WOODBUSH GRANITE GRASSLAND (WGG)
The WGG is a declared Critically Endangered ecosystem (1) and at present the most threatened vegetation type in the Limpopo Province (2). WGG occurs on the mountainous Woodbush plateau and shows increased low shrub density on steep south -and east -facing slopes. Trees are mainly absent and their establishment is prevented mainly through frost, fire and grazing (3). However, trees such as Paperbark Thorn (Vachellia sieberiana, previously Acacia sieberiana), Common Spike-Thorn (Gymnosporia buxifolia) and Cabbage Trees (Cussonia spp.) could be seen in a few localised habitats. Several indigenous forest patches also dot the grasslands, but it is the wildflowers that truly steal the show!
Between 1999 and 2007, plant taxonomist Pieter Winter (P.J.D. Winter, unpublished data) recorded around 630 plant species representing 124 families from an area of roughly 240 ha of WGG adjacent to the small town of Haenertsburg. Winter's analysis forms the key reference for the botanical aspects of these grasslands. The present indigenous plant species list stands at 661 species (in 192 ha) of which 18 are Red Listed and 36 are either provincially or nationally protected (4). There are only 53 grass species, while the bulk of the biodiversity is made up of forbs (wildflowers). Geophytes are often abundant and numerous orchid species are currently known to occur within the WGG, all of which are protected by the Limpopo Environmental Management Act of 2003.
Grassland plants are often overlooked, particularly in winter when they die back to survive the frost and fires. Large underground tubers, bulbs and root stocks are typical of grassland plants. These are often highly sought after in the medicinal plant trade and may occur nowhere else. Off-road driving, dumping of rubbish, unplanned fires, excessive fire breaks, removal of top soil, poaching of plants and the uncontrolled spread of alien invasive plants, are all very detrimental to the grasslands and have led to extinctions.
Alien and invasive flora
Several invasive alien plants occur within the WGG. Invasive alien plants are problematic as they affect water supply, encroach on indigenous vegetation and crops, cause very hot fires and increase the risk of soil erosion. Reports also show that, in areas where eucalyptus, wattle and pine are grown, there is an increase in the hydrophobicity of the soil, a state that is difficult to reverse. In other words, these plants lead to water being repelled from the soil.
Some of the most common Alien Invasive Plants (AIPs) that occur in the WGGs and surrounding areas:
To download our brochure, Invasive Alien Plants; A guide to some of the most common alien invasive plants of the Woodbush Granite Grasslands and surrounding areas, click here:
1. National Environmental Management: Biodiversity Act: National list of ecosystems that are threatened and in need of protection, Notice 34809, GN 1002, 9 December 2011.
2. Rouget M, Jonas Z, Cowling RM, Desmet PG, Driver A, Mohamed B, Mucina L, Rutherford MC and Powrie LW 2006. Ecosystem status and protection levels of vegetation types. In: Mucina L and Rutherford MC (Eds) The Vegetation of South Africa, Lesotho and Swaziland. 724–737. Strelitzia 19. South African National Biodiversity Institute, Pretoria, South Africa.
3. Low AB and Rebelo AG (eds) 1996. Vegetation of South Africa, Lesotho and Swaziland. Companion to the vegetation map of South Africa, Lesotho and Swaziland. Dept. of Environmental Affairs and Tourism, Pretoria.
4. Dzerefos CM, Witkowski ETF and Kremer-Köhne S (2017). Aiming for the biodiversity target with the social welfare arrow: Medicinal and other useful plants from a Critically Endangered grassland ecosystem, Limpopo Province, South Africa. International Journal of Sustainable Development and World Ecology 24, 52–64.