Dissertation Research: Linking shifts in microbial community composition and N cycling to multiple global change factors in a California grassland

人类引起的环境变化有能力改变土壤养分循环，从而影响人类所依赖的许多生态系统服务。然而，尽管这些变化往往是同时发生的，但很少有研究调查它们对生态系统重要的地下组成部分的相互影响。由于氮（N）是大多数陆地系统中植物生长的限制性营养元素，因此了解氮循环如何响应生物和非生物变化至关重要。该项目将通过评估土壤微生物如何介导氮循环对环境中三个主要变化的相互作用做出贡献：氮沉积升高，放牧和入侵植物。土壤已被采样从下面的植物群落进行模拟氮沉降，牛放牧，并经历了外来植物物种的入侵。将从土壤中提取微生物DNA，以了解氮循环微生物对处理的反应。微生物群落的变化将与氮循环过程的变化相关。该项目的结果将有助于对负责氮循环关键步骤的微生物群落水平变化的新见解，最终有助于推进陆地生态系统营养动态的现有知识。项目成果将在国家和国际会议上介绍，如国际微生物生态学会，以确保在科学界广泛传播。将通过培训两名本科生全面参与研究项目来发展劳动力。此外，研究结果将发表在同行评审的期刊上，研究结果将通过研讨会向当地社区介绍。由于加州大学默塞德位于中央谷，接受外展的学生中很大一部分将来自代表性不足的群体。

Human-induced changes in the environment have the ability to alter soil nutrient cycles, thereby affecting the many ecosystem services on which humans rely. However, despite the fact that these changes often occur simultaneously, few studies have investigated their interactive effects on the important belowground components of an ecosystem. Because nitrogen (N) is the limiting nutrient for plant growth in most terrestrial systems, it is essential to understand how N cycling responds to both biotic and abiotic changes. This project will contribute to global change ecology by assessing how soil microorganisms that mediate N cycling respond to the interaction of three primary changes in the environment: elevated N deposition, cattle grazing, and invasive plants. Soil has been sampled from beneath plant communities that were subjected to simulated N deposition, cattle grazing and experienced the invasion of an exotic plant species. Microbial DNA will be extracted from the soil to understand how N-cycling microorganisms respond to the treatments. Changes in the microbial community will then be related to changes in N cycling processes. Results from this project will contribute new insight into community level changes in microorganisms that are responsible for key steps in the N cycle, ultimately helping to advance current knowledge of nutrient dynamics in terrestrial ecosystems. Project results will be presented at national and international conferences, such as the International Society of Microbial Ecology, in order to ensure widespread dissemination across the scientific community. Workforce development will occur through the training of two undergraduates by their full participation in the research project. Additionally, the results will be published in peer-reviewed journals and findings will be presented to the local community via seminars. Because the University of California, Merced, is located in the Central Valley, a large proportion of the students who receive outreach will be from underrepresented groups.