Early seedling establishment on aged Tasmanian tin mine tailings constrained by nutrient deficiency and soil structure, not toxicity

Abstract

Revegetation of exposed wastes at historically abandoned mines is frequently constrained by inherent characteristics of poorly developed and contaminated soils. We tested whether the establishment of seedlings on 85-year-old arsenic rich tailings deposits at an abandoned tin mine in north-east Tasmania was limited by toxicity, nutrient limitation or structural factors. We conducted soil analyses, and tested growth of six native species in pot studies utilising both fertiliser treatments and a replacement series involving tailings and potting medium. An in situ three-year field trial was also conducted to assess the effects of adding sand, compost and biochar on plant growth and water infiltration. Analyses of the tailings identified a finely laminated structure and potential manganese, magnesium and potassium deficiencies. There was no evidence of microbial inhibition or adverse metals toxicity, pH or salinity effects. The pot trial indicated nutrient limitation acting on each of the species tested. Physical amendment within the field trial resulted in a highly significant and sustained improvement in infiltration rate, as well as improved growth in three of the six species tested. We conclude that the correction of nutritional and physical deficiencies in surface soils should overcome limitations to the early establishment of native seedlings at this site. This study shows that systematic site assessment and targeted trials is a valuable first step in the revegetation of previously recalcitrant sites.