Sand Mining Restoration on the Swan Coastal Plain using Topsoil – Learning from Monitoring of Previous Rehabilitation Attempts

摘要

This paper reports on the results of several years of monitoring rehabilitation at a silica sand minernon the Swan Coastal Plain, south of Perth. Mining here occurs below the regional watertable andrnleaves a post-mine landscape of dredge pond voids (pit lakes) with surrounding battered slopes.rnThe restoration we recommended was to develop the pit lakes as wetlands of regional analogue andrnvalue. Several different restoration techniques have been applied to re-vegetate pit lake slopes overrnmany years which have enabled an evaluation of reasons for success/failure of different restorationrnapproaches. Learning acquired clearly showed the benefi ts of using fresh topsoil for restoration overrntopsoil that has been stockpiled for several years. Most topsoil used in restoration was from seasonalrnwetlands and consequently restoration was most successful in the riparian zone from the edge of pitrnlakes to about 2 m vertically above the water table. Topsoil restored areas above this level remainedrnpoor in plant species and cover. Conversely, remedial seeding/planting proved largely unsuccessful.rnPermanently and seasonally flooded pit lake margins recolonised relatively quickly and successfullyrnwith native sedges and rushes. Development of rehabilitated upper slope plant communities overrntime was evident with loss of typical wetland species and greater growth and survivorship of uplandrnand dampland plant species on mid to upper rehabilitated slopes. Plant communities of lower slopesrnshowed a converse pattern of development, with a shift towards a more typical wetland composition.rnWe believe matching topsoil to site and development of topographic profi les similar to naturalrnwetlands of the region are the keys to optimising restoration success of sand mines with shallowrnwater tables.