**4.4. Wetland communities**

Wetland communities in which *V. karroo* is usually encountered are found in KwaZulu-Natal, Mpumalanga and Limpopo Province. Although these communities occur in both the Savanna and Grassland Biomes, we regard them as a distinct vegetation type because of their unique species composition. This vegetation type differs from the riparian thickets, which are mainly associated with clayey soils along rivers and streams. The wetland communities described here are generally associated with moist sandy soils and are dominated by grasses and forbs. *V. karroo* in these communities is the only notable woody species (**Figure 12**) but is not as prominent as in the riparian thickets.

Some of the major communities recognised within this vegetation type are as follows: The first is the *Hemarthria altissima* Class described by Du Preez and Bredenkamp [76] for the southern and eastern Free State. It represents vegetation of moist soils on marshes, streambanks, riverbanks, dam edges, and vleis (shallow, seasonal wetlands). Although *V. karroo* is not present in communities described by Du Preez and Bredenkamp [76], it can be encountered in other wetland communities regarded as part of this class, namely those of the central-northern KwaZulu-Natal described by Eckhardt et al. [82]. The other distinct community is the *Fuirena pubescens–Schoenoplectus corymbosus* wetland vegetation described by Siebert et al*.* [61]. This wetland vegetation is found throughout the Sekhukhune Centre of Plant Endemism in Limpopo and Mpumalanga Provinces. It occurs on stream banks in valleys, in seepage areas on mountain slopes and also in wetlands on the mountain plateaus. It is associated with wet, vertic black clay soils. The main distinction between this vegetation and other *Vachellia karroo*-dominated riparian thickets is the absence of woody species such as *Ziziphus mucronata, Diospyros lycioides,* and *Rhus pyroides*, which are the usual companions of *Vachellia karroo* along the riverbanks. The wetland communities where *V. karroo* occurs are listed in **Table 5**.

#### **4.5. Nama-Karoo communities**

**Figure 11.** Riparian vegetation along the Modder River near Glen (top, middle) and Sand River near Ventersburg

(bottom), Free State Province, South Africa (photos: M. Dingaan).

130 Pure and Applied Biogeography

The Nama-Karoo biome is the second-largest biome in South Africa, covering 28.35% of the country [57]. It occurs on the western half of South Africa, at altitudes ranging from 500 to 2000 m but most of the biome falls between 1000 and 1400 m [56, 57]. This is an arid biome, characterised by unreliable summer rain that varies between 100 and 520 mm per year [85]. The topography resembles extensive, flat to undulating plains dotted with hills and occasional mountains [57]. The dominant vegetation is a grassy, dwarf shrubland (**Figure 13**), comprising a mix of low shrubs, grasses, succulents, geophytes and annual herbs [56, 85]. The annuals on average comprise the highest number of species in the biome [86].

*V. karroo* in this karroid vegetation is found in southern Free State and some areas in the Eastern Cape. The vegetation is found in varied habitats, ranging from gentle slopes

**Figure 12.** Wetlands near Verkeerdevlei (top), Winburg (middle) and Ventersburg (bottom), Free State Province, South Africa (photos: M. Dingaan).


**Table 5.** Classification and habitat features of wetland communities.

**Figure 12.** Wetlands near Verkeerdevlei (top), Winburg (middle) and Ventersburg (bottom), Free State Province, South

Africa (photos: M. Dingaan).

132 Pure and Applied Biogeography

and plateaus in south-western Free State to rocky habitats on hot and dry slopes in the Eastern Cape. The presence of *V. karroo* in these karroid veld types can be ascribed to bush encroachment occurring as a result of overgrazing [27]. The plant communities where *V. karroo* occurs are part of the *Acacia (Vachellia) karroo* Class proposed and described in detail by Dingaan [54].

**Figure 13.** Nama-Karoo at Augrabies National Park (top, middle) and in Hopetown (bottom), Northern Cape Province, South Africa (photos: M. Dingaan).
