CAREER: Manganese biogeochemistry and impacts on carbon storage in plant-soil systems

土壤含有大量的有机物，它们既能改善土壤健康，又能通过储存碳(C)来调节大气中的二氧化碳水平。锰（Mn）等金属可以通过影响植物生长和帮助稳定或降解土壤中的有机化合物来影响土壤中有机C的储存量。本研究将探讨土壤和植物之间的锰循环如何影响陆地生态系统中有机碳的储存。该项目还将为研究生和本科生以及K-12教育工作者和学生创造一个教育机会网络。教育目标是通过克利夫兰自然历史博物馆（CMNH）向地区K-12教育工作者分发地球科学活动，提高科学素养，将研究与教育结合起来，扩大对地球科学的参与。该项目还将为多个研究生和本科生提供培训，他们将成为项目研究和教育部分不可或缺的参与者。锰是一种具有重要生物学意义和氧化还原活性的微量金属，可能对陆地生态系统的碳循环起着鲜为人知的控制作用；然而，锰增加或减少长期碳储存的机制仍不清楚。尽管大量的研究致力于了解铁和铝氧化物如何稳定有机碳，但关于锰氧化物的类似信息却很缺乏。此外，土壤地球化学如何调节植物对Mn的吸收，以及叶片Mn升高如何影响凋落物分解过程中碳的损失和转化也存在不确定性。本研究的总体假设是植被调节了陆地系统中锰的地球化学特征，并对土壤中的有机碳储量产生了次要影响。这一假设的含义是，锰是全球碳循环的一个未被认识但重要的调节剂。本研究将整合多个尺度的研究，探索锰生物地球化学的三个主要组成部分及其对关键带碳循环的影响：(1)地球化学对森林植被锰循环速率的控制；(2)叶片Mn升高对凋落物分解过程中有机碳释放量和化学成分的影响；(3)锰氧化物对有机物储存或转化的影响。研究结果将整合到描述植物-土壤系统中锰-碳相互作用的定量框架中，并为未来锰生物地球化学和耦合金属-有机相互作用的探索奠定基础。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。

Soils contain large quantities of organic matter that both improve soil health and regulate atmospheric carbon dioxide levels by storing carbon (C). Metals such as manganese (Mn) can influence how much organic C is stored in soils by impacting plant growth and by helping to either stabilize or degrade organic compounds in the soil. This research will explore how Mn cycling between soils and plants influences storage of organic C in terrestrial ecosystems. This project will also create a network of educational opportunities for graduate and undergraduate students as well as K-12 educators and students. The educational objectives are to improve science literacy, integrate research with education, and broaden participation in geosciences by distributing earth science activities to regional K-12 educators through the Cleveland Museum of Natural History (CMNH). This project will also provide training for multiple graduate and undergraduate students who will be integral participants in both the research and educational components of the project.Manganese is a biologically important and redox-active trace metal that may exert a poorly recognized control on carbon cycling in terrestrial ecosystems; however, the mechanisms by which Mn increases or decreases long-term carbon storage remains unclear. Although substantial research has been devoted to understanding how iron and aluminum oxides stabilize organic carbon, there is a scarcity of similar information regarding Mn oxides. Added to this knowledge gap are uncertainties related to how soil geochemistry regulates plant uptake of Mn, and how elevated foliar Mn impacts carbon loss and transformation during litter decomposition. The overarching hypothesis of this research is that vegetation regulates the geochemistry of manganese in terrestrial systems with secondary effects on organic carbon storage in soils. The implication of this hypothesis is that Mn is an unrecognized but significant regulator of the global C cycle. This research will integrate studies across multiple scales to explore three major components of manganese biogeochemistry and associated impacts on carbon cycling in the critical zone: (1) geochemical controls on rates of Mn cycling by forest vegetation; (2) influence of elevated foliar Mn on the quantity and chemical composition of organic C released during litter decomposition; (3) influence of Mn oxides on the storage or transformation of organic matter. Results will be integrated into a quantitative framework describing Mn-C interactions in plant-soil systems and lay the groundwork for future exploration of manganese biogeochemistry and coupled metal-organic interactions.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.