DISSERTATION RESEARCH: Dynamics of labile organic matter fractions in arctic soils

博士论文研究将确定土壤团聚体（土壤的基础）在多大程度上为北极土壤有机质（SOM）提供稳定。气候变暖与北极地区碳循环的变化有关。低温和缺氧条件抑制微生物活动，减少分解，导致富碳有机物的积累，使本已氮有限的系统变得更加紧张。添加养分改变了植物群落，耗竭了土壤碳；然而，碳损失背后的机制尚不清楚。目前尚不清楚哪些有机质组分在北极土壤中最容易退化，以及2)它们位于土壤基质中的什么位置。这些因素对于理解北极土壤中碳损失背后的机制很重要，这可能部分归因于土壤团聚体物理稳定性的变化。换句话说，大团聚体比例越大的土壤含有更多的碳。在阿拉斯加北坡的北极LTER站点进行的长期营养添加实验中收集了土壤，并将其分为四种大小的团聚体。这些聚集体将被分成子结构元素和自由的OM，这将揭示SOM是否在聚集体中受到保护，哪些部分容易降解。该项目还将把目前土壤碳稳定的概念模型与北极联系起来。研究生将与K-12社区互动，通过现有的研讨会，实习和教师驻校计划为教师提供研究机会。

The proposed doctoral dissertation research will determine the extent to which soil aggregates, a foundation of soils, provide stabilization for soil organic matter (SOM) in the Arctic. Warming has been linked to changes in carbon cycling in the Arctic. Cold temperatures and anoxic conditions inhibit microbial activity and reduce decomposition, resulting in an accumulation of carbon-rich organic matter, straining an already nitrogen-limited system. Nutrient additions have changed the plant community and depleted soil carbon; however, mechanisms behind carbon loss are not understood. It is not known which OM fractions are most susceptible to degradation in Arctic soils, and 2) where are they located within the soil matrix. These factors are important to understanding mechanisms behind carbon loss in Arctic soils, which may be due, in part, to shifts in the physical stability of soil aggregates. In other words, soils with greater proportions of macroaggregates contain more carbon.Soils have been collected from long-term nutrient addition experiments at the Arctic LTER site on the Alaskan North Slope, and were separated into four size classes of aggregates. These aggregates will be separated into sub-structural elements as well as free OM, which will reveal if SOM is protected within aggregates and which fractions are susceptible to degradation. The project will also link current conceptual models of soil carbon stabilization to the Arctic. The graduate student will interact with the K-12 community by providing research opportunities for teachers through existing workshops, internships, and a Teacher-in-Residence program.