Understanding interactions between carbon (C) and nitrogen (N) cycling has been central to past progress and ongoing work in climate change research. Arvin Mosier has been a leader in investigating the coupled biogeochemical cycles of C and N in agroecosystems. His research and integrated approach have significantly increased our understanding of the responses of these systems to global change.

Rising atmospheric carbon dioxide (CO₂) levels can have direct effects on plant productivity and also important indirect effects on ecosystem biogeochemical cycles. An open-top chamber elevated atmospheric CO₂ study was initiated in 1997 in the shortgrass steppe of northeastern Colorado to examine the responses of ecosystem dynamics to elevated CO₂ and the potential impacts of elevated CO₂ on ecosystem sustainability. This large, collaborative effort focused on changes in ecosystem cycling of water, carbon, and nitrogen with exposure to elevated CO₂.

Elevated atmospheric CO₂ conditions resulted in significantly higher aboveground plant biomass production and significantly lower plant tissue nitrogen concentrations. The combination of these responses resulted in higher net removal of N from experimental plots treated with elevated CO₂. Such changes in N cycling are expected to limit the stimulation of ecosystem productivity under elevated CO₂ by slowing decomposition rates and by reducing soil N availability. However, no changes in decomposition rates of aboveground plant tissue or in trace gas fluxes in response to elevated CO₂ treatment were observed. Measurements of soil carbon cycling may help to elucidate changes in nitrogen cycling under elevated CO₂ conditions.