Widespread anthropogenic changes to communities and ecosystems reinforce and reinvigorate our need to understand fundamental ecological questions. How do species interact? How do communities assemble? How do ecosystems function? Importantly, how do human impacts such as nutrient enrichment and land use change alter these processes? In this talk, I explore two main research areas that ask fundamental ecological questions in changing environments. First, I show that nutrient enrichment can dramatically alter relationships between grasses and arbuscular mycorrhizal fungi, but that different grass species respond differently to altered environmental conditions. This finding inspires one of my future research directions, which asks whether this mechanism influences community assembly in nutrient-enriched habitats. Second, I briefly explore causes of variation in beta diversity (spatial variation in species composition within a community) in post-agricultural habitats. This line of research motivates a second future research direction, which asks what effect these differences in beta diversity have on ecosystem function. Understanding these core ecological topics, species interactions and the causes of beta diversity, remain important goals for basic community ecologists. Today’s rapidly changing human-impacted ecosystems provide both inspiration and a testing ground for exploration of these core topics. My research program is rooted in the belief that knowledge of fundamental ecological processes and how they respond to altered environmental contexts is vital to our understanding of life around us.