Challenges in Natural Forest Regeneration in Mine Rehabilitation

Natural regeneration of secondary forests on degraded lands is uncertain process impeded by combination of factors including human pressure, recurrent of fires persistence of dominant grasses and other non-woody species, unfavorable non-woody species, unfavourable microclimate conditions, soil infertility exhaustion of soil seed banks and root stock and low rate of seed input from surrounding forest. Several hundreds years are required for the plant community to reach stage of successional stability. Mixed native species has improved the fertility status and productive capacity of phosphate mine spoil and favored biological invasion of various natural invader. Natural invasion of trees into revegetated sites can be affected by the types of plant species already growing at the site as well as by resources availability. Ecologists have shown that resource competition alleopathy and facilitation have important effect on plant community organization. The natural revegetation by trees was a complex process controlled primarily by dispersal mechanism of tree species. The mined sites pre-vegetated produced by various types of mining may have intrinsic value because they represent perturbation dependent plant communities of early successional status. Plots planted with early sucessional species characteristic of particular region are more conducive to the entry of other species. Sometimes eucalyptus tree contribute higher input on different mine spoils, the large areas of ground surface beneath eucalyptus remains completely bore ground or limited extent vegetation. The use of legumes in seed mixtures for long-term supply of nitrogen is necessary for the colonization and development of low maintenance vegetation cover on mine disturbed sites. The vegetation of limestone dolomite quarries appears to have features of both primary and secondary succession, which was relatively rapid in limestone mines. Natural invasion by various plant species takes place with the age of spoil. The predominance of legumes on revegetated mine sites suggested that there is an advantage in colonizing legumes on spoils especially low in available nitrogen. The older mined sites are considerably less sucessionally advanced that those sites having spoiled with relatively more silt and clay. During restoration of surface of mines globally ultimate objective of reclamation is to create diverse and stable ecosystem so initial reclamation should be designed to stabiles habitat for natural succession.