NEWS including elephants , black rhinos and even buffalo , creating open spaces that allow other wildlife to move through the vegetation .
Formed by the climate
Subtropical thicket vegetation is found in areas that receive an average annual rainfall of 200 – 950 mm per year .
This rainfall is distributed throughout the year due to the convergence of two different climatic systems . The region to the southwest receives year-round rainfall , whereas the area to the northeast receives most of its rainfall during the summer months .
In the northeast of the thicket biome , as the climate moves toward summer rainfall , the vegetation gradually transitions to grassland and thorn tree savanna . As the climate changes to the southwest , there is a gradual transition to fynbos .
Geology and soils : A rich history
The thicket biome is dominated by the mountains of the Cape Fold Belt , which comprises sandstone and quartzite geology of the Table Mountain and Witteberg groups .
Figure 3 . Top left : Greater Kudu ( Tragelaphus strepsiceros ) are a common sight in Thicket vegetation of the Eastern Cape . Top right : The succulent shrub Crassula perfoliata var . falcata grows on open rocky slopes in Thicket vegetation . Bottom left : Club Spurge ( Euphorbia clava ), a stem-succulent frequently seen along the fringes of thicket clumps . Bottom right : The dwarf succulent Aloe bowiea is an unusual and threatened aloe species found only in open patches between Thicket in Nelson Mandela Bay . Photos by Adriaan Grobler .
These date from the Ordovician Period ( starting 485 million years ago ) to the Silurian Period ( from 443 million years ago ) and the Devonian Period ( between 419 to 358 million years ago ).
This geology is of biogeographical importance because it supports outliers of fynbos and renosterveld vegetation within the thicket biome .
Most of these fine-scale variations in vegetation are because of the interaction between climate and soils , the latter of which are derived from the underlying geology .
Origins of the thicket biome
Most lineages of the flora and associated insects of the thicket biome have their origins in the Eocene ( 56 – 33.9 million years BP ) when the climate became much colder and drier . This timing is supported by evidence derived from fossil pollen .
Figure 4 . Top left : Shepherds Tree ( Boscia oleoides ) in arid thicket that has been degraded by livestock overbrowsing . Top right : Above : Noorsveld , a form of Arid Thicket , with karroid elements like soetnoors ( Euphorbia radyeri ) and Cape Aloe ( Aloe ferox ). Photos supplied by Adriaan Grobler .
Some taxa have their origins in the supercontinent of Gondwanaland , dating back more than 280 million years . This includes cycads in the genus Encephalartos , the cabbage tree Cussonia in the Araliaceae family , as well as the bird of paradise plants ( Strelitzia ).
Many of the trees that grow in thicket are tropical in affinity , with extensive distribution ranges extending northwards
33 Grassroots Vol 22 No 2 July 2022