MCA: Characterizing Rhizosphere Decomposition with Novel Techniques in Contrasting Salt Marshes

盐沼为沿海社区提供了几种重要的生态系统服务。最有价值的服务之一是缓冲海岸，使其免受海平面上升和沿海风暴的破坏。沼泽地通过建造土壤和垂直生长提供这种服务。沼泽土壤主要由河流输送的矿物质和沼泽草的有机物组成。这些材料的运送可能受到人类活动的威胁。这使得有效掩埋和长期保存有机物以保持沼泽海拔变得更加重要。本研究探讨了控制土壤有机质保存的小尺度机制。实验室和现场实验正在测试三种保存机制如何在受控和自然条件下运作。研究结果有助于解释土壤碳储量的空间变异性，并可能为预测盐沼生存与海平面上升的模型提供信息。通过该项目获得的专业知识提供了职业发展和沿海碳科学的进步。高中生和本科生也通过格鲁吉亚的一个推广项目接触到这个科学项目。三种机制影响分解-氧的可用性，矿物质的保护，和根分泌物启动-正在研究使用新的地球化学和同位素示踪和成像技术。这些实验是基于两个长期生态研究地点--格鲁吉亚沿海生态系统和梅岛生态系统--它们具有相似的潮差、沼泽草和生产率，但碳储存率不同。在实验室中，矿物和有机根际土壤保持在好氧或缺氧条件下，以测试土壤碳是如何保存的。一个现场实验正在部署在这两个网站，以操纵潮汐驱动的氧化还原条件。这项研究增加了关于氧化还原条件如何影响碳转化的知识。根分泌物通过微生物结合或土壤颗粒稳定的命运有助于发现是什么使矿物和有机盐沼适应不断变化的海岸条件。该奖项反映了NSF的法定使命，并已被认为是值得通过使用基金会的知识价值和更广泛的影响审查标准进行评估的支持。

Salt marshes provide several important ecosystem services to coastal communities. One of the most valuable services is buffering coasts from damage due to rising sea levels and coastal storms. Marshes provide this service by building soils and growing vertically. Marsh soils are mostly made of minerals delivered by rivers and organic matter from marsh grasses. Delivery of these materials can be put at risk by human activities. This places additional importance on efficient burial and long-term preservation of organic matter in maintaining marsh elevation. This research examines the small-scale mechanisms controlling soil organic matter preservation. Laboratory and field experiments are testing how three preservation mechanisms operate under controlled and natural conditions. Results help explain spatial variability in soil carbon stocks and may inform models predicting salt marsh survival with sea-level rise. The expertise gained through this project provides both career development and advances in coastal carbon science. High school students and undergraduate students are also gaining exposure to this science project through an outreach program in Georgia. Three mechanisms affecting decomposition — oxygen availability, mineral protection, and root exudate priming — are being investigated using novel geochemical and isotope tracing and imaging techniques. The experiments are based at two Long-Term Ecological Research sites – Georgia Coastal Ecosystems and Plum Island Ecosystems – which have similar tidal ranges, marsh grasses, and production rates but different carbon storage rates. In the lab, mineral and organic rhizosphere soils are maintained under oxic or anoxic conditions to test how soil carbon is preserved. A field experiment is being deployed at both sites, to manipulate tidally-driven redox conditions. The research is adding knowledge about how redox conditions affect carbon transformations. The fate of root exudates through microbial incorporation or soil particle stabilization helps discover what makes both mineral and organic salt marshes resilient to changing coastal conditions.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.