Marked dominance of Actinomycetota and compositional shifts in bacterial communities in Brazilian dryland soils under land-use change.

Tropical dry forests are among the most threatened and least studied tropical forest ecosystems worldwide. The Caatinga, the largest tropical dry forest in South America, comprises preserved and agriculturally impacted areas, providing a valuable model system to investigate how semiarid soil bacterial communities respond to natural seasonality and land-use change. Here, we evaluated how land-use and seasonality shape microbial community structure and ecological strategies in soils from conserved forest (CEF) and agriculture-influenced areas (BEF) across rainy and dry seasons using a contig-based taxonomy approach combined with ANCOM-BC2 differential abundance analysis and co-occurrence networks inference. A total of 74 phyla and 1015 genera were identified, with marked predominance of Actinomycetota (61.4%). Seasonal responses were mainly detected in BEF, where Trebonia and Mycobacterium were enriched during the dry season, while Solirubrobacter was more abundant in the rainy season. Taxa putatively associated with plant growth promotion and biological soil crust formation were consistently detected in both areas, whereas oligotrophic and methanotrophic groups were more enriched in CEF and taxa related to biocontrol potential were more represented in BEF. The proportion of seasonal generalists was higher in CEF than in BEF, representing 86.0% and 46.6% of the detected taxa, respectively, suggesting greater temporal stability in conserved soils. Co-occurrence networks revealed that CEF exhibited a sparser and more modular structure, whereas BEF displayed a highly interconnected network. Notably, all module hubs belonged to Actinomycetota. Together, these findings demonstrate that land-use intensification reshapes bacterial ecological strategies and network organization, reducing community heterogeneity under agricultural management.