Assessment of topsoil handling techniques for rehabilitation of sites mined for bauxite within the jarrah forest of Western Australia.
Abstract
Topsoil handling strategies used in bauxite mine rehabilitation were evaluated for their effects on seedling numbers, diversity and cover. These were compared with a native jarrah forest site. Double-stripping involved the separate removal and direct return of the top 5 cm of topsoil over a lower stockpiled layer. This led to increased groundcover compared with direct return of the whole mixed profile or return of stockpiled topsoil. Germinable seed load decreased with depth in forest topsoil. Forested sites had greater cover and more species present than rehabilitated minesites up to 5 yr old. Double-stripping resulted in diversity values most nearly approaching those of the forest. Dominance-diversity plots for double-stripped sites tended to lognormality after 4 years. Possible improvements in handling and timing of the double-stripping technique are discussed.<new para>ADDITIONAL ABSTRACT:<new para>Soil stripped from the top 40 cm was: (1) stockpiled for 2 yr and respread; (2) immediately respread; (3) stockpiled for 2 yr, respread, and covered with soil freshly removed from the top 5 cm of another mined site. Method (3) gave significantly higher seedling densities and the highest species diversity, close to that of natural forest. Laboratory tests showed that 93% of germinable seeds were in the top 2 cm of topsoil. Dominance-diversity curves for (3) tended towards lognormality after 4 yr, but (3) still had only half the cover of mature forest.