Hypothesis
Intercropping trees with a crop would raise soil microbial diversity along with soil fertility, relative to poplar monoculture.
What failed
High-throughput sequencing showed no significant effect of intercropping on bacterial or fungal alpha diversity, even though total phosphorus rose, the carbon-to-nitrogen ratio fell and community composition shifted, with fungal composition up and bacterial composition down.
Broken assumption
Mixing plant species above ground raises microbial diversity in the soil below.
Why
The abstract gives no explanation for the diversity null; the authors report that phosphorus correlated most strongly with bacterial diversity and pH with fungal diversity.
From the published paper: Liu et al. Frontiers in Microbiology, 2024. ↗CC BY