Environmental drivers of soil virus diversity across UK habitats

Soil viruses are critical members of the soil microbiome, shaping terrestrial ecosystem processes and microbial dynamics. However, the environmental factors governing their landscape-scale biogeography remain poorly characterised. Here, we analysed bulk soil metagenomic data from the UKCEH Countryside Survey across broad habitat classes to identify the key drivers of viral diversity and community assembly in UK soils. We show that soil pH is the primary predictor of both viral species richness and overall community composition, alongside significant contributions from the co-related soil organic matter and broad habitat type. Viral species diversity exhibited a strongly non-linear relationship with pH, peaking in neutral to slightly acidic soils. Viral community dissimilarity strongly correlated with 16S rRNA bacterial community structure across all taxonomic ranks, with the strongest association at ASV-level resolution. Despite high spatial turnover among viral contigs, and significant habitat-specific enrichment of particular anti-phage defence systems, viral lifestyle proxies like integrase gene frequencies showed no habitat-specific variation. Together, our results demonstrate that UK soil viral communities are primarily structured by soil pH and habitat parameters and closely coupled to patterns of bacterial host distribution, providing a baseline for future investigations and monitoring of change.