Abstract

Introduction: Destruction of vegetation resources emanating from deposition of mine wastes is a serious environmental problem. Conventional plant species restoration methodologies are costly and feasible only on a small scale. The current study was focussed on developing phytostabilisation protocols involving the application of limestone, compost, selected tree species and assessing the re-establishment of plants in polluted soils.

Methods: Early establishment of plant species under Eucalyptus grandis, Senna siamea and Leucaena leucocephala planted on mine tailings and pyrite soils amended with compost, limestone and limestone+compost was studied. Four plant inventories were conducted on the study plots and surrounding plant communities, involving enumeration of the plant species and estimation of their ground covers. Physico-chemical characteristics of the soils of the study plots were determined each time an inventory was conducted. Data were analysed using R statistical packages vegan and lme4.

Results: Mine tailings and pyrite soils had extremely low pH, poor nutritional status, low organic matter content and elevated concentrations of heavy metals as compared to the unpolluted soils. Before treatment, species richness, diversity and plant cover were extremely low with most of the ground being completely bare. Treatment of the soils significantly improved the physico-chemical characteristics starting a plant succession that increased the number of species from 18 to 215 different species, belonging to 131 genera and 34 families. Plots of the leguminous tree species Senna siamea and Leucaena leucocephala had significantly more species than the non-leguminous Eucalyptus grandis. Early changes in species composition of the restoration plots were minimal. Correspondence analysis (CA) revealed significant differences in species composition between the experimental plots and the plots at the unpolluted site.

Conclusion: Application of amendment material that significantly alters the physico-chemical characteristics of mine wastes is pre-requisite for their phytostabilisation. Leguminous tree species Senna siamea and Leucaena leucocephala have a higher potential for phytostabilisation of pyrite and copper tailings as their growth led to the establishment of understory plant communities with higher species diversity and cover.

Keywords: Compost, correspondence analysis, dynamics, limestone, phytostabilisation, pyrite, restoration, tailings