Bacterial assemblies in acidic dryland vs. paddy soils across depth profiles in southern China's red soil region

Abstract

Red soils in China are essential for food security, ecological balance, and rural development. Red soil's varied microbial populations help maintain soil health, cycle nutrients, and sustain ecosystems. The variation in bacterial community assembly and distribution with soil depth in acidic dryland and paddy soils is unknown. We sampled dryland and paddy soil profiles from nearby farms in southern China's red soil region. Five soil layers (0–20 cm, 20–40 cm, 40–60 cm, 60–80 cm, 80–100 cm) were taken from a 1-meter soil profile at Yichun, Jiangxi, China. In paddy soils, ammonium nitrogen, available iron, and soil organic matter (SOM) were greater than in dryland soils. While both soil types showed considerable variation in diversity indices (Chao1, Sobs, PD) over the soil profile, paddy soils showed a more wave-like pattern in microbial diversity indicators. Dryland soils had higher relative abundances of Actinobacteriota (3.6–7.3 %) and GAL15 (1.3–8.6 %), while paddy soils had Bacteroidota (3.9–9.2 %), Desulfobacterota (4.2–7.7 %), and Nitrospirota (2.1–12.7 %). Acidobacteriota (29.5–59.1 %), Chloroflexi (6.3–30.9 %), and Proteobacteria (7.5–21.5 %) predominated at both soil types. Taxonomic alterations in Acidobacteriota, Chloroflexi, and Proteobacteria highlighted how microbial communities adapted to dryland vs paddy soils. The assembly of bacterial communities was mostly stochastic, with varied dispersion and assembly dynamics across soil types and depths. Network analysis showed that paddy soils had more complicated interspecies relationships than dryland soils, with a greater average clustering coefficient and lower modularity. Drylands had higher biosynthetic and metabolic activity, especially amino acid metabolism and secondary metabolite production, whereas paddy soils had higher energy metabolism. This research emphasizes how land use affects soil physicochemical properties and microbiological populations. Microbial profiles and functional adaptations of dryland and paddy soils provide soil management techniques to optimize soil health and production in diverse agricultural systems.