Unfrozen water availability controls microbial temperature dependence of CO2 production in frozen soils

未冻水的可用性控制冻土中二氧化碳产生的微生物温度依赖性

• 批准号: RGPIN-2022-03334
• 负责人: Rezanezhad, Fereidoun
• 金额: $ 2.62万
• 依托单位: University of Waterloo
• 依托单位国家: 加拿大
• 项目类别: Discovery Grants Program - Individual
• 财政年份: 2022
• 资助国家: 加拿大
• 起止时间: 2022-01-01 至 2023-12-31
• 项目状态: 已结题
• 来源: https://www.nserc-crsng.gc.ca/ase-oro/Details-Detailles_eng.asp?id=750859
• 关键词: Unfrozen; water; availability; controls; microbial

High latitude cold regions are warming more than twice as fast as the rest of the planet, with the greatest warming occurring during the winter. Given that a major process responsible for carbon dioxide (CO2) emissions and microbial respiration, increases with warming even at sub-zero temperatures, the CO2 emissions during the non-growing season (NGS; fall, winter, spring) are expected to increase as the climate warms. In addition to the temperature-dependence of microbial metabolic activity, soil organic matter decomposition during the NGS can also be inhibited by soil freezing, which limits the supply of molecular oxygen (O2) and the availability of unfrozen liquid water. Therefore, a comprehensive understanding of partitioning between a temperature response and the effect of unfrozen water availability on soil CO2 production at low temperatures is essential not only for predicting the fate of the vulnerable carbon stocks in northern terrestrial ecosystems, but for accurate predictions of carbon balances and creating climate adaptation and mitigation strategies. The proposed Discovery Grant program seeks to fill a fundamental gap in our understanding of temperature dependence of CO2 production in frozen soils and the transient response of soil biogeochemistry to winter climate warming. The proposed approach combines the detailed measurements of gas-phase and aqueous phase chemistry, to quantify the rates of soil microbial respiration during freeze-thaw cycles, as well as the changes in microbial community structure and the interactive effects of temperature and unfrozen water content on microbially-mediated soil CO2 efflux. The laboratory experiments are designed to assess soil hydrophysical parameters and biogeochemical rates and fluxes that regulate major microbial metabolic processes. The experimental results will improve the fundamental process-based understanding of winter soil biogeochemical processes and will be integrated in the reactive transport and bioenergetics modelling to simulate the biogeochemical transformations of carbon and nutrients and microbial reaction networks under variable winter warming scenarios. This will be a significant step forward in long-term objective of my Discovery Grant program to create the foundation for predictively simulate reaction dynamics in cold regions' subsurface environments, by identifying the dominant biogeochemical drivers of winter soil geomicrobial activity under current and future climate change scenarios. The outcomes of this Discovery Grant research will be a valuable knowledge translation tool in facilitating the percolation of scientific data and knowledge on the climate-sensitivity of carbon dynamics in northern ecosystems and in developing robust climate change adaptation strategies. The proposed research will provide students with innovative and enhanced training and a competitive edge to pursue careers in earth and environmental sciences in academic, government or private sectors.

高纬度地区的变暖速度是地球其余部分的两倍以上，冬季发生的变暖最大。鉴于导致二氧化碳（CO2）排放和微生物呼吸的主要过程，即使在零温度下的温度下增加，因此在非生长季节（NGS；秋季，冬季，春季）的二氧化碳排放量也随着气候的温暖而增加。除了微生物代谢活性的温度依赖性外，还可以通过土壤冷冻抑制NGS期间的土壤有机物分解，这限制了分子氧（O2）的供应（O2）和液态水的可用性。因此，对温度响应与拆分水的供应对低温下土壤二氧化碳生产的影响之间的分配的全面了解不仅对于预测北部陆地生态系统中易受伤害的碳库存的命运至关重要，而且对于准确的碳余额预测以及创造气候适应和缓解策略而言。拟议的发现赠款计划旨在填补我们对冷冻土壤中二氧化碳产量的温度依赖性以及土壤生物地球化学对冬季气候变暖的短暂反应的基本差距。所提出的方法结合了气相和水相化学的详细测量，以量化冻融周期中土壤微生物呼吸的速率，以及微生物群落结构的变化以及温度和未脱水的水含量对微生物介导的土壤CO2二氧化碳的交互作用。实验室实验旨在评估调节主要微生物代谢过程的土壤水物质参数以及生物地球化学速率和通量。实验结果将改善基于过程的基本理解，对冬季土壤生物地球化学过程，并将集成在反应性运输和生物能学建模中，以模拟在可变的冬季变暖场景下的碳和养分和微生物反应网络的生物地球化学转化。这将是我的发现赠款计划的长期目标迈出的重要一步，旨在通过确定在当前和未来气候变化的情况下，通过识别冬季土壤地质生物活动的主要生物地球化学驱动因素来预测地模拟寒冷地区地下环境中的反应动态基础。这项发现赠款研究的结果将是一种有价值的知识翻译工具，可促进北部生态系统中碳动态气候敏感性的科学数据和知识的渗透以及发展强大的气候变化适应策略。拟议的研究将为学生提供创新和增强的培训，以及在学术，政府或私营部门从事地球和环境科学的职业的竞争优势。