Eight Mile Lake Research Watershed, Thaw Gradient, Ecosystem carbon balance: Eddy covariance CO2 flux data of a heterogenous landscape undergoing permafrost thaw.

In this larger study, we are asking the question: Is old carbon that comprises the bulk of the soil organic matter pool released in response to thawing of permafrost? We are answering this question by using a combination of field and laboratory experiments to measure radiocarbon isotope ratios in soil organic matter, soil respiration, and dissolved organic carbon, in tundra ecosystems. The objective of these proposed measurements is to develop a mechanistic understanding of the SOM sources contributing to C losses following permafrost thawing. We are making these measurements at an established tundra field site near Healy, Alaska in the foothills of the Alaska Range. Field measurements center on a natural experiment where permafrost has been observed to warm and thaw over the past several decades. This area represents a gradient of sites each with a different degree of change due to permafrost thawing. As such, this area is unique for addressing questions at the time and spatial scales relevant for change in arctic ecosystems. Understanding how landscape level physical and biological changes effect carbon cycling is important for estimating the carbon balance of an ecosystem undergoing permafrost thaw.

在本大型研究中，我们聚焦核心研究问题：占土壤有机质（Soil Organic Matter, SOM）库主体的老旧碳，是否会因永久冻土解冻而被释放？我们将结合野外实验与室内实验，对苔原生态系统中土壤有机质、土壤呼吸作用及溶解性有机碳的放射性碳同位素比值开展测定，以此解答该问题。本次拟定测量工作的目标，是对永久冻土解冻后驱动碳损失的土壤有机质来源形成机制性认知。我们将在阿拉斯加山脉山麓地带、阿拉斯加州希利镇附近一处已建成的苔原野外监测点开展上述测量。野外测量以一项天然观测实验为核心：该区域内永久冻土在过去数十年间持续增温和解冻。该区域涵盖了一系列因永久冻土解冻程度不同而呈现出差异化变化的监测样地，具备独特优势，可在与北极生态系统变化相关的时间与空间尺度下开展相关问题研究。明晰景观尺度的物理与生物变化如何影响碳循环，对估算正经历永久冻土解冻的生态系统的碳平衡具有重要意义。