I am intrigued by the causes of broad, general patterns in the biological diversity, structure and dynamics of ecosystems, in the benefits that society receives from natural and managed ecosystems, and in ways to assure environmental and social sustainability in the face of global increases in human consumption and population. I recently have focused on a related issue - the effects of biodiversity on the stability and functioning of ecosystems, which is scientifically intriguing and of great importance to society. Finally, I am interested in the impacts of human domination of global ecosystems, especially in the impacts of nitrogen deposition, habitat destruction/fragmentation, and invasive exotic species. I study mechanisms of resource competition among terrestrial plants, especially in the grasslands of Minnesota's Cedar Creek Ecosystem Science Reserve. This work has focused on causes of succession and controls of both diversity and species composition.