Johnson and her students study interactions among communities of plants and soil organisms in natural and human managed ecosystems throughout the world. They have discovered that mycorrhizae are sensitive to global change factors and are seeking first principles to understand these responses. Mycorrhizal changes may be a symptom or a driver of plant community shifts that occur when ecosystems experience changes in climate or resource availability. These studies are important because mycorrhizae influence plant community composition and soil erosion potential. Organic farmers and natural area managers will benefit from utilizing mycorrhizae as natural fertilizers but this goal is unachievable without a better understanding of the factors controlling mycorrhizal function.