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Nitrogen, microbes and the human predicament: The ecology and relevance of nitrogen recycling.

机译：氮，微生物和人类困境：氮循环的生态和意义。

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This dissertation, Nitrogen, Microbes, and the Human Predicament: The Ecology and Relevance of Nitrogen Recycling, explores nitrogen cycling at a variety of scales and in several different systems. The introduction broadly reviews the ecological consequences of nitrogen fertilizer use in agroecosystems and discusses the impacts of organic and integrated agricultural practices on environmentally damaging nitrogen losses. It concludes with a discussion of the research needed to mitigate agricultural nitrogen pollution and a summary of the research questions explored in this dissertation. Chapter one, "Soil Food Webs and the Principles of Organic Agriculture," is a comparative study of soil biology in organic, integrated and conventional orchard management systems. The research described in this chapter compares a suite of ecological processes and several trophic levels of associated organisms among organic, integrated and conventionally managed orchard soils in an effort to better understand the relationship between agricultural management and soil food web structure and function and the implications for enhancing soil fertility and agroecosystem resilience, and reducing nitrogen pollution, three of the tenets of organic agriculture. Chapter two is a study called " Reduced Nitrate Leaching and Enhanced Denitrifier Activity and Efficiency in Organically Fertilized Soils." This study compares gaseous and leaching nitrogen losses following fertilization in organic, integrated and conventional apple orchards to evaluate how fertilizer management and soil denitrifier communities interact to mediate agricultural nitrogen losses. Chapter three, "Fine Roots in an Old Growth Forest of the Pacific Northwest," looks at root phenology and turnover in relation to changing environmental factors in an old growth forest in Western Washington. Following the summary of research conclusions is a final chapter that attempts to integrate my scientific education with some of the wider knowledge and experience that I have been exposed to at Stanford and in Haiti. "Liberation Ecology, Nitrogen and Haiti: From Human Rights to Humus," explores some of connections between the themes discussed in the overview regarding the importance of doing relevant ecology, my education in nitrogen cycling, and the work I hope to do in the future.
机译：本论文《氮，微生物和人类困境：氮循环的生态学和相关性》探讨了各种规模和几个不同系统中的氮循环。导言广泛地回顾了农业生态系统中氮肥的生态后果，并讨论了有机和综合农业实践对破坏环境的氮素损失的影响。最后对减轻农业氮污染所需的研究进行了讨论，并对本文研究的问题进行了总结。第一章“土壤食物网和有机农业原理”是对有机，综合和常规果园管理系统中土壤生物学的比较研究。本章描述的研究比较了有机，整合和常规管理的果园土壤中的一系列生态过程和几种营养水平，以更好地了解农业管理与土壤食物网结构和功能之间的关系以及对农业的影响。增强土壤肥力和农业生态系统的适应力，减少氮污染是有机农业的三大宗旨。第二章是一项名为“减少有机肥土壤中硝态氮淋失，提高反硝化活性和效率的研究”。这项研究比较了有机，综合和常规苹果园施肥后的气态氮和浸出氮损失，以评估肥料管理和土壤反硝化菌群落之间如何相互作用来调节农业氮的损失。第三章，“西北太平洋老林中的细根”，探讨了华盛顿西部老林中与环境因素变化有关的根物候和周转。研究结论摘要之后的最后一章试图将我的科学教育与我在斯坦福大学和海地所接触到的更广泛的知识和经验相结合。 “解放生态，氮与海地：从人权到腐殖质”探讨了概述中讨论的主题之间的一些联系，这些主题涉及进行相关生态学的重要性，我对氮循环的教育以及我将来希望做的工作。

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