Restoration of soils post-mining requires key solutions to complex issues through which the disturbance of topsoil incorporating soil microbial communities can result in a modification to ecosystem function. This research was in collaboration with Iluka Resources at the Jacinth-Ambrosia (J-A) mineral sand mine located in a semi-arid chenopod shrubland in southern Australia. At J-A, assemblages of microorganisms and microflora inhabit at least half of the soil surfaces and are collectively known as biocrusts. This research encompassed a polyphasic approach to soil microbial community profiling focused on "biobanking" viable cyanobacteria in topsoil stockpiles to facilitate rehabilitation. We found that cyanobacterial communities were compositionally diverse topsoil microbiomes. There was no significant difference in cyanobacterial community structure across soil types. As hypothesised, cyanobacteria were central to soil microprocesses, strongly supported by species richness and diversity. Cyanobacteria were a significant component of all three successional stages with 21 species identified from 10 sites. Known nitrogen-fixing cyanobacteria Symploca, Scytonema, Porphyrosiphon, Brasilonema, Nostoc, and Gloeocapsa comprised more than 50 % of the species richness at each site and 61 % of the total community richness. In the first study of its kind, we have described the response of cyanobacteria to topsoil stockpiling at various depths and ages. Cyanobacteria are moderately resilient to stockpiling at depth and over time, with average species richness greatest in the top 10 cm of the stockpiles of all ages and more viable within the first 6 weeks, indicating poten-tial for biocrust re-establishment. In general, the resilience of cyanobacteria to burial in topsoil stockpiles in both the short and long term was significant; however, in an arid environment recolonisation and community diversity could be impeded by drought. Biocrust re-establishment during mine rehabilitation relies on the role of cyanobacteria as a means of early soil stabilisation. At J-A mine operations do not threaten the survival of any of the organisms we studied. Increased cyanobacterial biomass is likely to be a good indicator and reliable metric for the re-establishment of soil microprocesses.
10Mining rehabilitation requires key solutions to complex issues relating to ecosystem function. In arid landscapes, the removal or disturbance of topsoil incorporating soil microbial communities can result in a shift in ecosystem function. Soil surfaces in arid regions are protected by biocrusts that regulate soil moisture, sequester carbon and fix significant quantities of atmospheric nitrogen. Cyanobacteria often dominate these bioactive surfaces and work as ecosystem engineers in that they are in sufficiently large quantities they initiate biocrust establishment and facilitate soil surface stabilisation. Cyanobacterial 15 exopolymeric secretions form cohesive and protective layers at the soil surface that minimise wind erosion. This research encompassed soil microbial community profiling (using a polyphasic approach) with a focus on 'biobanking' topsoil for rehabilitation purposes. The research was in collaboration with Iluka Resources at Jacinth-Ambrosia (J-A) mineral sand mine located in a semi-arid chenopod shrubland in southern Australia. At J-A diverse biocrusts included a significant representation of cyanobacteria, lichens and mosses that inhabited nearly half of all soil surfaces. Cyanobacterial community structure at J-A 20 was comprised of a variety of species having a range of attributes that contributed to their resilience and survival in an arid environment. Stockpiling from shallow scrapings and storage at low profiles appeared beneficial in microbial biobanking cyanobacterial inoculum that would facilitate recovery over time. These studies have provided information for the establishment of a monitoring program that assesses the re-establishment of biocrusts following mining. Following soil stockpiling that occurred during the mining process, cyanobacterial taxa recovered at different rates. Cyanobacterial strategies 25 central to survival include exopolymeric production, spectral adaptation, nitrogen fixation and motility. Biocrust reestablishment during mining rehabilitation relies on the role of cyanobacteria as a means of early soil stabilisation. Provided there is adequate cyanobacterial inoculum in the topsoil stockpiles their growth and the subsequent crust formation should take place largely unassisted. Ongoing monitoring of biocrust recovery is important as it provides an effective means of measuring important soil restoration processes. 30Biogeosciences Discuss., https://doi
Supplementary Tables Table S1: Descriptions of sources for intact biocrusts used to characterise the cyanobacterial communities: Site vegetation associations: SMU 1 -Red Mallee: Eucalyptus oleosa ssp. oleosa = open Mallee/Myall woodland; SMU 2 -Chenopod Shrubland: Maireana sedifolia and Atriplex vesicaria; SMU 3 -Western Myall: Acacia papyrocarpa Maireana sedifolia = open Myall woodland Site 1 occurs in a transition between SMU 2 and SMU 3 but was treated as most like SMU 2; Site 6 originated from SMU 3 -*2YO stockpile crust type determined in situ also with mosses present; TSF = Tailings storage facility. Site no. Primary Vegetation SMU Biocrust types Site identifier and description
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