Given the vast diversity of microorganisms and their relevance for environmental and human health, there remains a need to better understand the patterns and processes that fundamentally underlie the structure and function of microbial communities through space and time. In particular, soil bacterial communities are vital to ecosystems and agriculture as they largely control soil fertility, plant community dynamics, and global biogeochemical cycles. To this aim, my dissertation work builds understandings regarding the development of soil microbial communities and their function. First, I demonstrate the paramount role of nutrient limitation in controlling the assembly of autotrophic microbial communities through succession (Chapter 2), based on a nutrient manipulation experiment. This work shows that nitrogen (N) and phosphorous (P) fertilization act as a major control on microbial community succession. In Chapter 3, I examine the connections between environmental, community, and functional properties of microbes in post-fire successional soils. This work builds empirical evidence that relationships between resource environment and ecosystem function shift in relative strength across succession. This work also suggests the role of rRNA operon copy number as a trait that varies across succession and may serve future research in describing processes of microbial community assembly that connect environment, trait, and function. In Chapter 4, I continue to examine plant-microbe interactions, assessing how post-fire revegetation processes may drive post-fire secondary succession with implications for ecosystem function. This work also reveals that the abiotic context of the post-fire landscape may impact when and to what extent biotic factors, such as plant-microbe interactions, matter in structuring microbial communities and their function. The Appendix provides additional research that describes plant-microbe interactions in succession, assessing how the plant root environment may select for particular bacteria in early succession that range in generalist to specialist character. Overall, my work builds knowledge on the controls that may underlie changes in microbial community structure and function through succession, spanning a variety of scales including traits, communities, and ecosystem processes. My work advances our knowledge of how microbial communities assemble through succession and the resulting patterns in their composition and function, which can have immense implications for humans to ecosystems
