Collaborative Research: MRA: A functional model of soil organic matter composition at continental scale

有机质是大多数土壤的组成部分，为社会提供了不成比例的关键服务。土壤有机质由于其储存碳和养分并在分解过程中释放它们的作用，影响肥力和植物生长、水质和水量，以及全球气候。尽管对土壤有机质的研究已有一个多世纪，但预测土壤有机质的分布和功能仍然具有挑战性。影响土壤有机质的生态系统性质在小尺度和大尺度上差异很大，以往的许多研究都集中在单一的土壤类型或地理区域。鉴于微生物不可避免地会在几天到几千年的时间尺度上分解土壤有机质，科学家们继续就土壤有机质的性质以及为什么它会持续存在进行辩论。该项目旨在调和之前关于土壤有机质的组成以及控制其分解和向植物供应氮素能力的物理、化学和生物因素的争论。这项研究将把丰富的现有数据与国家生态观测网络(NEON)的新样本和测量结果结合起来。NEON是一个包括美国各地不同地点的监测网络。研究人员将测试一个新的量化框架，通过在地方到大陆尺度上对环境特征进行多种权衡，来预测土壤碳和氮的循环。该项目将培训研究生和本科生，包括那些在科学领域代表性不足的学生，并将为普通教育受众开发与土壤有关的课程。在单一的生态系统类型中形成了许多与土壤有机质相关的有影响力的科学概念，并努力预测其在大陆尺度上的分布和动态。叶片经济学图谱表明，植物多样性的许多方面沿着与快速投资回报和缓慢投资回报相对应的基本性状变异轴崩溃。然而，土壤的巨大异质性以及缺乏全面和标准化的数据阻碍了开发类似简单的框架来预测土壤生物地球化学过程的努力。该项目将测试土壤有机质性质和循环的变化是否可以用三个生态系统变化的基本轴来解释，这三个轴对应于快和慢的生物地球化学速率，每个轴都与气候、矿物、植物、微生物和有机分子之间的相互作用有关，并得到了理论和初步数据的支持。考虑每个轴上土壤样品的组成及其对过程速率的共同影响，可能有助于调和先前工作中展示的不同有机质持久性机制的重要性，从而改进对土壤有机质提供的关键生态系统功能的预测。为了测试这一模型，研究人员将收集有机质分子组成、地球化学和矿物学、短期和长期生物地球化学过程速率以及微生物功能基因的新测量结果，这些测量利用了现有和正在进行的数据以及从霓虹灯站点收集的样本。该项目将包括招募、教育和培训未来的科学、工程、技术和政策劳动力和领导力，以及从事区域到大陆尺度生物学基础研究所需的领导力，以及让不同的学习者和教育工作者参与区域到大陆尺度的研究和使用NEON的机会。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。

Organic matter is a component of most soil that provides disproportionate and critical services to society. Soil organic matter influences fertility and plant growth, water quality and quantity, and global climate, due to its roles in storing carbon and nutrients and releasing them during decomposition. Predicting the distribution and functions of soil organic matter remains challenging despite more than a century of research on this topic. The ecosystem properties that influence soil organic matter vary tremendously over small and large spatial scales, and many previous studies have focused on a single soil type or geographic region. Scientists continue to debate the nature of soil organic matter and why it persists, given that microorganisms can inevitably decompose it over timescales of days to millennia. This project aims to reconcile previous debates regarding what soil organic matter consists of, and the physical, chemical, and biological factors that control its decomposition and capacity to supply nitrogen to plants. The study will combine a wealth of existing data with new samples and measurements from the National Ecological Observatory Network (NEON), a monitoring network including diverse sites across the U.S. Researchers will test a new quantitative framework to predict soil carbon and nitrogen cycling by incorporating multiple trade-offs in environmental characteristics at local to continental scales. The project will train graduate and undergraduate students, including those from underrepresented groups in science, and will develop soil-related curricula for a general educational audience. Many influential scientific concepts related to soil organic matter were developed within single ecosystem types and struggle to predict its distribution and dynamics at continental scale. The leaf economics spectrum showed that numerous aspects of plant diversity collapse along a fundamental axis of trait variation corresponding to fast vs. slow return on investment. However, the tremendous heterogeneity of soil and the lack of comprehensive and standardized data has stymied efforts to develop a similarly simple framework for predicting soil biogeochemical processes. This project will test whether variation in soil organic matter properties and cycling can be explained by three fundamental axes of ecosystem variation corresponding to fast and slow biogeochemical rates, each linked to interactions among climate, minerals, plants, microbes, and organic molecules, as supported by theory and preliminary data. Consideration of the composition of individual soil samples along each axis, and their joint influence on process rates, may help reconcile the importance of distinct mechanisms of organic matter persistence demonstrated in previous work, and thereby improve prediction of critical ecosystem functions that soil organic matter provides. To test this model, the researchers will collect new measurements of organic matter molecular composition, geochemistry and mineralogy, short- and long-term biogeochemical process rates, and microbial functional genes that leverage existing and ongoing data and sample collection from NEON sites. The project will include recruitment, education, and training of the future scientific, engineering, technical, and policy workforce and leadership needed to pursue basic research on regional to continental scale biology, as well as opportunities to engage a diverse community of learners and educators in regional to continental scale research and the use of NEON.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.