Improved native understorey establishment in mine waste rock in Australia's wet-dry tropics

Re-establishment of understorey in mine waste can be challenging because of its physical, chemical and microbiological characteristics. This project investigated amelioration treatments for establishing native understorey in waste rock at Ranger uranium mine, including the addition of fine sand, fertiliser, surface litter, incorporated organic matter, or a combination of sand, fertiliser and litter. Trials were established in a shade house and in situ on a waste-rock landform. Several grass and legume species had seedling emergence and growth being monitored. In situ, surface litter generally had twice as many seedlings emerge as did the other treatments and had the tallest mean height for most species, likely because it created a microclimate that retained moisture and moderated temperature. In the shade house, no treatment had significantly greater emergence than the control (except Acacia gonocarpa F.Muell. with surface litter). Fertiliser application resulted in significantly taller plants in the shade house but had no effect in situ, which suggests that under well watered conditions, plant growth in waste rock is affected by nutrient deficiency, whereas in field conditions, water supply is the main growth-limiting factor. When establishing native understorey on waste rock in hot and seasonally wet-dry climates, applying surface litter with seeds may improve initial establishment.