Mine Closure - Mining and the Environment: From Ore to Metal - page 821

FIGURE 21.4
Vetiver Grass Hedges Established on
Slope of Waste Rock Storage

advantage is the much lower requirement for surface drains where Vetiver Grass is used.
Further, while surface banks i ll over time, the hedges are self-maintaining.

Plant Succession

Plant succession is the natural progression in which different plant communities appear
over time on the same area. Each time that the vegetation is removed, for example by i re,
logging or landslip, the succession process commences with the appearance of the pioneer
community. Subsequently, several different communities may come and go before the cli-
max community becomes established.
Attempts are often made to 'short circuit' the succession process by transplanting seed-
lings of climax tree species early in the rehabilitation process. These attempts are usually
unsuccessful as the climax species have particular requirements that preclude their estab-
lishment until the i nal stage of succession. In particular, many climax canopy species in
the humid tropics require dense shade for the i rst few years of their lives. Succession is a
long, slow process requiring decades, even centuries to complete each cycle. Accordingly,
it is not possible for natural vegetation to approach climax conditions within a few years
of rehabilitation. It is important that this is recognized in the ongoing management proce-
dures, in interpretation of monitoring data and in the selection of acceptance criteria.

Succession is a long, slow process
requiring decades, even centuries
to complete each cycle.

Biodiversity of Rehabilitated Areas

A common goal of rehabilitation is to produce biodiversity comparable to that which
occurred prior to mining. However, for some of the reasons already discussed this can only
be a long-term goal. In a tropical forest situation, primary forest communities at or close
to climax condition, have a relatively low diversity of plants. Secondary forests undergo-
ing succession following logging, commonly have much higher diversity. The maximum
diversity results from a mixture of forest communities, with different aspects and soil
types, and with areas at different stages of succession.