Does nitrogen limit CO2 fertilization effects?

It is widely assumed in the literature that nitrogen (N) availability would limit stimulation of plant productivity under elevated CO₂. In general, elevated CO₂ enhances photosynthesis and stimulates plant growth and carbon input into terrestrial ecosystems. Increased carbon input generally requires more N under elevated than ambient CO₂ to support plant growth and, in turn, sequesters N into long-lived plant biomass. This N sequestration can decrease soil N availability for plant uptake and lead to N limitation on CO₂ fertilization effects. However, the N limitation may not occur if the terrestrial N cycle is not tightly closed.