| Summary: | Strong scientific evidence supports that anthropogenic activities since industrialization have caused instability in earth’s climate, featured by increasing global surface temperature, increasing greenhouse gas concentration in the atmosphere. Climate change has then caused a series of changes in the earth’s ecosystems, which can have significant impacts on the biosphere and our human being. Although huge efforts have been put into the research in climate science since the past century, due to the complexity of the climate system and its broad and long-lasting influence, there are still countless question marks and uncertainties in our understanding of climate change and its influence on earth and human society. Microorganisms are among the tiniest groups of life, but play important roles in the cycling of carbon and other nutrient elements in the biosphere. However, their response and feedback to climate warming in different ecosystems is still difficult to predict, limited by the lack of mechanistic understanding of the complex microbial community, their functions, their interactions among themselves and under warming perturbation. With the fast advance of high-throughput metagenomic technologies and the development of environmental microbiology, deep and detailed characterization of microbial diversity and functions became available, which provided great chances in promoting our insights into the mechanisms by which microbial communities mediate the carbon balance in a warmer world. This dissertation applied several metagenomic technologies to probe the soil microbial community responses to warming and permafrost thaw based on field observations and experiments in two ecosystems, a permafrost underlain Alaska tundra, and a temperate tall grass prairie in Oklahoma. Microbial decomposition of soil carbon in high latitude tundra underlain with permafrost is one of the most important, but poorly understood, potential positive feedbacks of greenhouse gas emissions from terrestrial ecosystems into the atmosphere in ...
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