Soil bacterial richness, as measured by Shannon Diversity (<i>H’</i>) Index.

<p>The scores are displayed by grassland diversity levels: Monocultures or 1-way component (treatments 1–6), three 3-component polycultures (treatments 7–9), three 6-component polycultures (treatments 10–12), and a 12-component polyculture. Error bars represent ±1 SEM. Box plots with contrasting letters indicate significantly different means by Tukey’s HSD test.