1 Nitrogen accumulation and partitioning in High Arctic tundra ecosystem 2 from extreme atmospheric N deposition events 3 4 Sonal Choudhary1,2*, Aimeric Blaud1, A. Mark Osborn1,3, Malcolm C. Press4, Gareth K. 5 Phoenix1 6 7 1Department of Animal and Plant Sciences, University of Sheffield, Western Bank, Sheffield, 8 S10 2TN, UK 9 2Management School, University of Sheffield, Conduit Road, Sheffield, S10 1FL, UK 10 3School of Applied Sciences, RMIT University, PO Box 71, Bundoora, VIC 3083, Australia 11 4School of Biosciences, University of Birmingham, Edgbaston, Birmingham, B15 2TT, UK 12 Corresponding author: 13 Sonal Choudhary 14 e:
[email protected], t: +44 (0)114 222 3287; f: +44 (0)114 222 3348 15 16 Running Headline: Extreme N deposition event fate in High Arctic Tundra 17 18 19 20 21 22 23 24 25 26 1 27 Graphical abstract 28 29 30 Highlights 31 • High Arctic tundra demonstrated a very high (90–95%) N pollutant retention capacity. 32 • Non-vascular plants and soil microbial biomass were important short-term N sinks. 33 • Vascular plants and soil showed capacity to be efficient longer-term N sinks. 34 • Deposition rich in nitrate can alter almost all ecosystem N pools. 35 • Extreme N depositions may already be contributing to the N enrichment of tundra. 36 37 38 Abstract 39 Arctic ecosystems are threatened by pollution from recently detected extreme 40 atmospheric nitrogen (N) deposition events in which up to 90% of the annual N deposition 41 can occur in just a few days. We undertook the first assessment of the fate of N from extreme 42 deposition in High Arctic tundra and are presenting the results from the whole ecosystem 15N 43 labelling experiment.