Fig. 4

Interactions of N addition (N), warming (W), increased precipitation (IP), and decreased precipitation (DP) on soil CO₂ emission (a), CH₄ uptake (b), and N₂O emission (c) (left), and corresponding frequency distribution of interaction types across individual pairwise observations (right). Solid circles indicate means with ± 95% confidence intervals (CI). The number of observations is shown along the right axis. Interactive effects were additive (gray, where 95% CIs overlap zero); otherwise, effects were synergistic (blue) or antagonistic (orange)