Journal Article 2 Research Support, Non-U.S. Gov't 2 rising atmospheric CO2 142M471B3J 1 C4 grass 1 Carbon Dioxide 1 Food security 1 mehr ... N762921K75 1 Nitrogen 1 Research Support, U.S. Gov't, Non-P.H.S. 1 Soil 1 climate change 1 degradation 1 ecosystem services 1 grain yield 1 protein content 1 savanna 1 trends over time 1 wheat field trials 1 woody encroachment 1 weniger ...