Clearing for cropland and overgrazing by livestock (mostly goats) has stripped the  vegetation in vast areas of the thicket biome, especially in very sensitive dry areas. This has turned lush, carbon and moisture rich ecoystems into dry, barren wastelands, where topsoil has been lost, and erosion is widespread, with massive effects on the water storage capacity of catchment areas. In degraded thicket, most of the rainfall does not seep into the soil, and rapidly runs downslope, taking much of the soil with it. The exposed soil surfaces then rapidly lose any absorbed water as soon as the sun comes back out, and this is a major contributor to the dire state of the Eastern Cape's water supply. To restore vegetation cover in these areas will slow down runoff and erosion, and increase infiltration when it rains, and thus improve stream flow and improve water security.

Spekboom (scientific name: Portulacaria afra) is a large succulent shrub (sometimes taller than 4 metres) found in dry areas of the thicket biome. It is extremely tolerant to drought, and grows remarkably fast in very dry areas, absorbing far more carbon dioxide than other plants found growing alongside it. It is considered an ecosystem engineer because of its rapid growth rates and the variety of beneficial effects it has in these dry areas. Particularly, it's dense and sprawling growth form, and it's production of a thick layer of leaf litter enriches the soil, providing a cool, shaded, and moist microclimates that are crucial for the germination and establishment of  many other thicket tree species. Without spekboom, most of these tree species would probably not be found in these very dry areas, such as the Baviaanskloof, where rainfall is sporadic and ungenerous. As a result of spekboom's presence, and its facilitation of other thicket trees and succulents, an entire ecosystem is supported, with extremely high densities of large animal species, such as kudu, black rhinoceros and African elephants. These animals rely directly on the spekboom for food, as well as on the other plants that grow alongside it due to it's soil altering growth form, and if spekboom is removed, the whole ecosystem collapses. Spekboom is by far the most important species in these environments!

This project was founded by the Subtropical Thicket Restoration Programme (STRP) which made the decision to set up a biome-wide experiment and plant plots of spekboom across the Eastern and Western Cape in  order to establish benchmarks of restoration. Roughly 300 plots, most of them 50×50 m in diameter, were planted with spekboom truncheons where thirteen different treatments were applied to assess which would yield the best survival and growth ​— and thereby guiding restoration protocols.

To learn more about this experiment, click here.

At present the Mandela University Spekboom Thicket Research group comprises three primary researchers ​— Prof. Alastair Potts, Kristen Hunt and Alec Blewett.

Right: Team photo in 2021. 

We conduct a wide range of experiments (in the field and in the laboratory) using a combination of long-standing robust ecological methods and newer state-of-the-art methods. We investigate questions ranging from how best to conduct restoration to understanding how Subtropical Thicket ecosystems operate. 

Please click here to to review our major research themes.