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

我的研究计划的长期目标是了解在全球变化和土地利用管理下，土壤有机质(SOM)如何受到土壤微生物群落和植物相互作用的影响。SOM管理关键的生态系统服务，例如通过储存在SOM中的碳(C)来调节气候变化。维持和增加全球土壤有机质储量是一项全球优先事项，但也是一项持续的挑战，因为气候变化压力往往会加速土壤有机质的矿化。普遍的想法是，通过将有机质附着在土壤矿物质上的强烈化学作用，限制微生物的进入，从而保护土壤有机质不受微生物矿化的影响。因此，矿物伴生有机质库(MAOM)被认为是SOM中最相关的部分，可以用来理解SOM的长期保留和C封存。然而，这忽略了新出现的证据，即这个毛姆池很容易失去，很容易从矿物质中解离成溶解的有机物(DOM)，然后它可以被微生物淋滤或呼吸。这通常发生在洪水期间，当氧气耗尽时，MAOM从化学保护键释放到DOM中。在加拿大东部，随着气候变化，洪水强度和持续时间预计会增加，因此有必要更全面地了解洪水发生后SOM的脆弱性和滞留情况。为了理解控制土壤碳储存的机制，需要一个更准确的框架，考虑到洪水事件期间对MAOM和DOM之间交换的复杂生物物理控制。在接下来的五年里，我的目标是深入了解间歇淹水下生物物理控制如何影响MAOM和DOM之间的交换，并应用所获得的知识来更好地了解淹水对持久性SOM净平衡的影响。为了解决这一问题，我将综合三个短期目标的见解：1.确定土壤结构如何影响洪水期间土壤有机质的吸收和溶解，从而影响土壤有机质的净平衡。2.评价微生物对淹水的生长响应以及随后的结果对DOM-MAOM交换和C损失的影响。3.探索根际过程如何抵消或放大水淹对DOM-MAOM交换的影响。我的项目将产生急需的关于MAOM和DOM交换和SOM保留的基础知识，提供间歇性洪水和农业管理情景下SOM的更完整的图景，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毛姆对洪水的脆弱性。我的计划将培训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的专业知识，使他们成为土壤生物地球化学领域的领导者。

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.