DISSERTATION RESEARCH: Connecting dryland soil trace gas emissions of NOx, N2O and CO2 to microbial community dynamics along a nitrogen deposition gradient

物种多样性和群落组成对生态系统过程的重要性已在植物和动物中得到证明，但对土壤微生物的研究较少。土壤微生物可能通过产生二氧化碳和氮氧化物等温室气体，在导致气候变化和空气污染的过程中发挥重要作用。科学家目前估计存在数百万到数十亿个微生物物种，但物种组成的变化如何与生态系统功能相关尚不清楚。这项研究将结合土壤产气量的测量和先进的DNA分析技术来研究土壤细菌和真菌的多样性，以解决以下问题：1)空气污染如何影响土壤微生物的物种组成，对生态系统过程有什么影响？2)微生物群落组成在多大程度上影响对气候变化和空气污染的反馈？这项研究将使用在南加州科罗拉多沙漠的实验操作来调查温度、土壤水分和养分有效性如何调节土壤微生物反馈。研究结果将增强对未来气候情景对生态系统过程影响的预测能力，并有助于加深对微生物生态学的理解。旱地占全球陆地面积的30%以上。旱地不断增加的人类活动加剧了空气污染，后果未知。了解微生物群落结构和土壤对全球变化驱动因素的反馈之间的关系可以为土地管理战略提供信息，并将其纳入农业实践，以减少污染和提高效率。此外，这项研究将告知监管机构，以便在制定排放标准时考虑土壤反馈。最后，该项目将为广大受众提供新的教育机会，包括来自当地学校的研究生、本科生和小学生。这些机会将以最近才出现的新环境基因技术为特色。从这项研究中获得的技能和知识将被纳入社区外联活动，旨在让当地小学和高中的孩子们对科学和大学机会感到兴奋。

The importance of species diversity and community composition for ecosystem processes has been shown in plants and animals, but fewer studies have focused on soil microorganisms. Soil microorganisms may play an important role in processes contributing to climate change and air pollution through production of greenhouse gases such as carbon dioxide and nitrogen oxides. Scientists currently estimate the existence of millions to billions of microbial species, but how changes in species composition relate to ecosystem function is not well understood. This study will combine measurements of soil gas production with advanced techniques for DNA analysis to examine diversity of soil bacteria and fungi to address the following questions: 1) How does air pollution affect species composition of soil microorganisms and what is the impact on ecosystem processes? 2) To what extent does microbial community composition influence feedbacks to climate change and air pollution? This study will use experimental manipulations in the Colorado Desert of southern California to investigate how temperature, soil moisture and nutrient availability regulate soil microbiological feedbacks. The results will increase predictive power for the impact of future climate scenarios on ecosystem processes, and contribute to a deeper understanding of microbial ecology. Drylands cover greater than 30% of the global land surface. Increasing human activity in drylands intensifies air pollution with unknown consequences. Knowledge of the relationships between microbial community structure and soil feedbacks to global change drivers can inform land management strategies and be incorporated into agricultural practices to reduce pollution and improve efficiency. Furthermore, this research will inform regulatory bodies so that soil feedbacks are considered when emission standards are set. Finally, the project will provide new educational opportunities to a wide audience, including graduate, undergraduate, and primary students from local schools. These opportunities will feature new environmental genetic techniques that have only recently become available. The skills and knowledge gained from the study will be incorporated into community outreach events that aim to excite children from local elementary and high schools about science and college opportunities.