ecological indices
N loading significantly decreased the values of MI25 (Fig. 3a), EI (Fig. 3c) and SI (Fig. 3d) while significantly increased the BI value (Fig. 3e) at 0-20 cm. MI25 (Fig. 3a) and SI (Fig. 3d) values significantly decreased with soil depth, and the CI value (Fig. 3f) significantly increased with soil depth. At 20-40 cm, the values of EI, SI, BI, and CI differed between N2 and N3.