Study area
The study was performed in the Kruger National Park (KNP), located in the Limpopo and Mpumalanga Provinces in north-eastern South Africa. It extends 360 km from north to south and 65 km from east to west and covers almost 20,000 km2, which makes it one of the largest protected areas in Africa. The park has seven perennial rivers: Sabie, Olifants, Crocodile, Letaba, Shingwedzi, Luvuvhu, and Limpopo, which flow from west to east (du Toit et al. 2003). The park has variable environmental conditions; altitude ranges between 140–780 m a.s.l, and annual precipitation between 450–750 mm. Bedrock is mainly acidic and nutrient-poor in the western half of the park (granitoids), and alkalic and more nutrient-rich in the east (mostly basalts). Grasses are represented by ~230 species in the KNP (Gertenbach 1983), ranging from a short pioneer species of low nutritional value, such as Aristida spp. orPogonarthria squarrosa to tall species of a high nutritious value, such as Panicum maximum , Digitaria eriantha orThemeda triandra. There are 19 vegetation types in KNP based on a phytosociological classification (Mucina and Rutherford 2006), of which 13 were covered by our plots; most represented were SVl3 Granite Lowveld (13 plots), SVmp4 Mopane Basalt Shrubland (12 plots), SVl5 Tshokwane-Hlane Basalt Lowveld (10 plots), and SVmp5 Tsende Mopaneveld (nine plots; Hejda et al. 2022). The average cover of woody and grass species was 45% and 31%, respectively (see Hejda et al. 2022 for further details on vegetation cover and plant community composition).