Resource availability drives viral ecological strategies across soil depths

Soil viruses are critical modulators of microbial communities and biogeochemical cycles, yet how their ecological responses to environmental gradients like soil depth, carbon and nutrient availability remain poorly understood. We investigated soil viral communities in a long-term field experiment with distinct carbon and nutrient levels at two depths, 0-10 cm (top soil) and 10-20 cm (subsoil). In the subsoil, viral life strategies were related with prokaryotic growth rates, showing a positive correlation with the abundance of lysogenic viruses and a negative correlation with that of lytic viruses. This coupling was not observed in the topsoil. Viral species richness was higher in high-carbon soils than in low-carbon soils at both depths. The abundance of viral anti-CRISPR genes, which encode proteins that disable host defense systems, increased by 2- to 3-fold in soils with both high carbon and nutrient availability compared to soils with high nutrient but low carbon availability. Conversely, in high-carbon soils, the abundance of viral reverse transcriptase genes was reduced, suggesting a potential shift in viral diversification strategies in response to resource limitation. The function of viral auxiliary metabolic genes (AMGs) of carbohydrate-active enzymes (CAZymes) shifted from the degradation of recalcitrant cellulose in low-carbon soils to the breakdown of labile substrates in high-carbon environments. Collectively, our findings suggest that viral life strategies, anti-defense capabilities, and AMG functions are closely associated with both soil depth and resource availability, providing insights into understanding their context-dependent role in terrestrial ecosystems. • Viral ecological strategies in oxisols were investigated across different soil depths and resource availabilities. • Viral life strategies are tightly coupled with prokaryotic growth rates in resource-limited subsoils. • High resource availability promotes viral anti-defense mechanisms. • High carbon availability increases viral species richness. • Viral AMG functions shift from degrading recalcitrant cellulose to labile carbon with increased resource availability.