Soil Biodiversity of Eucalyptus saligna : Insights Into Bacterial and Nematode Communities

ABSTRACT Soil microorganisms and nematodes are key regulators of soil function, yet their co‐occurrence in Eucalyptus rhizospheres remains poorly understood. In this exploratory study, we characterised bacterial and nematode communities associated with Eucalyptus saligna soils in Limpopo, South Africa, using high‐throughput 16S rRNA gene sequencing and nematode surveys. Bacterial assemblages were dominated by Proteobacteria (42%), Acidobacteria (28%), Actinobacteria (12%) and Planctomycetes (9%). Eleven bacterial genera occurred across all sites, with Rhizobiales (prominence value, PV = 315,350) and Xanthobacteraceae (PV = 292,930) emerging as the most prominent taxa. Nematode surveys identified 19 genera, including plant‐parasitic such as Meloidogyne (PV = 5759.1) and abundant free‐living such as Tylolaimorphus (PV = 4150.0) and Acrobeloides (PV = 2900.0). Principal component analysis showed that bacterial communities were associated with soil pH, salinity and nitrogen forms, whereas nematode assemblages were associated with phosphate and sand content, together explaining 83%–90% of total variance. Network analysis indicated that all sampling sites functioned as central hubs (degree = 19–23; eigenvector centrality = 0.90–1.0), integrating nematode–bacteria associations. Key connector taxa included Acrobeloides , Wilsonema and Aphelenchoides, as well as bacteria such as Rhizobiales and Acidothermus . These findings provide a baseline framework for understanding belowground biodiversity and co‐occurrence patterns in Eucalyptus plantation soils.