Collaborative Research: Mineral-associated organic matter: an overlooked source and mediator of bioavailable nitrogen

植物需要氮(N)才能生存，但植物在哪里、何时以及如何从土壤中获得足够的氮仍然是一个谜。这种N困境限制了生产力，并导致在自然和管理系统中预测和管理N循环的挑战。该项目研究了一种新的、更全面的关于陆地氮循环的观点，包括土壤中氮素的多个来源。这项研究的重点是之前被忽视的矿物相关有机质(MAOM)作为植物氮素供应的潜在主要驱动因素的作用。长期以来的理论认为，毛霉在很大程度上是植物和微生物无法接触到的，但新的证据突显了重新审视这种大规模分类的必要性。这项工作考察了毛姆在根围土壤区域的潜在供氮能力，这是一个关键的营养热点。最终，这些结果为MAOM作为生物有效氮的中介体的作用提供了新的见解，这将挑战我们对陆地生态系统中土壤N循环调节过程的基本理解。这项工作涉及参与俄克拉荷马州立大学的一个项目，该项目旨在增加代表不足的人群在STEM学科中的参与度。该项目还支持与俄克拉荷马州自然保护委员会合作，开发一个学生主导的关于土壤生物地球化学的讲习班和视频系列，与土壤有机质和土壤有机碳管理特别相关。总体目标是量化和表征MAOM提供生物有效氮的内在和植物介导的能力。指导性假说强调MAOM-N的供应依赖于MAOM的内在物理化学性质、MAOM相对于其他形式土壤有机质的生物有效性以及有助于从MAOM中动员N的植物-微生物机制。该项目追求以下目标：1)研究调节植物和微生物获得MAOM-N的土壤因素；2)确定驱动MAOM-N动员的机制；3)评估植物对地下碳的投资和MAOM-N动员之间的反馈。这项研究通过实验室和温室实验评估了土壤的不同地球化学性质。实验操作与稳定同位素示踪相结合，允许将MAOM衍生的N追踪到生物可用池中，以及被微生物和植物吸收。该奖项反映了NSF的法定使命，并通过使用基金会的智力优势和更广泛的影响审查标准进行评估，被认为值得支持。

Plants need nitrogen (N) to survive, but it remains a mystery exactly where, when, and how plants acquire enough N from the soil. This N dilemma limits productivity and leads to challenges in predicting and managing N cycling in natural and managed systems. This project examines a new, more holistic perspective on the terrestrial N cycle that encompasses multiple sources of N from the soil. The research focuses on the previously overlooked role of mineral-associated organic matter (MAOM) as a potential major driver of N supply to plants. Long-standing theories consider MAOM to be largely inaccessible to plants and microbes, but emerging evidence highlights the need to re-examine this wholesale classification. This work examines the potential N-supplying capacity of MAOM in the zone of soil surrounding roots, a critical nutrient hotspot. Ultimately, the results provide new insights into the role of MAOM as a mediator of bioavailable N, which will challenge our fundamental understanding of the processes that regulate soil N cycling in terrestrial ecosystems. The work involves participation in a program at Oklahoma State University, which aims to increase the participation of under-represented populations in STEM disciplines. The project also supports a collaboration with the Oklahoma Conservation Commission to develop a student-led workshop and video series on soil biogeochemistry with specific relevance to soil organic matter and MAOM management. The overarching objective is to quantify and characterize the intrinsic and plant-mediated capacity of MAOM to supply bioavailable N. The guiding hypothesis emphasizes the dependence of MAOM-N supply on the intrinsic physical-chemical properties of MAOM, the bioavailability of MAOM relative to other forms of soil organic matter, and plant-microbial mechanisms that can facilitate the mobilization of N from MAOM. The project pursues the following objectives: 1) Examine edaphic factors regulating plant and microbial access to MAOM-N; 2) Identify mechanisms driving MAOM-N mobilization; 3) Assess feedbacks between plant investment in belowground carbon and MAOM-N mobilization. The study assesses soils varying in geochemical properties using laboratory and greenhouse experiments. Experimental manipulations combined with stable isotope tracing allow for the tracing of MAOM-derived N into bioavailable pools, as well as uptake by microbes and plants.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.