CryoN - Mechanisms underlying large N2O emissions from cryoturbated peat surfaces in tundra

Principal investigator: Assoc. Prof. Christina Biasi

Funding duration: 2009-2014 (Academy of Finland; decision Nr. 132045)

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? By using stable isotope and molecule approaches the best-possible tool for answering the key questions related to the hotspots emissions found in the Arctic are provided. The studies are novel and have not been yet implemented in the Arctic before. 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.

The project includes specialists in Arctic ecology and enjoys the benefits of cooperation with high-level international experts governing all the key methodological know-how needed. We currently know very little about the tundra as a source of atmospheric N2O, despite its significance in terms of natural land cover, and so this project will provide major advances in our ability to constrain the global N2O budget, as well as in furthering understanding of the regulators of N2O production.