AP: CryoN – Mechanisms underlying large N2O emissions from cryoturbated peat surfaces in tundra

People: Pertti Martikainen (PI), Christina Biasi (co-PI)

Background

Nitrous oxide (N2O) is a strong greenhouse gas responsible for global warming. The soil contributes with about 70% to the global annual emissions of N2O, with tropical and agricultural soils accounting for the largest part. Previously, it was believed that tundra soils are negligible within the global N2O budget due to the nitrogen limited nature of this ecosystem. It was thus surprising, when we recently discovered exceptionally large N2O hotspots in tundra. The emissions derive from patches of bare peat, known as peat circles which develop through cryoturbation, and are among the highest found from any other soil. After identifying thitherto unknown N2O sources in tundra, the major questions concern the mechanisms of the large emissions, which are yet unknown. The purpose of this project is thus to explicitly address the mechanisms underlying the high N2O emissions from cryoturbated surfaces in tundra in order to evaluate their atmospheric significance. We propose to answer four major questions related to N2O hotspots in tundra: 1) Which microbial/chemical processes contribute to the N2O production in the peat circles? 2) Which are the key environmental factors controlling the high N2O emissions from the peat circles? 3) Does the microbial community structure, specifically the nitrifier community structure, control the N2O emissions? 4) What is the spatial variability of N2O hotspots in tundra? The work focuses on nitrogen cycling processes, but investigates also several interconnected aspects of carbon dynamics in tundra. In this context, it is linked to CryoCARB, a research project within ERA NET scheme EuroPOLAR.

Fig. 1: Quickbird satellite image (Google Earth) of Tundra landscape in northern Russia (Komi Republic). The brown patches clearly visible in the image are peat cycles.

Fig. 2: Closer view on peat circles. Characteristic diameter of one peat circle is about 20 m (Picture taken by T. Virtanen).
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Fig. 3: Thermokarst, where the surface collapses after underground ice melts
(Picture taken by M. Repo)
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Collaborations

Dr. Liz Baggs (University of Aberdeen), Prof. Andreas Richter (University of Vienna), Prof. Christa Schleper  (University of Bergen) and CryoCARB consortium

The project is funded by Academy of Finland (2010-2013; decision Nr. 132045)

For more information contact Christina.Biasi@uef.fi

References

Repo M.E., Susiluoto S., Lind S.E., Jokinen S., Elsakov V., Biasi C., Virtanen T. & Martikainen P.J. (2009) Large N2O emissions from cryoturbated peat soil in tundra.  Nature Geoscience 2, 189 – 192.