Eight Mile Lake Research Watershed, Thaw Gradient: Geochemical data from perched waters collected from boreholes on Gradient site during August-September 2019

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. Geochemical analysis of water perched on the permafrost table complements the overarching aim of this study by targeting the organic component transported laterally from the soils. The association between DOC and mineral elements in the waters perched on the permafrost table was determined. These mineral element-organic carbon associations must be accounted for when considering the stability of organic carbon transported laterally from the catchment.

在本项大型研究中，我们旨在解答如下科学问题：占土壤有机质（soil organic matter, SOM）库主体的老旧碳，是否会因永久冻土融化而被释放？本研究通过结合野外与室内实验，测量苔原生态系统中土壤有机质、土壤呼吸及溶解性有机碳（dissolved organic carbon, DOC）的放射性碳同位素比值，以此解答上述问题。本次测定工作的核心目标是从机制层面阐明永久冻土融化后，参与碳流失的土壤有机质来源。我们将在阿拉斯加山脉山麓、阿拉斯加州希利（Healy）附近一处已建成的苔原野外站点开展上述测定。野外实验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并发生融化。该区域包含一系列梯度样地，各样地因永久冻土融化所经历的环境变化程度各不相同。正因如此，该区域具备独特优势，可用于研究与北极生态系统变化相关的时间与空间尺度下的科学问题。针对永久冻土层之上的滞水开展地球化学分析，聚焦土壤侧向输运的有机组分，以此补充本研究的整体研究目标。本研究测定了永久冻土层之上滞水中DOC与矿物元素之间的关联特征。在评估流域侧向输运有机碳的稳定性时，必须考量上述矿物元素-有机碳的关联特征。