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In South Africa, coastal dune forests form an ecotype within the Maputaland Centre of Plant Endemism. The coastal forests in KwaZulu-Natal, South Africa, have a long history of fragmentation and destruction induced by humans. A significant portion of these forests are mined for heavy minerals such as rutile, ilmenite and zircon for some 40 years and where this mining has been followed by a continuous process of dune rehabilitation directed at restoring indigenous dune forests along part of the former mining pathways. This provides us with an outdoor laboratory for research into the ecological processes that induce forest community development.
Our research on coastal dune restoration commenced in 1991, with the support of Richards Bay Minerals, and we now maintain an extensive database on the chronosequential development of tree, understory vegetation, millipede, bird and small mammal assemblages of known ecological history. This enables us to 1) evaluate rehabilitation success and 2) develop and test hypotheses related to self-induced community development across temporal and spatial gradients.
The restoration goal along the mining path is to re-create a forest that is similar to relatively intact forests in the region. Successful dune forest rehabilitation should predictably be associated with structural and functional development of both the biotic and abiotic components of the ecosystem towards a benchmark, in this instance an area of undisturbed forest. CERU has been monitoring the ecological development in assemblages of plants and animals, as well as in soil variables (nutrient and fertility levels) that reflects on ecosystem function. The Ecological Monitoring Program evaluates the trajectory of development in ecological variables, comparing them both to trajectories obtained during previous years, and to trajectories across a chronosequence of naturally regenerating forest patches in the region. The program also evaluates the predicted endpoints of development. The program is, therefore, an important tool for mining companies (such as Richards Bay Minerals) that need to meet the objective of ecological sustainability.
Principles of succession predict that disturbances, such as those induced by mining, may bring about the development of biotic communities through primary succession. This is characterised by local colonisations and extinctions that take place in stages and result in the natural regional and local species pools being indistinguishable. The decay of differences in these species pools is expected to follow negative exponential trends. Rehabilitation does not always follow a deterministic trend. The existence of multiple stable states, chaotic or non-equilibrium dynamics, continuous disturbances and the vagaries of climate, to name a few, all prevent predictable change in groups of forest species. We are assessing the empirical evidence in support of current restoration models, using data accumulated during some 18 years of regular surveys of plant, millipede, and bird assemblages.
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