Understanding how biodiversity responds to fine-scale heterogeneity improves our ability to predict larger-scale diversity patterns and informs local-scale conservation practices. This information is important in the design of conservation set-asides in commercial forestry landscapes in the Maputaland-Pondoland-Albany biodiversity hotspot, in South Africa. We assessed how soil arthropod assemblages vary among biotopes with varying degrees of contrast in forestry landscape mosaics in this hotspot. The biotopes included dry and hydromorphic grasslands, indigenous forests and pine plantations. Assemblages were highly segregated among all biotopes for overall arthropods, and for all the feeding guilds, namely predators, herbivores, detritivores, and omnivores. There was a high degree of assemblage dissimilarity between structurally contrasting biotopes (grasslands vs. wooded biotopes) and biotopes that differ in their degree of transformation (natural biotopes vs. plantations). Yet, there was an equally high level of assemblage dissimilarity between dry and hydromorphic grasslands, which are similar in structure and undergo the same disturbance regimes, which emphasises the responsiveness of soil fauna to fine-scale habitat heterogeneity. Different biotopes favoured different feeding guilds and each biotope had species strongly associated with it, highlighting the complementarity of the biotopes. All natural biotopes had relatively high species richness, diversity, and species turnover. The diversity and turnover in pine plantations was as high as in the natural areas, suggesting that plantation conditions may favour certain soil arthropods. Implications for insect conservation Current delineation of conservation areas in timber estates that prioritize biodiversity-rich dry grasslands, wetlands and indigenous forests, greatly benefit soil arthropods. Approaches that promote a mix of biotopes in conservation areas and having biotopes represented across different landscapes would further maximize local heterogeneity and landscape-scale soil arthropod biodiversity.