Herbaceous vegetation changes along a bush encroachment intensity gradient in a montane area

Abstract

AbstractAlthough bush encroachment in rangelands is a widely reported phenomenon, particularly in the arid and semi‐arid regions of southern Africa, the knowledge of the impact of bush encroachment in montane rangelands is inadequate to support the sustainable management of these important ecosystems. This study assessed how herbaceous vegetation changes along a bush encroachment intensity gradient in the montane rangelands of Sehlabathebe in the Qacha's Nek District of Lesotho. Fifty 16 m2 vegetation plots were randomly selected on a bush‐encroached rangeland area. In each plot, bush species data, including canopy cover, richness, density and height, were recorded. The Braun‐Blanquet method was used to assess herbaceous vegetation. The data were analysed using regression analysis, correlation analysis and ordination. Forb and graminoids attributes (Shannon‐Wiener diversity, species richness, evenness and percentage cover) together with bush attributes (height, density, diversity, evenness, richness and cover %) were subjected to regression and ordination. Results revealed that bush cover was negatively correlated with both forb and graminoids vegetation cover. While forb species richness, evenness and Shannon‐Wiener diversity increased with an increase in bush encroachment intensity, graminoid species abundance and diversity decreased. Overall, bush encroachment negatively impacted the structure and composition of graminoids. This implies that bush encroachment compromises the condition of montane rangelands because graminoids contribute to grazable forage more than forbs in these montane ecosystems.