Soil Nutrient Enrichment Induces Trade-Offs in Bacterial Life-History Strategies Promoting Plant Productivity

Despite the global prevalence of anthropogenic soil nutrient enrichment, its impacts on the trade-offs in microbial life-history strategies remain poorly understood, which is critical for agroecosystem productivity. Here, large-scale observational studies are integrated with controlled experiments to systematically evaluate how soil nutrient enrichment affects bacterial functional potential and growth-rate potential, ultimately determining microbial functions and plant productivity. These findings reveal stark contrasts between nutrient-poor open field (OF) and nutrient-rich greenhouse (GH) soils across multiple paired sites using 16S rRNA gene amplicon and metagenomic sequencing. OF microbial communities dominated by oligotrophs have higher taxonomic diversity, larger average genome sizes with abundant nutrient-cycling genes, but lower 16S ribosomal RNA gene operon copy numbers and predicted maximum growth rates. Conversely, GH communities dominated by copiotrophs have higher growth-rate potential, more plant-beneficial bacteria, and higher diversity of functional genes (e.g., biofilm formation, secondary metabolism, and bacterial chemotaxis), but lower bacterial functional potential. Controlled pot experiments demonstrate that GH-enriched microbial functions strongly promote plant growth, particularly under sufficient nutrients and abiotic stress. These findings reveal a nutrient-driven trade-off between bacterial functional potential and growth rate, with implications for optimizing nutrient management strategies in precision agriculture to enhance specific microbial functions and plant productivity.