Collaborative Research: Elucidating unifying principles of soil carbon-nitrogen coupling using a continental-scale grassland experimental network

人类活动，如作物上的肥料使用，大豆作物的种植和化石燃料燃烧，正在增加大气中循环的氮气量，并在雨雪中下降，称为氮沉积。大量氮沉降对世界各地生态系统的全面影响尚不清楚。特别是，氮沉降如何改变土壤中碳的数量和形式，人们知之甚少。然而，更好地理解氮和碳循环之间的所谓耦合对地球上的生命很重要。植物和土壤每年与大气交换大量的二氧化碳，因此交换速率的微小变化可能会影响空气中二氧化碳上升的速度。该项目将整合广泛的跨站点，协调的实地实验与建模的结果，以提高我们的地下碳和氮在草地生态系统中的耦合机制的理解。这是用于预测人类引起的全球环境变化的地球化学后果和改进碳循环对气候变化反馈的预测的地球系统模型的一个关键知识差距。 该项目还将使研究人员与锡达溪长期生态研究项目的教育和外展计划建立联系。这些计划旨在培训K-12学生和教师，增加妇女和其他代表性不足的群体成员在科学领域的参与和保留，特别注重指导本科生美洲原住民的研究。项目调查人员还将指导研究生和博士后学者。这项研究将使用北美草原长达十年的营养素添加实验网络，营养素网络，研究增强的氮输入如何影响土壤微生物动力学，土壤碳循环和二氧化碳释放到大气中。研究结果将用于增强微生物酶分解（MEND）模型，以确定氮素输入如何影响：（1）通过改变植物输入土壤的数量和质量，以及土壤微生物群落结构，化学计量和功能潜力，土壤有机质（SOM）的生物化学稳定性;（2）通过改变土壤团聚体形成和SOM-矿物相互作用，土壤有机质的物理化学稳定性。 生态系统碳和氮循环的计算机模拟模型的结果将通过能源部的能源加速气候模型方案提供给广大科学界。拟议工作产生的所有数据也将通过营养网络研究项目和长期生态研究网络提供。

Human activities such as fertilizer use on crops, cultivation of soybean crops, and fossil fuel burning are increasing the amount of nitrogen gas that is circulating in the atmosphere and coming down in rain and snow in what is known as nitrogen deposition. The full impacts of high amounts of nitrogen deposition on ecosystems around the world are not well known. In particular, how nitrogen deposition alters the amounts and forms of carbon in soils is very poorly understood. Yet, achieving better understanding of this so-called coupling between the nitrogen and carbon cycles is important for life on earth. Plants and soils exchange large amounts of carbon dioxide with the atmosphere each year and so small changes in the rate of that exchange could affect how fast carbon dioxide in the air is rising. This project will integrate results from extensive cross-site, coordinated field experiments with modeling to improve our mechanistic understanding of the coupling of belowground carbon and nitrogen in grassland ecosystems. This is a key knowledge gap for Earth system models used to predict the biogeochemical consequences of human-caused global environmental changes and to refine predictions of carbon cycle feedbacks to climate change. This project will also connect researchers with education and outreach programs of the Cedar Creek Long-Term Ecological Research project. These programs are aimed at training K-12 students and teachers and increasing participation and retention of women and members of other underrepresented groups in science, with a special focus on mentoring undergraduate Native Americans in research. Project investigators will also mentor graduate students and post-doctoral scholars. This research will use a network of decade-long nutrient addition experiments in North American grasslands, the Nutrient Network, to study how enhanced nitrogen inputs influence soil microbial dynamics, soil carbon cycling, and the release of carbon dioxide to the atmosphere. Results will be used to enhance the Microbial ENzyme Decomposition (MEND) model towards determining how nitrogen inputs affect: (1) biochemical stabilization of soil organic matter (SOM) by altering the quantity and quality of plant inputs to soils, and soil microbial community structure, stoichiometry, and functional potential; and (2) physicochemical stabilization of SOM by altering soil aggregate formation and SOM-mineral interactions. Results of computer simulation models of ecosystem carbon and nitrogen cycling will be made available to the scientific community at large through the Accelerated Climate Model for Energy program at the Department of Energy. All data generated from the proposed work will also be made publically available through the Nutrient Network research project and the Long-Term Ecological Research network.