Supplementary material from "Impact of Seriphium plumosum densification on Mesic Highveld Grassland biodiversity in South Africa"

Mesic Highveld Grassland is important for biodiversity conservation, but is threatened by bush densification from Seriphium plumosum. This indigenous densifier spreads rapidly and outcompetes other herbaceous species, changing the species composition and structure of grasslands. This study looks at three different densities of S. plumosum and how these affect grassland biodiversity within Telperion, Mpumalanga, South Africa. An intermediate density of S. plumosum (1500 ind ha⁻¹) resulted in the highest plant species diversity (H = 2.26), a low density (24 ind ha⁻¹) was moderately diverse (H = 1.96) and a high density (9500 ind ha⁻¹) was least diverse (H = 1.78). There were differences between the three densities in terms of plant species diversity, with the intermediate density being significantly more diverse (p < 0.01) than both the low and high densities. Findings indicate that there was a significant difference between the sites in terms of ecological successional status (p < 0.01). The presence of S. plumosum at low densities can be considered an integral part of the environment. It is important that in areas where S. plumosum occurs, it should be monitored. If this species is not in balance within its environment and it starts becoming dense, it will negatively affect the biodiversity, species composition and structure of the habitat.