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.

高纬度寒冷地区的变暖速度是地球其他地区的两倍多，其中冬季变暖最为严重。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度以下的情况下也会随着变暖而增加，非生长季节（NGS；秋季、冬季、春季）的二氧化碳排放量预计将增加气候变暖。除了微生物代谢活动的温度依赖性外，NGS过程中土壤有机质的分解也会受到土壤冻结的抑制，这限制了分子氧（O2）的供应和未冻结液态水的可用性。因此，全面了解温度响应和未冻水可用性对低温下土壤二氧化碳产生的影响之间的分配不仅对于预测北部陆地生态系统脆弱碳储量的命运至关重要，而且对于准确预测碳平衡也至关重要制定气候适应和缓解战略。拟议的发现资助计划旨在填补我们对冻土中二氧化碳产生的温度依赖性以及土壤生物地球化学对冬季气候变暖的瞬态响应的理解的根本空白。该方法结合了气相和水相化学的详细测量，以量化冻融循环期间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冻水含量对土壤微生物呼吸的影响。微生物介导的土壤二氧化碳流出。实验室实验旨在评估土壤水物理参数以及调节主要微生物代谢过程的生物地球化学速率和通量。实验结果将提高对冬季土壤生物地球化学过程的基本过程的理解，并将整合到反应输运和生物能学模型中，以模拟不同冬季变暖情景下碳和养分以及微生物反应网络的生物地球化学转化。这将是我的发现资助计划的长期目标向前迈出的重要一步，即通过确定当前和未来气候变化下冬季土壤地球微生物活动的主要生物地球化学驱动因素，为预测模拟寒冷地区地下环境的反应动力学奠定基础。场景。这项发现补助金研究的成果将成为一个有价值的知识转化工具，有助于促进有关北方生态系统碳动态气候敏感性的科学数据和知识的渗透，并制定强有力的气候变化适应战略。拟议的研究将为学生提供创新和强化的培训以及在学术、政府或私营部门从事地球和环境科学职业的竞争优势。