Comparison of Post-Mine Rehabilitated and Natural Shrubland Communities in Southwestern Australia

Following mineral sand mining near Eneabba, southwestern Australia, rehabilitation managers have the difficult task of restoring shrubland communities of exceptional plant species richness. Species diversity, composition, structure, and key functional attributes in four mined sites rehabilitated 8 (R8) to 24 (R24) years ago were compared with those of typical nearby natural areas classified on the basis of substrate type (Low and High sand Dunes, shallow sand Swales, sand over Laterite, and sand over Limestone). The rehabilitated sites (except R8) had more species (about 140) than natural sites (about 100) in 40 x 40-m plots, with 12-37% species in common with natural sites. Rehabilitated sites were more similar in composition to each other than they were to the natural sites, with two strong colonizers, the fire-killed Acacia blakelyi and the fire-tolerant Melaleuca leuropoma, universally present. Dendrograms and ordinations based on composition and cover showed that rehabilitated sites grouped with each other before they did with the Dune and Swale sites (physically closest), and last with the Laterite and Limestone sites. Plant densities for R16 and R24 were about half those of the High Dune and Limestone, and about a quarter those of the Swale and Laterite. Fire resprouters were under-represented in the rehabilitated sites. Growth form distribution in rehabilitated sites was most similar to those of the dunes, with some woody shrubs up to 2.5 m tall present. Total iron and soil hardness (penetrability) were the only soil factors consistently different (higher) in the rehabilitated sites.