<b>Threshold Effect of SOM Molecular Diversity on the Relationship of Soil Health and Bacterial Community in Black Soil Ecosystems</b>

Sustaining black soil health is critical for ensuring crop productivity and supporting regional economies. Bacterial diversity is a well–established driver of soil health and crop yield. Despite the critical role of SOM molecular diversity in shaping bacterial communities, its influence on the bacterial diversity–soil health relationship remains unclear. To address this knowledge gap, 164 soil samples with a gradient of SOM molecular diversity were collected from the black soil region of Northeast China. The soil health index (SHI) was computed using the Cornell Soil Health Assessment framework, which integrates fourteen chemical, physical, and biological indicators.