Land use and bacterial community: taxonomic implications, metabolic potential and carbon dynamics in soil

The implications of the soil microbiome in carbon cycling is still poorly understood. We investigated the relationship between carbon dynamics and the structure of the bacterial community in different land uses. Soil samples were collected in integrated livestock-forest (ILF), crop-livestock (ICL), native forest (NF), and pasture (PP) systems. Five soil samples per area were collected down to 30 cm (0-5, 5-10, 10-20 and 20-30 cm) for soil organic matter fractionation (particulate - POM; mineral-associated - MAOM) and down to 10 cm for bacterial 16S rRNA gene (V3-V4) sequencing. Data were analyzed using ANOVA followed by Tukey’s or Kruskal-Wallis followed by Dunn’s (p < 0.05). Bacterial community composition was primarily shaped by land use. IPF was enriched in taxa associated with the formation of persistent carbon (e.g. Actinobacteriota), whereas NF was dominated by groups linked to high carbon turnover (e.g. Proteobacteria and Acidobacteriota), ILP and PP showed higher relative abundances of Firmicutes, indicative of rapid carbon cycling. Metabolic potential prediction based on 16S data revealed high functional redundancy among treatments, with the aminobenzoate degradation pathway being significantly higher in NF (0–5 cm), suggesting enhanced transformation of aromatic carbon. Finally, POM differed among treatments (0-5 cm), with higher values in NF, reflecting greater input and turnover of labile carbon. In contrast, MAOM was higher in IPF at 0-5 cm and 20-30 cm, indicating a greater potential for long-term carbon sequestration. These results highlight the relevance of the topic and demonstrate the ecological importance of land use and management for mitigating climate change.