The effect of rehabilitation treatment following high dune mining on North Stradbroke Island was examined with special reference to the effect of fertilizer and exotic grass cover on successional development. Native regrowth on areas mined three years previously was also monitored.
The successional trends over the first two years were:
1. unfertilized treatment: negligible regrowth.
2. complete fertilizer treatment: short lived/pioneer legumes à long lived species (tree/shrub/herb strata) .
3. fertilizer and exotic grass cover (full rehabilitation) treatment: short lived/pioneer legumes à short lived/ non-legumes (shrub stratum).
Comparison with the historically normal form of disturbance, fire, suggests that the initial application of fertilizer artificially simulates the characteristic post-disturbance mobilization of nutrient. In the absence of regrowth from vegetative reproduction promotion of rapid recovery is particularly important.
Whether the application of fertilizer will alter long term successional development can only be a matter of speculation. The potential for toxic effects of P:N imbalance on regenerating heath species is discussed. The exotic grass cover favoured the growth of the short lived leguminous species both increasing the sensitivity and susceptibility to fire of the developing vegetation.
Observation of the older rehabilitated areas indicates that short lived leguminous species on the full rehabilitation treatment will be gradually replaced by long lived species. It is also demonstrated that close proximity to a natural seed source accelerates successional development. Exotic grass cover retards the development of a native herb stratum. The space and favourable microclimatic conditions provided within a herb stratum appear to be important for the successful establishment of tree species. Initially, at least, the dense exotic grass cover may cause a truncated successional development.
Recommendations for changes are suggested, for the mining operation and the subsequent rehabilitation treatment, The environmental impact of sand mining as a land use is discussed.