The effect of burning, soil scarification and seeding on the understorey composition of 12 year-old rehabilitated bauxite mines in Western Australia

Summary

The effect of burning, soil scarification and seeding on 11 to 13-year-old rehabilitated bauxite mines was examined to assist the development of a prescription for increasing establishment of native tree and understorey species. Scarified and non-scarified treatments were investigated following burning in autumn and spring, and in no burn areas. All treatments were seeded with a mix containing jarrah (Eucalyptus marginata), the native overstorey dominant, and 37 understorey species. Plant response was measured as the density of all plants, weeds, eastern Australian eucalypts, acacias and jarrah as well as native species numbers and the Shannon-Weiner diversity index. Nearly all of these measures were significantly higher in the burnt compared to the unburnt treatments. Species numbers, total plant density. Acacia density and jarrah density were higher following autumn burning than spring burning. However, the density of eastern Australian eucalypt seedlings was also significantly increased by autumn burning which has undesirable implications if the native overstorey dominant, jarrah, is to be established in these areas. Seeding an understorey species mix significantly increased species richness, particularly in burnt areas. Soil scarification significantly increased diversity in the autumn treatments. Burning rehabilitated sites in spring with no soil scarification appears to be the best prescription to minimise the abundance of eastern Australian eucalypts observed following autumn burning, while seeding an understorey seed mix on these areas will increase species richness.