Thornwood is surrounded by four different ecosystems: sand forest, grasslands, wetland and thorn scrub. Today we are going to learn about the rarest of them all, sand forest.
Sand forest covers a smaller area than any other forest types in South Africa. It is extremely rare and vitally important and thus protected.
Very few studies have been carried out on the sand forests. Those that have been conducted, the majority of the research has been on the plant diversity within these forests.
Sand forests grow on ancient sand dunes in northern KwaZulu-Natal and southern Mozambique. In South Africa these forests are known simply as Sand Forest, while in Mozambique they are known as Licuati Forest.
Sand forests are thought to be relics of coastal dune forests, which have been separated from the ocean for more than a million years as the shoreline has shifted slowly eastwards over the millennia.
There are indications that sand forest has allelopathic effects which may bring about this zone of inhibition and this aids in limiting fires spreading from the neighbouring savannah into the forest; creating a unique environment for itself.
Sand forests have a thick humus layer due to the extremely low decomposition rates. Some sandy forests have even been recorded to have more than a meter of leaf litter on top of the white sand. Multiple reasons exist as to why there is such a large accumulation of organic matter including high acidity of the soil, high content of toxic compounds in the litter, and low nutrient quality of the litter.
Sand forests are well known for their unique biodiversity. To date there have been more than 2,500 species of vascular plants and of those, 230 species are endemic within the Maputaland region. Distinct sclerophylly, or vegetation with thickened, hardened foliage that slows moisture loss, is a characteristic of a vast number of the plants found in this region.
Unique trees include Lebombo wattle (Newtonia hildebrandtii), red-heart tree (Hymenocardia ulmoides), lavender-leaved croton (Croton pseudopulchellus) and stink bushwillow (Pteleopsis myrtifolia).
Due to nutrient and water restrictions, the vegetation that grows in the sand forests is very specialized. Many of the trees and shrubs have evolved anti-herbivorous defenses. Herbivores seemed to favour vegetation of plants in clay soils over the white sandy soils. In no presence of herbivores however, the clay soil vegetation survived just as well as in white sand, but grew much taller and produced more leaf area.
What animals will you find in Kuleni’s sand forest? Duiker, suni, snakes and an array of interesting insects!
If you would like to learn more about sand forest, Hluhluwe’s own, Dr Francois du Randt, has published a book entitled ‘The Sand Forest of Maputaland’. There are 400 pages of beautifully photographed and detailed information on a wide range of topics relating to the sand forest, from vegetation to animals, butterflies and insects.