was the Grassland Biome, Albany Thicket, Savanna Biome (including the Indian
Ocean Coastal Belt), Nama-Karoo and Succulent Karoo Biomes, which described a
fourfold difference in the proportion of 71 species to which a biome was vulnerable.
Invasion potential of moist grassland and moist savanna vegetation types was
particularly high (>25 of the 71 species).
Trees and shrubs contribute the most invasive alien species in all biomes except
the Nama-Karoo, in which succulent shrubs contribute the most (Fig. 16.2). Succulent shrubs were, however, also well-represented in the Grassland and Savanna
Biomes. These large growth forms may therefore easily transform the host vegetation that is naturally dominated by growth forms of smaller stature, such as grasses or
karroid shrubs. The tall reed Arundo donax (Giant Reed) also transforms riparian
vegetation owing to its greater stature than any native riparian vegetation except
Fig. 16.2 The number of prominent alien plant species in different growth forms that impact on
rangelands in six biomes in South Africa. The upper panel shows species present in riparian
ecosystems, and the lower panel shows those present in dryland areas (away from riparian
ecosystems). The figure is based on the 71 species listed in Table 16.2
472
T. G. O’Connor and B. W. van Wilgen
Ocean Coastal Belt), Nama-Karoo and Succulent Karoo Biomes, which described a
fourfold difference in the proportion of 71 species to which a biome was vulnerable.
Invasion potential of moist grassland and moist savanna vegetation types was
particularly high (>25 of the 71 species).
Trees and shrubs contribute the most invasive alien species in all biomes except
the Nama-Karoo, in which succulent shrubs contribute the most (Fig. 16.2). Succulent shrubs were, however, also well-represented in the Grassland and Savanna
Biomes. These large growth forms may therefore easily transform the host vegetation that is naturally dominated by growth forms of smaller stature, such as grasses or
karroid shrubs. The tall reed Arundo donax (Giant Reed) also transforms riparian
vegetation owing to its greater stature than any native riparian vegetation except
Fig. 16.2 The number of prominent alien plant species in different growth forms that impact on
rangelands in six biomes in South Africa. The upper panel shows species present in riparian
ecosystems, and the lower panel shows those present in dryland areas (away from riparian
ecosystems). The figure is based on the 71 species listed in Table 16.2
472
T. G. O’Connor and B. W. van Wilgen