Figure 4. Chao 1 index of soil microbial diversity under conventional management (CM) or intensive management (IM) and three N addition treatments.

N30: 30 kg N∙ha⁻¹∙yr⁻¹; N60: 60 kg N∙ha⁻¹∙yr⁻¹; N90: 90 kg N∙ha⁻¹∙yr⁻¹. Lowercase letters indicate significant differences between N addition treatments under IM(P < 0.05). Capital letters indicate significant differences between N addition treatments under CM(P < 0.05).Asterisks indicate significant differences between CM and IM at the same N addition rate (*P < 0.05, **P < 0.01). Values represent means of three replicates, and error bars indicate standard errors.