Fig. 2

Estimates of soil microbial NUE by the ¹⁸O-based method for N addition treatments. CK, control (0 kg N ha⁻¹ year⁻¹); LN low N addition (25 kg N ha⁻¹ year⁻¹), MN medium N addition (50 kg N ha⁻¹ year⁻¹), HN high N addition (75 kg N ha⁻¹ year⁻¹). Different letters indicate a significant difference among N addition treatments in a specific month. Data presented are mean and standard error (n = 3)