Climate-driven patterns of functional structure of nematode communities along Limpopo grasslands, South Africa

Soil nematode communities are valuable indicators of ecosystem functioning and soil food-web structure. This study assessed nematode diversity, trophic composition, and ecological organization across four grassland sites in Limpopo Province, South Africa: Dalmada (D), Haenertsburg-top (H1), Haenertsburg-down (H2), and Sovenga Hills (S). A total of 34 nematode genera were identified, representing herbivores, fungivores, bacterivores, predators, and omnivores. Bacterivores were the most taxonomically diverse and numerically dominant trophic group. The c–p spectrum ranged from 1 to 5, with c–p 2 taxa dominating H1 and H2. Maturity and Shannon diversity were highest in H1 and D, respectively, while Enrichment Index values were highest in S and D; the Structure Index was lowest in H2 (0). nMDS and RDA revealed distinct site-related patterns associated with soil physicochemical gradients. Piecewise structural equation modelling showed that sand was negatively associated with bacterivores (β = − 0.419, p = 0.0408), whereas clay was positively associated with omnivores/predators (β = 0.658, p = 0.0333). Bacterivores were positively associated with herbivores (β = 0.319, p = 0.0053) and omnivores/predators (β = 0.358, p = 0.0045). In conclusion, nematode community structure and soil food-web characteristics varied among grassland sites, reflecting differences in local soil physicochemical conditions and broader environmental gradients.