It is of advantage to the reclamationist to have some conceptual understanding of natural succession, and even more important to have a practical knowledge of the climax vegetation and natural successional processes in the region where he or she works. Factors that can limit succession on reclaimed land include lack of appro!)riate seed source unsuitable soil conditions, and climatic or microclimatic factors. The use of natural success10nal processes is' not incompatible with a certain amount of management, and measures that can be. used to initiate or enhance succession include the use of physical site stabilization or a nurse crop, an enhanC<:d nanve seed source, ".r the use of minimal soil amelioration. An understanding of seed ecology, patch dynamics and the role of s01l microoorganisms are also invaluable to the reclamationist The extensive literarure on colonization and succession, both on untreated and treated wastes of various types and in various climates, is reviewed.
The concept of successionThe concept of ecological succession has been at the heart of ecological thinking since the time of Clements (1916Clements ( , 1936. According to Clementsian thinking, succession is an autogenic process, in which vegetation develops on a formerly bare substrate as a sequence of plant communities, each one altering the environment such that it favours the one that follows, culminating in a relatively steady-state -the climax. This concept of succession came to be known as "Relay Floristics" (RF). Egler (1954) introduced another concept of succession, which suggested that the species composition early in the successional process can have a great influence on the final composition. This concept, which would be especially applicable to secondary successions such as those following industrial disrurbance, was known as Initial Floristic Composition (IFC). A lesson on the importance of "initial composition" can be learned from the Mount St. Helen's eruption, where "late successional" species such as hemlock and true fir became established on the debris slide within a year (Dale, 1992). Similarly, Bellairs and Bell (1992) found that initial species composition largely determined vegetation development on sand-mined soils in Western Australia. (1977) presented two further models of succession, the "tolerance" model and the "inhibition" model. The tolerance model incorporates both the RF and the IFC approaches, since it proposes that vegetational change is the result of the superior success of the species best able to make use of the available resources. These species will normally include both "pioneers" and species already established.In the context of revegetation, the tolerance model is likely to include a third component -the species sown or planted by the rec.lamationist. The model is particularly relevant m the case of revegetated land, in view of the use of fertilizers as a tool in implementing revegetation and in managing revegetated land. A plant community is the result of the interaction between the ec...