Nitrogen deposition in China has increased, affecting carbon dynamics in Chinese ecosystems. A meta-analysis of 88 studies found that adding nitrogen did not change soil carbon, but increased above-ground plant carbon while decreasing below-ground plant carbon. The impact of nitrogen on carbon dynamics varies by ecosystem type and nitrogen addition rate. The decrease in below-ground plant carbon may limit long-term soil carbon storage, suggesting that N-rich and N-limited ecosystems should be treated differently in modeling nitrogen effects on the carbon cycle.