformations from NH4+ to NO3- indicating nitrification. Four times more N2O emissions were recorded during re-wetting period compared to fertilizer application. There was no lasting legacy effect of drought and re-wetting on N2O fluxes observed during fertilizer application two weeks after re-wetting bar T. repens which has implications for grassland management strategies.

How to cite: Cummins, S., Finn, J., Lanigan, G., Richards, K., Misselbrook, T., Cardenas, L., Reynolds, C., and Krol, D.: The Nitrogen Dynamics of Multi-species Grasslands when Subject to Drought and Re-wetting., EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-5432, https://doi.org/10.5194/egusphere-egu2020-5432, 2020

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