Plants host diverse and dynamic microbial communities that play key roles in plant health and ecosystem function. As an inherently multidisciplinary field, plant microbiology has recently gained prominence in global change research. Understanding how microbial communities assemble locally and distribute across larger spatial scales is vital for predicting the impacts of global change on both microbes and plant health. My research explores the diversity and biogeographical patterns of plant-associated microbes, both above and belowground, to address fundamental questions in the macroecology of microes and offer insights into their responses to global change.