Fig 6. Responses of net ecosystem CO₂ exchange (NEE, μmol m^-2 s^-1) to monthly precipitation regimes (A, frequency; B, amount; C, intensity; D, evenness) across the 3 years for both nitrogen fertilized (open circles, A: y = Exp(2.240 – 2.662x^-1); B: y = Exp(2.017 – 6.269x^-1); C: y = Exp(2.053 – 1.190x^-1); D: y = Exp(2.479 – 0.316x^-1)) and unfertilized plots (solid circles, A: y = Exp(1.905 – 3.610x^-1); B: y = Exp(1.613 – 9.101x^-1); C: y = Exp(1.700 – 1.983x^-1); D: y = Exp(2.141 – 0.381x^-1)).

Nitrogen fertilized plots include both N and WN plots, and unfertilized plots include both CK and W plots. Water addition was treated as a precipitation event and included in the calculation of monthly precipitation regimes. * and ** represent significant relationships at the P < 0.05 and P < 0.01 levels, respectively.