Investigating interactions between mineral-associated and dissolved soil organic matter to improve understanding of soil carbon retention under intermittent flooding

研究矿物相关有机质和溶解土壤有机质之间的相互作用，以提高对间歇性洪水下土壤碳保留的了解

• 批准号: RGPIN-2021-03250
• 负责人: Kallenbach, Cynthia
• 金额: $ 2.55万
• 依托单位: McGill University
• 依托单位国家: 加拿大
• 项目类别: Discovery Grants Program - Individual
• 财政年份: 2021
• 资助国家: 加拿大
• 起止时间: 2021-01-01 至 2022-12-31
• 项目状态: 已结题
• 来源: https://www.nserc-crsng.gc.ca/ase-oro/Details-Detailles_eng.asp?id=742453
• 关键词: Investigating; interactions; between; mineral; associated

The long-term goal of my research program is to understand how soil organic matter (SOM) is impacted by the interactions of soil microbial communities and plants under global change and land-use management. SOM governs key ecosystem services such as regulating climate change through carbon (C) stored within SOM. Maintaining and increasing global SOM stocks is a global priority yet also a consistent challenge due to climate change stressors that often accelerate SOM mineralization. The prevailing thinking is that SOM is protected from microbial mineralization via strong chemical interactions that attached organic matter to soil minerals, limiting microbial access. Thus, the mineral-associated organic matter pool (MAOM) is considered the most relevant fraction of SOM for understanding long-term SOM retention and C sequestration. However, this overlooks emerging evidence that this MAOM pool is vulnerable to loss, easily disassociating from minerals into dissolved organic matter (DOM) where it can then be leached or respired by microbes. This often occurs during flood events when oxygen depletion releases MAOM from its chemical protective bonds into DOM. In Eastern Canada, increases in flood intensity and duration are expected with climate change, necessitating a more complete understanding of SOM vulnerability and retention following flood events. A more accurate framework that considers the complex biophysical controls on the exchanges between MAOM and DOM during flood events is needed to understand the mechanisms controlling soil C storage. Over the next five years my goal is to gain insights into how biophysical controls affect the exchanges between MAOM and DOM under intermittent flooding and to apply the knowledge gained to better understand flooding impacts on the net balance of persistent SOM. To address this, I will integrate insight from across three short-term objectives: 1. Determine how soil structure impacts sorption and solubilization of SOM during flood events and consequently the net balance of MAOM. 2. Evaluate the influence of microbial growth responses to flooding and the subsequent outcomes on DOM-MAOM exchanges and C loss. 3. Explore how rhizosphere processes counter-act or amplify flooding effects on DOM-MAOM exchange. My program will generate much needed fundamental knowledge of MAOM and DOM exchange and SOM retention, providing a more complete picture of SOM under intermittent flooding and agricultural management scenarios, priority goals for Canadian governments and land resource managers, including the agri-food sector. Novel outcomes from this program will explain how plant roots, soil microbial communities, and the soil physical environment impact MAOM vulnerability to flooding. My program will train 7 HQP who will gain expertise in molecular chemical and microbial techniques, isotope biogeochemistry, and designing and implementing experiments, positioning them to become leaders in the field of soil biogeochemistry.

我的研究项目的长期目标是了解全球变化和土地利用管理下土壤微生物群落和植物的相互作用如何影响土壤有机质（SOM）。 SOM 管理关键的生态系统服务，例如通过 SOM 中存储的碳 (C) 调节气候变化。维持和增加全球 SOM 储量是全球优先事项，但由于气候变化压力因素往往会加速 SOM 矿化，这也是一项持续的挑战。普遍的观点是，SOM 通过强烈的化学相互作用而免受微生物矿化，将有机物附着在土壤矿物质上，限制微生物的进入。因此，与矿物相关的有机质库 (MAOM) 被认为是了解长期 SOM 保留和碳封存最相关的 SOM 部分。然而，这忽视了新出现的证据，表明该 MAOM 池很容易损失，很容易与矿物质分离成溶解有机物 (DOM)，然后被微生物浸出或呼吸。这种情况通常发生在洪水事件期间，此时缺氧将 MAOM 从其化学保护键释放到 DOM 中。在加拿大东部，预计洪水强度和持续时间会随着气候变化而增加，因此需要更全面地了解洪水事件后 SOM 的脆弱性和保留情况。 需要一个更准确的框架来考虑洪水事件期间 MAOM 和 DOM 之间交换的复杂生物物理控制，以了解控制土壤碳储存的机制。在接下来的五年中，我的目标是深入了解生物物理控制如何影响间歇性洪水下 MAOM 和 DOM 之间的交换，并应用所获得的知识更好地了解洪水对持久性 SOM 净平衡的影响。 为了解决这个问题，我将整合来自三个短期目标的见解： 1. 确定土壤结构如何影响洪水事件期间 SOM 的吸附和溶解，从而影响 MAOM 的净平衡。 2. 评估微生物生长对洪水反应的影响以及随后对 DOM-MAOM 交换和 C 损失的结果。 3. 探索根际过程如何抵消或放大洪水对 DOM-MAOM 交换的影响。我的计划将产生急需的 MAOM 和 DOM 交换以及 SOM 保留方面的基础知识，提供间歇性洪水和农业管理情景下 SOM 的更完整概况，以及加拿大政府和土地资源管理者（包括农业食品部门）的优先目标。该项目的新成果将解释植物根系、土壤微生物群落和土壤物理环境如何影响 MAOM 对洪水的脆弱性。我的项目将培训 7 名 HQP，他们将获得分子化学和微生物技术、同位素生物地球化学以及设计和实施实验方面的专业知识，使他们成为土壤生物地球化学领域的领导者。