Six-hundred-and-fifty plant species from 280 genera and 85 families have been recorded as indigenous to the Bontebok National Park (BNP), which lies 5 km south of Swellendam, in the Western Cape. Twenty-nine of these plant species are globally threatened with extinction and another 23 are species of conservation concern. Three species (Aspalathus burchelliana, Diosma fallax, Erica filamentosa) are endemic to the park. The Asteraceae, Iridaceae and Fabaceae ranked high as speciose families, in line with the Cape Floristic Region (CFR) as a whole, while the Asphodelaceae, Crassulaceae, Poaceae and Cyperaceae were overrepresented, and the Rutaceae, Proteaceae and Ericaceae underrepresented at BNP. The largest genera were Aspalathus (19 species), Crassula (17), Pelargonium (16), Erica (15), Oxalis (12), Moraea (11), Helichrysum (10) and Hermannia (10). Geophytes were the dominant growth form (23% of species recorded), followed by dwarf shrubs (20%), herbs (16%), graminoids (15%), shrubs (13%), succulents (8%), trees (3%) and climbers (2%). Forty alien plant species were recorded (likely an underestimate of true numbers) with the Poaceae most speciose and arguably the biggest invasive threat at the park. With 20 plant species/km2 , the flora of BNP is richer than expected based on its location within the south-eastern CFR. Similarity with floras of other lowland and montane protected areas in the region is low (b33% and b20% respectively), demonstrating that a large component of BNP’s flora is not conserved elsewhere. Within a landscape context, BNP forms part of a cluster of connected core sites for Renosterveld conservation. This work confirms the high importance of BNP for flora conservation nationally and even globally.
The Bontebok National Park (BNP) is a small (3435 ha) protected area, originally established to conserve one of the rarest antelope in Africa, the bontebok (Damaliscus pygargus pygargus; Red listed as Vulnerable) (Friedmann and Daly, 2004; Skinner and Chimimba, 2005). However, BNP is also located within the internationally renowned hotspot of biodiversity, the Cape Floristic Region (CFR) (Goldblatt and Manning, 2002; Myers, 1990) and conservation of the vegetation in the park has over time become an increasing priority owing to near-complete habitat destruction outside the park (Von Hase et al., 2003). There is uncertainty around whether the vegetation of BNP represents ‘true’ Renosterveld which generally occurs on shales or granites, or is rather a type of lowland Alluvium Fynbos on old boulder terraces (Rebelo, 1992; Theron, 1967). Accordingly, the national vegetation map of South Africa classified the vegetation of BNP as Swellendam Silcrete Fynbos, considering it a poorly known vegetation type exhibiting floristic features of both Fynbos and Renosterveld (Rebelo et al., 2006). Structurally it is described as a medium-tall evergreen shrubland or grassland, with predominantly asteraceous Fynbos, but graminoid Fynbos occurring on summits and northern slopes where disturbed. The national status of Swellendam Silcrete Fynbos is Endangered and it has a conservation target of 30% meaning that N30% of the original extent of this vegetation type needs be protected in order to capture 75% of the species occurring in it. Only 4% is statutorily conserved, largely in BNP, whereas 43% is already transformed (Rouget et al., 2004), largely through cultivation and afforestation with commercial pine plantations (Rebelo et al., 2006). Small areas of Cape Lowland Alluvial Vegetation (Mucina et al., 2006) furthermore occur within the park associated with the Breede River and its tributaries. This vegetation type is Critically Endangered as 69% is transformed and only 1% statutorily conserved (Rouget et al., 2004).
At the regional scale, the conservation plan for the Cape Lowlands Renosterveld (Von Hase et al., 2003) mapped the southern half of the park as Renosterveld. BNP is also included in the regional map of the Riversdale Plain, where Vlok and De Villiers (2007) recognised five different vegetation types within the park, i.e. Proteoid Fynbos, Asteraceous Fynbos, Inland Pans and two types of River/Floodplain vegetation along the Breede River. At park scale, the only published account of the flora (Grobler and Marais, 1967) comprises a basic description and associated map of the vegetation communities of less than half the area of the current park. These authors identified 12 vegetation communities belonging to three main vegetation types, i.e. riparian/tree type, sweet veld/renosterbos type (Acocks, 1988; Veld Type 46), and mixed grass veld/Leucadendron type (Acocks Veld Type 70). Luyt (2005) subsequently mapped the vegetation of BNP, although a detailed vegetation account or plant species inventory was not the focus of his study.
Despite the rudimentary vegetation descriptions, a comprehensive plant species inventory was kept (SANParks unpubl. data) throughout BNP’s history along with a park-based herbarium collection to which various botanists contributed. Kruger et al. (1989, cited in Richardson et al., 1992) reported 20 years ago that BNP had 446 native plant species. This figure is likely based on the former National Botanical Institute’s unpublished data (cf. Taylor, 1972).
Various factors may affect vegetation structure and composition, including management practises. At BNP, these are fire and grazing. Fynbos and Renosterveld are both fire-prone and fire-
adapted vegetation types. The frequency, season, intensity and size of fires are primary determinants of plant species composition, structure and successional patterns (Kruger and Bigalke, 1984; Van Wilgen et al., 1992). Frequent burning and/or overgrazing are thought to convert Swellendam Silcrete Fynbos to Grassy Fynbos on northern slopes and to a species-poor Renosterveld elsewhere (Rebelo et al., 2006). BNP has a history of frequent burning in some areas of the park (Kraaij, 2010) in combination with relatively constant, and at times, heavy utilisation by large grazing ungulates (Kraaij and Novellie, 2010), both of which may have impacted on the structure and composition of the vegetation.
The aim of this work is to provide an updated checklist of the plant species of BNP to act as a basic reference for future floristic and ecological work in the region. The composition of the flora is furthermore assessed in terms of dominant families, genera, growth forms, CFR-endemism and species richness, and put into perspective with other protected areas in the region, and the CFR in general.