Consequences of fire and grazing to conservation of arthropod functional diversity in a protected Afrotropical savanna

Abstract

Fires and grazing disrupt the diversity and composition of biological organisms and their functions in the savannas. In the current study, we assessed the impact of fire and grazing intensities on the abundance, species richness and assemblages of eight functional groups of arthropods in Kruger National Park. Pitfalls and active searches were used to collect arthropods at the experimental burnt plots (EBPs) and grazed plots that were undisturbed, minimally or heavily disturbed in Mopane and Skukuza regions. Omnivores constituted the highest proportion (40 %) of individuals, whilst detritivores, granivores, hematophagous, herbivores, nectarivores, predators and scavengers constituted between 0.5 % and 31.4 %. The abundance, species richness and assemblages of different functional groups significantly varied among EBPs and grazed sites in Mopane and Skukuza. The abundance and species richness of arthropods were higher at EBPs compared to grazed plots in Mopane and Skukuza. Furthermore, abundance was higher at the undisturbed compared to disturbed plots and a contrary pattern was observed for species richness. Results showed a distinct variation in the assemblage of detritivores, nectarivores, omnivores and predators between EBPs and grazed plots, with a clear separation between Mopane and Skukuza. However, the composition of granivores and herbivores was neither influenced by fires nor grazing in the Mopane and Skukuza. The intensity of disturbances by fire and grazing failed to drive arthropod assemblages within different functional groups. We conclude that fire and grazing are potent drivers of assemblages of arthropod functional groups in Afrotropical savannas requiring evidence-based manipulation for the conservation of key species.