The Bugs of Winter: Microbial Control of Soil Biogeochemistry During the Arctic Cold Season

真实的北极年主要是9个月的“寒冷季节”，其中包括活动层处于最大深度的时期和土壤冻结并保持在0摄氏度的延长时期。 冷季CO2通量是年度碳收支的重要组成部分，冷季氮矿化似乎主导年度氮矿化。 在生长季节和寒冷季节之间发生的微生物过程有重大转变，它们似乎发生在0 ℃以上。 冷季过程不同于生长季过程。 然而，我们对冷季土壤过程的了解还不足以将其纳入北极生态系统功能模型。 已提供资金分析北极寒冷季节条件下土壤中基质使用模式的变化。 具体而言，PI建议：1。评价各主要土层中“冬不稳定”基质库的大小，2.评估在解冻和低温条件下使用的特定底物，和3.评估不同工艺调节底物使用的相对重要性。 这些可能包括物理学（温度曲线），物理化学（柠檬酸-温度响应关系），生物物理学（微生物与未冻结水膜的相互作用），生物化学（细胞外酶活性随温度的变化）和生物学（改变微生物群落和生理能力）。这项研究将包括从不同的土壤层（有机，矿物）耦合到池和控制因素的实验室分析CO2通量的实地测量。 长期实验室生物测定将用于评估“冬季不稳定”池的大小，13 C示踪剂研究将用于评估特定底物的处理（单体和聚合物）以及它们如何随温度变化，酶势测定以评估随温度变化的酶动力学，NMR以测量未冻结水曲线，电子显微镜以评估微生物如何（细菌和真菌）与水膜的相互作用，13 C磷脂脂肪酸分析以评估进入微生物群落不同组分的碳流，以及DNA和RNA指纹分析以评估微生物群落在生长季节和寒冷季节之间是否以及如何变化。

The real Arctic year is dominated by the 9 month long "cold season", which includes the period when the active layer is at its maximum depth and an extended period while soils are freezing and held at 0 degrees C. Cold-season CO2 fluxes are a substantial component of the annual carbon budget and cold-season nitrogen mineralization appears to dominate annual nitrogen mineralization. There are major shifts in microbial processes that occur between the growing and cold seasons, and they appear to occur above 0 degrees C. Cold-season processes are different from growing season processes. However, we don't understand cold season soil processes sufficiently to incorporate them into models of Arctic ecosystem functioning. Funds have been provided to analyze changing substrate use patterns in soils under Arctic cold season conditions. Specifically, the PI proposes: 1. to evaluate the size of the "winter-labile" substrate pool in each major soil layer, 2. to evaluate specific substrates that are used under thawed and cold conditions, and3. to evaluate the relative importance of the different processes regulating substrate use. These likely include physics (temperature profiles), physical chemistry (recalcitrance-temperature responsiveness relationships), biophysics (microbial interactions with unfrozen water films), biochemistry (shifts in extracellular enzyme activities with temperature), and biology (changing microbial communities and physiological capacities). This research will include field measurements of CO2 flux from different soil horizons (organic, mineral) coupled to laboratory analysis of pools and controlling factors. Long-term lab bioassays will be used to evaluate the size of the "winter-labile" pool, 13C tracer studies to evaluate the processing of specific substrates (monomers and polymers) and how they change with temperature, enzyme potential assays to evaluate changing enzyme kinetics with temperature, NMR to measure unfrozen water curves and electron microscopy to evaluate how microbes (bacteria and fungi) interact with water films, 13C phospholipid fatty acid analyses to evaluate carbon flow into different components of the microbial community, and DNA and RNA fingerprinting to evaluate whether and how microbial communities change between the growing and cold seasons.