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Abstract The present study aimed to characterize key physico-chemical and mineralogical attributes of magnetite iron (Fe) ore tailings to identify potential constraints limiting in situ soil formation and direct phytostabilization. Tailings of different age, together with undisturbed local native soils, were sampled from a magnetite mine in Western Australia. Tailings were extremely alkaline (pH > 9.0), with a lack of water stable aggregate and organic matter, and contained abundant primary minerals including mica (e.g., biotite), with low specific surface area (N 2 -BET around 1.2 m2 g−1). These conditions remained relatively unchanged after four years' aging under field conditions. Chemical extraction and spectroscopic analysis [e.g., X-ray diffraction (XRD) and synchrotron-based Fe K edge X-ray absorption fine structure spectroscopy (XAFS) analysis] revealed that the aging process decreased biotite-like minerals, but increased hematite and magnetite in the tailings. However, the aged tailings lacked goethite, a compound abundant in natural soils. Examination using backscattered-scanning electron microscope - energy dispersive X-ray spectrometry (BSE-SEM-EDS) revealed that aged tailings contained discrete sharp edged Fe-bearing minerals that did not physically integrate with other minerals (e.g., Si/Al bearing minerals). In contrast, Fe minerals in native soils appeared randomly distributed and closely amassed with Si/Al rich phyllosilicates, with highly eroded edges. The lack of labile organic matter and the persistence of alkaline-saline conditions may have significantly hindered the bioweathering of Fe-minerals and the biogenic formation of secondary Fe-minerals in tailings. However, there is signature that a native pioneer plant, Maireana brevifolia can facilitate the bioweathering of Fe-bearing minerals in tailings. We propose that eco-engineering inputs like organic carbon accumulation, together with the introduction of functional microbes and pioneer plants, should be adopted to accelerate bioweathering of Fe-bearing minerals as a priority for initiating in situ soil formation in the Fe ore tailings. Graphical abstract Unlabelled Image Highlights • Magnetite Fe ore tailings were strongly alkaline and lack of organic carbon. • Biotite weathering in the tailings without amendments were very slow. • Fe oxides in the tailings lacked association with Al-/Si- minerals for aggregation. • Natural weathering of the tailings resulted in little physicochemical improvements. • Pioneer plants and microbes would be required to accelerate tailings weathering. [ABSTRACT FROM AUTHOR]

Topsoil replacement is a standard procedure in restoration of mined landscapes as it provides a source of propagules via the soil seed bank, as well as provides favourable physical, chemical and microbiological properties for plant establishment. With the availability of topsoil frequently limited in mining, soil cover designs that maximise the use of this resource across the newly-created surfaces after mining should be considered. In this paper, we examine the use of different soil covers and their influence on seedling recruitment for restoration of a Threatened Ecological Community (TEC) with limited topsoil. The properties of a standard topsoil and topsoil diluted with waste-rock to optimise spread were compared between two topsoil sources with different textures and a fine-textured waste material that is a mining by-product. We studied the physicochemical and hydrological traits of five soil covers (unblended TEC topsoil; TEC topsoil mixed with waste rock; fines; fines mixed with waste rock, and waste rock) with two TEC topsoil sources (plateau and hillslope). Soil characterisation included texture, gravel content, soil surface crust strength, soil moisture and temperature, and surface infiltration. Finally, we quantified seedling emergence for four key taxa sown ( Acacia acuminata, Allocasuarina acutivalvis , Melaleuca nematophylla, Waitzia nitida ) and the seedling community arising from the topsoil seedbank and naturally dispersed seeds, and related this emergence with the soil properties. The standard topsoil cover promoted the greatest seedling emergence showing marked differences between the two topsoil provenances. Importantly, the addition of waste rock to topsoil did not compromise the ability of topsoil to support seedling emergence and is therefore a useful strategy to maximise this resource. Overall, our results show the importance of hydrological properties of soil covers for seedling recruitment and highlight the importance of topsoil selection in restoration success. [ABSTRACT FROM AUTHOR]

Abstract: Karrikins are a chemically defined family of plant growth regulators discovered in smoke from burning plant material. Karrikins are potent in breaking dormancy of seeds of many species adapted to environments that regularly experience fire and smoke. The recent discovery that karrikins trigger seed germination and control seedling growth in taxa that would rarely experience fire indicates that their significance could extend far beyond fire ecology. This is exemplified by new studies showing that seeds of Arabidopsis thaliana respond sensitively and specifically to karrikins in smoke. These exciting discoveries might be explained if karrikins are produced in the environment by processes other than fire, such as by chemical or microbial degradation of vegetation in response to disturbance of the soil or removal of the plant canopy. Another hypothesis is that plants contain endogenous karrikins that function naturally in the control of seed germination and that species from fire-prone habitats have evolved to respond also to exogenous karrikins. A variant on this hypothesis is that karrikins mimic endogenous plant hormones such as terpenoids that control seed germination. The evidence for these hypotheses is discussed, but whatever the explanation karrikins are now firmly established as an important family of naturally occurring plant growth regulators. [Copyright &y& Elsevier]