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

北极地区包括中国北方地区的多年冻土储存了大量的土壤有机碳和氮。在气候变暖的情况下，这些股票有可能变成矿物和挥发。虽然在气候变暖的情况下，融化的永久冻土中的碳以二氧化碳和甲烷的形式转化和释放已经得到了深入的研究，但对氮的释放知之甚少，氮的释放可能部分以强效温室气体一氧化二氮的形式发生。因此，NIFROCLIM旨在量化北方亚洲典型多年冻土景观的土壤N2 O排放量，跨越典型景观特征的梯度，包括不同方面的低地泥炭地和森林高地土壤。我们假设，随着气候变暖，活性层的厚度增加，更多的土壤氮变得有效，这是部分损失的气态氮。为了预测N2 O排放的主持下，气候变暖，它的目标是实现一个面向过程的理解土壤N2 O的形成和消耗不同的冻土土壤类型，并在垂直土壤剖面，包括解冻前的活动层。为此，我们提出a）在中国北方景观样带的土壤-大气界面和野外变暖实验中测量温室气体通量，这与B）土壤地球化学过程研究相联系，以量化潜在的N循环过程，和c）分子方法来表征和量化结构，参与氮循环的土壤微生物组的多样性和活性，以及d）土壤有机质的物理和光谱特性。这些实地研究由受控条件下的有针对性的实验室实验补充，其中活动层的深度，地下水位和温度都受到控制。总的来说，我们希望实现一个功能性的了解，氮周转过程中涉及的生产和消费的N2 O在典型的多年冻土层土壤的影响，活跃层的高度。因此，我们将提供迫切需要的信息，以限制在不断变化的气候条件下，从永冻土土壤的N2 O排放量的估计。

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.