Effects of understory cover on tree recruitment in gold mining rehabilitation in monsoonal woodlands in Northern Territory Australia

Gold mining is one of the principal industries in the Northern Territory of Australia. Most of the mining occurs in monsoonal savanna woodland dominated by Eucalyptus and Acacia species with a grass understory. After mining, rehabilitation includes broadcasting a seed mix of Eucalyptus, Acacia and other tree species. Subsequent to initial establishment, continuing recruitment is important to ensure the rehabilitated vegetation community is sustainable. This study assessed relationships between tree recruitment and environmental parameters in gold mine rehabilitation areas. Tree density, sapling density, tree seedling density, grass biomass and soil cover were measured across 14 rehabilitation sites and 7 analogue sites. In natural woodland average sapling and seedling densities were two times greater than in mine rehabilitation areas. In general ground cover, tree density and the presence of cattle grazing are weakly correlated to tree recruitment. It suggested that after more than 10 years of rehabilitation, tree recruitment in mine rehabilitation is common but is yet to develop to recruitment levels observed in mature woodland. Tree recruitment monitoring is important to ensure vegetation sustainability in mine rehabilitation and is a useful tool to guide land management.