Chronic atmospheric reactive nitrogen deposition suppresses biological nitrogen fixation in peatlands

Research output: Contribution to journalArticlepeer-review


  • Ernesto Saiz
  • Fotis Sgouridis
  • Falko Drifjhout
  • Matthias Peichl
  • Mats Nilsson

Colleges, School and Institutes

External organisations

  • Keele University
  • University of Bristol
  • Swedish University of Agricultural Sciences


Biological nitrogen fixation (BNF) represents the natural pathway by which mosses meet their demands for bioavailable/reactive nitrogen (Nr) in peatlands. However, following intensification of nitrogen fertilizer and fossil fuel use, atmospheric Nr deposition has increased exposing peatlands to Nr loading often above the ecological threshold. As BNF is energy intensive, therefore, it is unclear whether BNF shuts down when Nr availability is no longer a rarity. We studied the response of BNF under a gradient of Nr deposition extending over decades in three peatlands in the UK, and at a background deposition peatland in Sweden. Experimental nitrogen fertilization plots in the Swedish site were also evaluated for BNF activity. In situ BNF activity of peatlands receiving Nr deposition of 6, 17 and 27 kg N ha-1 yr-1 was not shut down but rather suppressed by 54, 69 and 74%, respectively, compared to the rates under background Nr deposition of ~2 kg N ha-1 yr-1. These findings were corroborated by similar BNF suppression at the fertilization plots in Sweden. Therefore, contribution of BNF in peatlands exposed to chronic Nr deposition needs accounting when modelling peatland’s nitrogen pools, given that nitrogen availability exerts a key control on the carbon capture of peatlands, globally.


Original languageEnglish
JournalEnvironmental Science and Technology
Early online date4 Jan 2021
Publication statusE-pub ahead of print - 4 Jan 2021