Impact of intensive agricultural management on soil biota in mountain ecosystems of the Brazilian Atlantic Forest

Mountain ecosystems in tropical regions are increasingly vulnerable to human activities, with changes in soil management significantly impacting the structure and activity of edaphic communities. This study adopts an integrative approach to assess soil quality by combining classical biological indicators with high-resolution molecular tools in areas under intensive agricultural management within a mountainous region of the Brazilian Atlantic Forest. Three sites were selected: two agricultural areas cultivated with tomato (Solanum lycopersicum L.) and maize (Zea mays L.), and a secondary forest with minimal anthropogenic disturbance. Soil macrofauna, the activity of β-glucosidase and arylsulfatase, and the abundance of arbuscular mycorrhizal fungi (AMF) were evaluated. Bacterial and fungal communities were characterized through high-throughput sequencing of the 16S rDNA and ITS regions. Macrofauna richness was highest in the forest and maize areas, while the tomato area exhibited the lowest species richness and density. Enzymatic activity varied across areas: β-glucosidase activity peaked in maize cultivation, while arylsulfatase proved to be a more sensitive indicator of soil degradation, decreasing with increased soil management intensity. Bacterial networks revealed more competitive interactions in cultivated areas, whereas cooperative associations dominated in the forest area. Fungal networks were more connected and structurally stable in the forest area, indicating higher ecological integrity. Overall, biological attributes effectively distinguished intensively managed agricultural soils from forest soils. The combined use of functional biological indicators and high-resolution molecular tools provides a sensitive, detailed assessment of soil biological responses to intensive agriculture in fragile mountain ecosystems, underscoring its detrimental effects on soil functional biodiversity.