Quantifying the effect of chemical bush control of Senegalia mellifera on vegetation production in the Eastern Kalahari Bushveld, South Africa

Abstract

Bush encroachment is the invasion of whole landscapes by indigenous and alien woody species. An imbalance in the ratio of grasses to bushes is a consequence of bush encroachment due to competition for moisture, nutrients and sunlight. This imbalance results in a decrease in grass cover, plant biodiversity and grazing capacity, leading to severe economic losses. Several methods exist to reduce high woody plant densities, including mechanical, manual, biological or chemical control. In this study, we assessed the structural and compositional attributes of the grass layer and compared these to the woody vegetation structure for herbicide-controlled rangelands and the no chemical control. The main objective was to evaluate the potential of chemical control to restore an open savanna system dominated by perennial grasses. Woody-dominated vegetation resulting from long-term overgrazing was assessed and compared to chemically controlled sites. Results revealed that chemical control treatment increased forage production and maintained woody-patch conservation. After the treatment, the sites were characterised by more productive and desirable woody species. The re-encroachment of woody species at all bush-controlled sites is possible. A follow-up control programme to manage and mitigate encroachment needs to be implemented when mitigating bush encroachment.