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In savannas, ruminant herbivores can have divergent impacts on tree recruitment and subsequent woody cover. Whereas heavy grazing by cattle results in woody thickening, intensive grazing by wildlife instead tends to be associated with lower woody cover.To disentangle why woody cover is low in areas heavily grazed by wildlife, we investigated (a) whether grazing lawns attract indigenous mammalian browsers, and if a preference for short‐grass habitat decreases with browser body mass as predator susceptibility decreases; and (b) whether browser attraction to grazing lawns translates into the suppression of woody plants, including seedlings and saplings, thus maintaining the openness of heavily grazed short‐grass areas.In Kruger National Park, South Africa, we contrasted browser abundance (using dung counts) on grazing lawns and on low‐herbivory sites characterised by tall grass. Additionally, a herbivore exclosure experiment was set up to investigate the combined impact of browser removal and grass height habitat type on seedling survival and sapling growth of a dominant woody plant species. Finally, in Hluhluwe‐iMfolozi Park (HiP), we examined the long‐term (10 years) impact of browser removal on the growth rates of a range of woody species, monitored across ten sites along a gradient of herbivory ranging from grazing lawn to tall grass.Steenbok and impala selected short‐ over tall grass as preferred browsing sites, while elephant preferred tall grass. Browser abundance on short grass decreased with browser body mass, indicating that predator avoidance might be a key factor driving mesoherbivores to utilise grazing lawns.Seedling survival was lowest on grazing lawns when browsers were present, with mortality occurring in two out of every three seedlings. Similarly, sapling growth was lowest on grazing lawns, although browser removal had no significant effect. Evidence for increased browser impact on grazing lawns was clearest from our long‐term herbivore exclosure experiment in HiP, which demonstrated that browsers strongly modify the growth rates of woody plants in short‐grass habitats.Synthesis. These results provide support for the hypothesis that browsers, particularly browsing mesoherbivores and mixed feeders, are attracted to short‐grass habitats, and that they help maintain grazing lawn openness by suppressing seedling survival and woody plant growth where grass is kept short by grazers. [ABSTRACT FROM AUTHOR]

Grazing lawn and flammable-tussock grass communities are contrasting resource pools for mammalian grazers in terms of forage quantity and quality. Drought events fundamentally alter forage availability within these communities and therefore should alter herbivore use with repercussions for the recovery and functioning of ecosystems after drought. During and after an intense El Niño drought (2014–2017) in Kruger National Park, South Africa, we addressed two questions: (1) how does herbivore use of different grass types change during a drought and (2) how do these changes affect grass productivity post-drought? We monitored grazer use of three different grass communities (lawn, tussock and burned-tussock) at a landscape scale and measured primary productivity monthly during and post-drought. For the first drought year, grazer numbers were highest on grazing lawn communities. This pattern continued into the second dry growing season, until herbivores finally left the study area. Both lawns and tussock grasslands recovered rapidly after the first good rainfall (productivity > 150 g m−2 per month). However, grazers did not return to feed on the same patches they had frequented pre-drought resulting in grazing lawn grasses self-shading and senescing. Longer droughts have the potential to decouple grazers and grazing lawns with negative impacts on lawn productivity and persistence that could drive the loss of lawns in savanna landscapes and impact mesoherbivore populations. It is clear from our results that grazer effects need to be incorporated into drought frameworks to understand the consequences of droughts for grassland function. [ABSTRACT FROM AUTHOR]

Fire and herbivory are competitive processes in grassy ecosystems as they both consume above‐ground biomass. Despite this interaction between fire and grazing, herbivore and fire management plans in conservation areas are usually perceived, and hence managed, independently. This study aims to demonstrate the importance of acknowledging and integrating the interdependence between herbivore and fire management.We compare average proportional area burnt during years when large‐scale culling kept herbivore biomass within a narrow range within the Kruger National Park, South Africa, against subsequent years of no culling when herbivore densities increased to effectively double the biomass. Furthermore, to improve our mechanistic understanding, we utilize natural gradients in rainfall (north to south) and grazing (distance from rivers) to test a conceptual model of how herbivory influences fire occurrence under different rainfall regimes.Fires were more prevalent during the culling period than thereafter, and the fire suppression effect of increasing grazing biomass was most pronounced in areas closer to rivers (50% reduction within 1 km of rivers).The "grazer effect" (i.e. difference between % area burnt between low and high grazer biomass years) seems to be more pronounced in arid landscapes than in semiarid landscapes, which in turn is more pronounced than in the mesic landscapes.Despite elephants being mixed feeders, elephant density influences fire occurrence more than the density of buffaloes or hippopotami.Synthesis and applications: Herbivore and fire management actions should be integrated, as events that influence herbivore densities go on to influence fire occurrence in subsequent years. In areas with 400–600 mm MAP it is particularly important because changes in herbivore numbers—due to drought, predation, disease, or human interventions—can result in switches between fire‐ and herbivore‐dominated systems, with cascading consequences for biodiversity and ecosystem function. Furthermore, grazing gradients (in this case distance to closest perennial river) are critical as it allows both fire and herbivore‐dominated systems to occur within the same system along the gradient. This increases management possibilities, as management actions that induce grazing gradients can have positive implications for maintaining biodiversity in protected areas. Herbivore and fire management actions should be integrated, as events that influence herbivore densities go on to influence fire occurrence in subsequent years. In areas with 400–600 mm MAP it is particularly important because changes in herbivore numbers—due to drought, predation, disease, or human interventions—can result in switches between fire‐ and herbivore‐dominated systems, with cascading consequences for biodiversity and ecosystem function. Furthermore, grazing gradients (in this case distance to closest perennial river) are critical as it allows both fire and herbivore‐dominated systems to occur within the same system along the gradient. This increases management possibilities, as management actions that induce grazing gradients can have positive implications for maintaining biodiversity in protected areas. [ABSTRACT FROM AUTHOR]