Results/Conclusions Our model captures many essential characteristics of carbon-nitrogen interactions, and is capable of broadly recreating spatial and temporal variations in global nitrogen and carbon dynamics. The introduced nitrogen dynamics allows us to capture empirically observed responses in net primary production to step changes in carbon dioxide, while a carbon-only model fails to do this. Consistent with theories of successional dynamics, we find that physical disturbance induces strong carbon-nitrogen feedbacks, caused by intermittent nitrogen loss and subsequent nitrogen limitation. In contrast, carbon-nitrogen interactions are weak when the coupled model system approaches equilibrium. Thus, at steady-state many simulated features of the global carbon cycle, such as primary productivity, carbon inventories, and biogeography are similar to simulations that do not include nitrogen feedbacks. A surprising and potentially important finding is the possibility of a change in the terrestrial carbon cycle over the last twenty years. We discuss the evidence and implications of such a change.