Microbial diversity and abundance in different acidified soils from mature pomelo planting orchard

Summary Soil acidification poses significant threats to the ecological environment and agricultural productivity in southern China. However, the variations in soil microbial communities along the acidic gradient profile remain poorly understood. In this study, we investigated soil microorganisms across normal, acidic, and strongly acidic soil samples using high-throughput sequencing technology. We described their distribution characteristics under different acidification backgrounds and depicted their responses to ambient environment factors. Our findings indicated that the Actinobacteriota (41.84%), Proteobacteria (27.91%), Chlorofexi (13.86%), Ascomycota (75.69%) and Basidiomycota (19.00%) comprised the core microbial populations among the samples. Meanwhile, Xanthobacteraceae (3.13%), Acidothermus (2.16%), Sordariomycetes (10.05%) and Thysanophora (8.71%) were more abundant in acidified soils, suggesting a higher probability of soil-borne diseases. Furthermore, soil acidification exerted more negative effects on the bacterial community, as revealed by PICRUSt predictions showing significant decreases in the pathways of carbohydrate, lipid and protein metabolism. In contrast, the fungal community demonstrated relatively stronger resistance to acid stress, as evidenced by the increased abundance of pathways related to signal transition and cell proliferation. Overall, our study sheds light on the responses of soil microbial communities to acidification stress and underscores the differential impacts on bacterial and fungal populations.