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

植物需要氮(N)来生存，但植物究竟在何时何地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。该项目研究了一个新的，更全面的角度对陆地氮循环，包括多个来源的氮从土壤。这项研究的重点是以前被忽视的矿物相关有机质（MAOM）作为植物氮供应的潜在主要驱动因素的作用。长期存在的理论认为MAOM在很大程度上是植物和微生物无法接近的，但新出现的证据强调了重新检查这种大规模分类的必要性。本研究考察了根系周围土壤MAOM的潜在供氮能力，这是一个关键的养分热点。最终，这些结果为MAOM作为生物可利用氮介质的作用提供了新的见解，这将挑战我们对陆地生态系统中调节土壤氮循环过程的基本认识。这项工作涉及参与俄克拉荷马州立大学的一个项目，该项目旨在提高代表性不足的人群对STEM学科的参与。该项目还支持与俄克拉何马州保护委员会合作，开发一个由学生主导的土壤生物地球化学研讨会和视频系列，具体涉及土壤有机质和MAOM管理。总体目标是量化和表征MAOM提供生物可利用氮的内在和植物介导的能力。指导假设强调MAOM-N供应依赖于MAOM的内在物理化学特性，MAOM相对于其他形式的土壤有机质的生物可利用性，以及植物-微生物机制，可以促进从MAOM中调动N。本项目的目标是：1)研究调节植物和微生物对MAOM-N获取的土壤因子；2)确定MAOM-N动员的机制；3)评估植物地下碳投资与MAOM-N动员之间的反馈关系。该研究利用实验室和温室试验评估了土壤地球化学性质的变化。实验操作与稳定同位素示踪相结合，可以追踪maom衍生的N进入生物可利用池，以及微生物和植物的吸收。该奖项反映了美国国家科学基金会的法定使命，并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，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.