NEWS
Through Thicket and Thin : Protecting This Incredible Biome
Zoë Chapman Poulsen
Current Address : Botanical Society of South Africa Reprinted from : https :// bit . ly / 3OqLjlW
South Africa ’ s thicket vegetation is characterised by a dense tangle of multistemmed and often prickly shrubs . Despite its initially unwelcoming appearance , it is in fact home to the highest diversity of different plant growth forms compared with the country ’ s other biomes .
Thicket comprises evergreen and deciduous trees , a rich succulent diversity from towering Euphorbias to creeping vygies , shrubs , vines , bulbs and grasses . Historically , thickets have received little attention from scientists in comparison with other biomes such as the fynbos , but this is changing .
Where is thicket found ? Thicket is found in semi-arid areas of the
Western Cape and the Eastern Cape . It forms part of the thicket biome and is present as a key vegetation type in three different biodiversity hotspots in South Africa , namely the Maputaland- Pondoland-Albany , Succulent Karoo and Cape Floristic Region .
It is distributed in South Africa from the Gouritz River eastwards to the Kei River , with the largest areas of thicket being found in the Gamtoos , Sundays and Fish River valleys .
Thicket biodiversity
There are estimated to be around more than 1 500 plant species that are found in thicket , of which about 20 % are endemic to this extraordinary vegetation and found nowhere else on earth .
Thicket is also home to the second largest succulent flora in the world , with 344 species and an extraordinary level of endemism of 50 %.
It comprises a total of 206 species across 66 genera . But thicket vegetation is highly understudied and it ’ s likely that there are in fact more species waiting to be discovered . Either way , the proportion of bulbs in the total thicket flora is one of the highest in the world , only short of the fynbos biome and Namaqualand in the Succulent Karoo .
Thicket is also home to many different animals and birds , as well as a substantial reptile fauna including four tortoise species and many endemic lizards . Large mammals play an important ecosystem engineering role ,
Figure 1 . Top : Dune Thicket along the Eastern Cape coast , with African Aloe ( Aloe africana ) emerging above the thicket canopy . Left : Grassridge Bontveld , a mosaic-type thicket restricted to calcareous soils derived from limestone . Right : Many shrubs typical of karoo shrublands also occur in arid forms of thicket , such as this Perdekaroo ( Oedera humilis ) found in noorsveld around Jansenville . Dunes along the Cape south coast house dune fynbos – thicket mosaic vegetation , with dune thicket patches restricted to deep , fire-protected swales . Photos by Adriaan Grobler .
Figure 2 . Succulent-rich Valley Thicket on shallow soils of the Zuurberg Mountains near Kirkwood . Photo by Adriaan Grobler .
Grassroots Vol 22 No 2 July 2022 32