The Evaluation of the Effectiveness of Revegetation Methods Currently Used By Abosso Goldfields for Reclamation of Degraded Lands

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The effectiveness of re-vegetation methods for lands disturbed by mining operations was investigated at Abosso Goldfield Ltd mine concession between July and August 2010. Three categories of re-vegetated sites namely (1) decommissioned tailings storage facility (South Tailings Storage facility: STSF-L), (2) borrow area (South Tailings Storage facility Borrow Pit; STSF-Bp) and (3) waste rock dump (Tomento South Waste Rock Dump: TMS) and a secondary forest (Rex Haul road forest: RHR-F) as control site were used for the study. For each site, reconnaissance survey was conducted to select appropriate sites for the study. Sampling was conducted in 25m X 25m main plot representative of the selected sites. The main plot was sub-divided into twenty-five 5m X 5m sub-plots and 10 sub-plots were randomly selected for the study. Flora survey for composition and abundance were conducted in the 10 selected sub-plots. Composite soil samples for depth of 0-20cm and 20-40cm were obtained, using a screw auger, for soil analysis. Earthworm extraction using the 2% formalin was done in three 30cm X 30cm quadrats laid in the 10 selected sub-plots. The findings of the study showed that topsoil management and replacement is very vital in the recovery of disturbed lands. Of the three revegetation methods studied, the method at TMS was the most effective followed by the method at STSF-L and the least effective was the method at STSF-Bp. It was also found that the use of Pueraria sp, Acacia mangium and Leucaena leucocephala were beginning to pose invasion problems. Based on these findings, it was recommended that: One, subsoil pulverization followed by sufficient topsoil replacement should be ensured in the revegetation of Borrow pits. Two, revegetation at STSF-Bp be reinitiated in order to meet mine closure reclamation objectives. Three, thickness of replaced topsoil should be increased to better facilitate the integrated revegetation approach and reduce maintenance cost. Four, to arrest species invasion problems, locally available species such as Centrosema pubescens should be used in place of Pueraria sp for cover material whereas for tree species, Anacardium occidentale, Casuarina equisetifolia, Gliricidia sepium and Musanga cecropioides be used in place of Acacia mangium and Leucaena leucocephala.
A thesis submitted to the School of Graduate Studies, Kwame Nkrumah University of Science and Technology in partial fulfilment of the requirement for the award of Master of Science degree in Environmental Science, August-2011