Growth Chamber mesocosm experiment to assess the effects of the OSS decoupled from the presence of G. senegalensis (PRJNA930014)

The Sahel region of West Africa is a vulnerable eco-region where a growing population and climate-change induced drought threaten food security. The subsistence farmers here grow pearl millet (Pennisetum glaucum) without fertilizers or irrigation. Local and biologically-based means of maintaining yields are needed, and an agroforestry system in Senegal - the Optimized Shrub-intercropping System (OSS) - provides a solution. In the OSS, the shrub Gueira senegalensis performs hydraulic lift, distributing deep subsurface water to neighboring millet plants. The shrub also supports a distinct microbial community and significantly improves carbon storage and nutrient dynamics. Here, we aimed to test whether shrub-impacted soils differed in microbiome and millet outcomes under simulated early-season drought in a growth chamber.  Shrub impact was separated into residual impacts on microbiome and soil, versus ongoing shrub-derived organic matter (OM) input. decoupled from the effects of the growing shrub. Methods: We characterized the microbiota through dry-down and rewetting periods, with particular attention to lineages with known plant growth promoting (PGP) properties, via  amplicon sequencing of the 16S rRNA gene V3-V4 region and the ITS2, . Results: Both bacterial and fungal communities were significantly altered by imposed drought, OM amendment, and original soil type (+/-OSS). The largest significant bacterial community impact under dry down occurred for +shrub/-OM treatments, and under rewetting for -OM treatment regardless of +/- OSS. Known bacterial PGP lineages were only enriched under drought in +OSS/-OM treatments. The fungal community behaved differently with a significant dry-down impact only in +OSS/+OM treatments, while rewetting  enriched for fungal pathogens but only in -OSS/+OM soils. Decoupled from ongoing shrub growth, both residual shrub impacts and shrub OM inputs altered microbiota and increased millet biomass under drought. These results are part of a growing body of work aimed at understanding microbiome roles in increasing ecological resilience and combating food insecurity. Metagenomic and amplicon sequencing data are publicly available via NCBI PRJNA930014. Here we present all associated soil chemical, enzyme, and plant physical and chemical data