Stimulated Soil Formation in a Degraded Anthroscape: A Case Study in Southeast Spain

Extensive extractions of natural resources such as metals led to degraded landscapes oftentimes inhospitable to plants and other organisms. Conversion of such unhealthy environments to productive ecosystem requires the formation of soils. This paper reports on our efforts to accelerate the development of soils in mine wastes deposits in southeast Spain. We investigated the structural, chemical and mineralogical properties of mine tailings. These materials have low organic C (<0.5%) and N (<0.05%), high acidity (pH as low as 2.0), high electrical conductivity (up to 20 dS m⁻¹) and high levels of metals such as Zn (up to 22,000mg Zn kg⁻¹) and Pb (up to 7,000mg Pb kg⁻¹). Our results showed that organic matter (OM) from sewage sludge and pig manure when added together with calcite from marble cuttings resulted to accumulations of OM as cappings on calcite particles. These OM caps hold enough water and nutrients to support the establishment of seedling in amended tailing materials. It is clear from micromorphological examinations that granular structure starts to form in the interface of OM caps and root zone of seedlings. Our results suggest that OM can be effectively enriched in mine wastes deposits through simultaneous additions of OM and calcite. Our findings might be useful to accelerate the establishment of functional ecosystem characterized by healthy soils with granular structure in degraded anthroscapes.