My research interests focus on two general themes: 1) carbon and nitrogen cycling in streams, rivers and soils (especially in the context of land-water interactions), and 2) watershed-scale carbon cycling and climate change. I am interested in carbon and nitrogen cycling at a range of scales ranging from the molecular composition and microbial use of dissolved organic molecules, to the biogeochemical cycling in streams and soil, to larger scale fluxes from watersheds and trace gas emissions to the atmosphere. A central theme of my research is the role of hydrology, both surface and ground water, in linking ecosystems and governing biogeochemical transformations. A second theme involves the role of permafrost and permafrost thaw in controlling ecosystem structure in boreal forest and arctic ecosystems.