Interactions between soil covers and rainfall affect post-mining plant restoration in a semi-arid Banded Iron Formation

Soil moisture and physical characteristics strongly influence plant-available water and surface crust strength, which affect seedling emergence. We test interactions between rainfall amount and topsoil and waste rock blends and their impact on restoration outcomes in a semi-arid environment. Seedling emergence was evaluated in eight species across three winter rainfall treatments (low (ambient) 68 mm, equivalent to 1st decile; median 144 mm; and high 182 mm, 8th decile) and three soil cover treatments (topsoil, waste rock and topsoil+waste rock blend (3:1)) to assess the effect of rainfall amounts, soil cover blend, and their interactions on plant recruitment in restoration. Seedling emergence for all species was <1% under the low winter rainfall (i.e. deficit) and significantly higher (1–5%) for median and high rainfall scenarios. Soil covers that included topsoil had nearly 3-times more seedling emergence than waste rock cover. Thus, restoration success can be significantly hampered in years with below median rainfall. When rainfall conditions were favourable, however, blended soil covers performed similarly to topsoil covers, and may be a useful approach for restoration when topsoil is a limited resource.