Plant recruitment from the soil seed bank depends on topsoil stockpile age, height, and storage history in an arid environment

The topsoil native seed bank is a valuable resource in post-mining rehabilitation capable of providing a cost-effective means for restoring plant diversity. However, the value of the native soil seed bank is affected by topsoil management practices especially long-term stockpiling. Salvaged topsoil is usually stockpiled until mining operations are completed and landforming has been performed. This study compared the germinable soil seed bank of freshly harvested topsoil against the effects of stockpile age (stored for 1 and 3 years) and depth (top and bottom 50 cm of 2-m-high stockpiles). Total native seedling emergence was greater from the 1-year-old stockpile but was dominated by annuals including species commonly found on disturbed sites. Seedling emergence of perennial species was more than 4-fold greater in fresh topsoil than in the 1-year-old stockpiles, and 2-fold greater than the bottom 50 cm of 3-year-old stockpiles, with no difference in the top 50 cm of the 3-year-old stockpiles. Although there was no difference in total emergence between the top and bottom of stockpiled topsoil, there was greater emergence of the ecologically important Triodia grass genus from the top than bottom of 3-year-old stockpiles. Species composition of the seed bank in the 1-year-old stockpile was different to fresh topsoil and the 3-year-old stockpile possibly reflecting differences in species composition of vegetation present when topsoil was initially salvaged for stockpiling, confounding comparisons between years. This study demonstrates the importance of conducting soil seed bank analysis of stockpiled topsoil to be used in restoration programs.