Thawing Yedoma permafrost is a neglected nitrous oxide source

M E Marushchak,K Diáková,C Knoblauch,J Gil,A Faguet,M Nykamb,H M P Siljanen,C Biasi,J G Ronkainen,N Zimov,C Voigt,N Lashchinskiy,S Zimov,A Morgenstern,P J Martikainen,G Grosse,J Kerttula,L Van Delden

doi:10.1038/s41467-021-27386-2

Abstract

In contrast to the well-recognized permafrost carbon (C) feedback to climate change, the fate of permafrost nitrogen (N) after thaw is poorly understood. According to mounting evidence, part of the N liberated from permafrost may be released to the atmosphere as the strong greenhouse gas (GHG) nitrous oxide (N2O). Here, we report post-thaw N2O release from late Pleistocene permafrost deposits called Yedoma, which store a substantial part of permafrost C and N and are highly vulnerable to thaw. While freshly thawed, unvegetated Yedoma in disturbed areas emit little N2O, emissions increase within few years after stabilization, drying and revegetation with grasses to high rates (548 (133–6286) μg N m−2 day−1; median with (range)), exceeding by 1–2 orders of magnitude the typical rates from permafrost-affected soils. Using targeted metagenomics of key N cycling genes, we link the increase in in situ N2O emissions with structural changes of the microbial community responsible for N cycling. Our results highlight the importance of extra N availability from thawing Yedoma permafrost, causing a positive climate feedback from the Arctic in the form of N2O emissions.

Highlights

In contrast to the well-recognized permafrost carbon (C) feedback to climate change, the fate of permafrost nitrogen (N) after thaw is poorly understood
While it is long known that mobilization of permafrost C potentially increase the release of the greenhouse gases (GHG) carbon dioxide (CO2) and methane (CH4)[5,9,10], the fate of soil N liberated upon permafrost thaw is poorly studied and more complex
Tropical soils with high N turnover rates generally show the largest N2O emissions among natural soils, while permafrost-affected soils in cold environments have been thought to be negligible N2O sources. This view was challenged by a recent synthesis showing that N2O emissions commonly occur from permafrost soils, with a global emission between 0.08 and 1.27 Tg N year−1, meaning a 1–23% addition to the global N2O emission from natural soils[6]

Summary

Introduction

In contrast to the well-recognized permafrost carbon (C) feedback to climate change, the fate of permafrost nitrogen (N) after thaw is poorly understood. The spatial pattern in the N2O emissions in situ was confirmed by laboratory incubations with Kurungnakh soils, where the highest N2O production under anoxic conditions was found in Yedoma revegetated with grasses and the lowest in bare earlier thawed Yedoma and vegetated Holocene cover (Kruskall–Wallis test, p = 0.0004–0.007; Fig. 3a, Supplementary Table 4).

Results

Conclusion