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

人类活动，如在农作物上使用化肥、种植大豆作物和燃烧化石燃料，正在增加在大气中循环的氮气的数量，并在雨雪中落下，这就是所谓的氮沉积。大量氮沉积对世界各地生态系统的全面影响尚不为人所知。特别是，氮沉积如何改变土壤中碳的数量和形式还知之甚少。然而，更好地理解氮循环和碳循环之间的这种所谓的耦合对地球上的生命来说是重要的。植物和土壤每年都会与大气交换大量二氧化碳，因此这种交换速度的微小变化可能会影响空气中二氧化碳上升的速度。这个项目将把广泛的跨地点、协调的田间实验的结果与建模结合起来，以提高我们对草原生态系统地下碳和氮耦合的机制的理解。对于地球系统模型来说，这是一个关键的知识缺口，这些模型用于预测人类造成的全球环境变化的生物地球化学后果，并改进对气候变化的碳循环反馈的预测。该项目还将把研究人员与雪松溪长期生态研究项目的教育和推广项目联系起来。这些计划旨在培训K-12年级的学生和教师，增加妇女和其他代表不足的群体成员在科学领域的参与和留住，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养分添加实验网络-养分网络-来研究增加的氮素输入如何影响土壤微生物动态、土壤碳循环和向大气释放二氧化碳。结果将被用来加强微生物酶分解(MEND)模型，以确定氮输入如何影响：(1)通过改变植物输入到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来稳定土壤有机质(SOM)；以及(2)通过改变土壤团聚体形成和SOM-矿物相互作用来稳定土壤有机质。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加速能源气候模型计划向广大科学界提供。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向公众公布。

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.