I am an ecosystem biogeochemist interested in the interactions among carbon, nitrogen, phosphorus, and water cycles in ecosystems and in how those interactions constrain ecosystem responses to disturbance and to changes in carbon dioxide and climate. My work centers around ecosystem simulation models based on the resource optimization paradigm, the cycling of nutrients between soils and vegetation, and the inputs and losses of nutrients and water. Much of my work has been centered around arctic ecosystems but also includes ecosystems ranging from prairies to forest, including tropical, temperate deciduous, temperate evergreen, and boreal forests.