Bill focuses on modeling terrestrial ecosystems and their interactions with climate and climate change. He has a varied educational background, including degrees in mechanical and aerospace engineering, physics, and civil and environmental engineering. His published work includes development, testing, and application of numerical models that represent soil microbial dynamics, effects of abiotic processes such as mineral surface interactions, nutrient competition between microbes and plants, watershed-scale hydrological and biogeochemical processes, and climate-scale carbon and nutrient cycle processes.