Soil nitrogen turnover and nitrous oxide emissions in continuous permafrost landscapes of Northern China in a changing climate (NIFROCLIM)

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Permafrost soils of the Arctic regions including those situated in Northern China store vast amounts of soil organic carbon and nitrogen. These stocks are at risk to become mineralized and volatilized in a warming climate. While turnover and release of carbon from thawing permafrost soils in a warming climate in form of carbon dioxide and methane have been intensively investigated, much less is known on nitrogen release, which is likely to occur partially in the form of the potent greenhouse gas nitrous oxide. NIFROCLIM therefore aims at the quantification of soil N2O emissions from typical Permafrost landscapes in Northern Asia, spanning gradients across typical landscape features and including lowland peatland and forested upland soils of different aspect. We hypothesize that with climate warming the thickness of the active layer increases and more soil N becomes available which is partly lost as gaseous N. In order to predict N2O emissions under the auspices of climate warming, it is the goal to achieve a process-oriented understanding of soil N2O formation and consumption across different permafrost soil types, and across vertical soil profiles including the thawing front of the active layer. For this purpose, we propose a) greenhouse gas flux measurements at the soil-atmosphere interface of landscape transects and in field warming experiments in Northern China, which are linked with b) biogeochemical process studies to quantify the underlying N cycling processes, and c) molecular approaches to characterize and quantify the structure, diversity and activity of the soil microbiome involved in N cycling as well as d) physical and spectroscopic characterization of soil organic matter. These field studies are e) complemented by targeted laboratory experiments under controlled conditions, where the depth of the active layer, the water table and temperatures are manipulated. Overall we expect to achieve a functional understanding of nitrogen turnover processes involved in production and consumption of N2O in typical permafrost soils as affected by active layer height. Thus, we will provide urgently needed information to constrain estimates of N2O emissions from permafrost soils in a changing climate.