Effects of prescribed burning and mechanical bush clearing on ungulate space use in an African savannah

Abstract

Savannah ecosystems exhibit constant transitions between states dominated by trees and states dominated by a combination of trees and grasses. Transitions between these states are driven by interactions between fire and herbivory. Bush encroachment (i.e. an increase in the density of woody vegetation) is often caused by anthropogenic disturbance such as climate change, invasive plants, fire control and livestock practices. Since bush encroachment alters the dynamics between fire and herbivory, it may have significant impact on savannah ecosystems. Two of the most common measures to mitigate bush encroachment are prescribed burning and bush clearing by mechanical treatments. We studied the effects of these two mitigation measures on ungulate space use in Lapalala Wilderness, a private conservation area within the Waterberg Biosphere Reserve, northern South Africa. Burning and bush clearing affected both the overall abundance and the species composition of ungulates at particular patches, but these effects were influenced by habitat and the type of bush clearing treatment. Contrary to our expectations, most species occurred less frequently in burnt patches, and also less frequently in patches that had been bush cleared. Our results suggest that combined effects of fire and bush clearing may have positive effects on grazers and negative effects on browsers. Although our sampling design did not allow us to fully resolve interactive effects of burning and bush clearing treatments across habitats, our study highlights the fact that there are complex ecological consequences of habitat alterations in savannah ecosystems.