Microbial Diversity of Selected Malaysian Dipterocarp Rhizosphere Soil

The Dipterocarpaceae family, comprising nearly 700 species across 16 genera, is a dominant component of Southeast Asian tropical rainforest and plays a critical ecological and economical role. In Malaysia, dipterocarps are widely distributed and serve as one of the essential tree families in the forest ecosystems. Their rhizosphere represents a unique microhabitat where complex interactions between root, soils and microbial communities occur. However, there aren't enough datasets on microbial diversity of Malaysian dipterocarp rhizosphere soil to be exploited for sustainable forest conservation and agriculture effort. This study aimed to unravel the microbial diversity of selected dipterocarp species (Dipterocarpus oblongifolius, Neobalanocarpus heimii, Shorea sumatrana and Dryobalanops aromatica) across three environmentally different sites; the FRIM Dipterocarp Arboretum, Valencia (township) and Wetland Arboretum Centre (nursery), using 16s and 18s amplicon nanopore sequencing. Dipterocarp rhizosphere soil across the three sites were acidic (pH 3.62-5.06). FRIM exhibits the highest soil moisture and organic matter content, significantly higher than Valencia and WAC. Valencia showed high potassium ion, nitrate, As and Mn concentration, while WAC had the lowest NO3 but significantly higher Cr and Fe concentration. Site-specific differences were statistically significant (p < 0.05) for most parameters. Bacteria communities were dominated by Proteobacteria across all sites, with WAC showing significantly higher bacterial diversity (Shannon index). Valencia exhibited higher relative abundance of Firmincutes and Desulfobacterota, while FRIM showed elevated Firmicutes levels. Eukaryotic communities were primarily fungal, dominated by Basidiomycota and Ascomycota, with WAC showing significantly higher eukaryotes diversity (Shannon index). FRIM showed significantly higher Basidiomycota abundance while WAC and Valencia had elevated Ascomycota. Beta diversity analysis revealed distinct clustering patterns, with WAC harbouring the most unique community structures for both bacteria (R2 = 0.176) and eukaryotes (R2 = 0.300). LEFSE a analysis identified key bacterial and fungal biomarker phyla: Proteobacteria for WAC, Firmicutes for FRIM, Planctomycetota for Valencia, Ascomycota for WAC, Basidiomycota for FRIM and Cryptomycota for Valencia. The CCA plot demonstrated significant correlations between microbial diversity and soil physicochemical properties, particularly soil moisture, pH and heavy metal concentration, indicating site-specific environmental influence of dipterocarp rhizosphere soil microbiomes.