Are current seed storage approaches suitable for Macrozamia fraseri (Cycadales), a temperate species used in restoration?

In this study, we focused on understanding key storage traits of seeds from Macrozamia fraseri, an unusual though important species that is impacted by mining. To support current restoration activities, large amounts of seed from M. fraseri have been regularly collected and stored for up to 8 years under standard seed banking conditions (5°C and 20% relative humidity), though in situ recruitment from directly sown seed is poor. To investigate the underlying constraints to germination on demand, we set out to assess the viability of M. fraseri seeds that had been stored in a restoration seed bank from 6 to 66 months. Seed moisture content (MC) (fresh weight basis) was also determined for seeds with different storage histories to ascertain whether M. fraseri seeds display traits (i.e. high MC) that might suggest non-orthodox seed storage behaviour. The youngest seed accession (6 months old) was found to have a high MC (45.8 ± 5.4%-fresh weight basis), and >50% viability. In comparison, older (>30 months old) accessions were observed to have a marked reduction in both seed MC (10-35% MC) and viability (0-29.4%). While preliminary, we conclude that M. fraseri seeds appear to lose viability during conventional storage with younger accessions displaying both a higher seed MC and viability, compared to accessions stored for longer. Given the significance of these results, future research activities are recommended to better understand the interplay between seed MC and storage environment and how this relates to the seasonally dry Mediterranean climate where this species naturally occurs. As well, storage and propagation approaches are proposed to increase success when using M. fraseri for conservation and restorative activities.

Germination physiology of Cochlospermum fraseri (Bixaceae), a deciduous tree from Northern Australia with physical seed dormancy.

Cochlospermum fraseri ('Kapok', Bixaceae) is a deciduous tree widely distributed throughout semi-arid and monsoon tropical northern Australia, and an important species for ecological restoration in the region. We aimed to better understand the seed biology and ecology of C. fraseri to determine the mechanisms by which seed dormancy might be alleviated, and the conditions that support germination to inform the use of this species in restoration. Dormancy breaking treatments (wet heat, dry heat, scarification) commonly applied to species with physical seed dormancy (PY) were tested along with stratification at 5-35°C (nine treatments). Following dormancy alleviation, seeds were germinated at nine temperatures (5 to 40°C) and five water potentials (0 to -0.8 MPa) to understand environmental thresholds that regulate germination physiology in non-dormant seeds. A proportion of seeds (<0.3) lose dormancy naturally in response to warm (25 to 35°C) moist conditions, which dislodges the hypostase plug that prevents water uptake, whilst neither dry (≥100°C) nor wet (~100°C) heat were effective. Dormancy loss was also achieved by exposing seeds to concentrated (95-98% v/v) sulphuric acid for 3-7 hours, after which high proportions (>0.75) of germination were observed. Cochlospermum fraseri seeds possess PY, which is alleviated by seasonal temperatures that occur when soil moisture is high, allowing seeds to employ a risk-adverse strategy and maximize establishment success in episodic environments with stochastic rainfall events. The understanding of dormancy alleviation requirements gained here adds to our knowledge of PY worldwide and recruitment dynamics in the Australian monsoonal tropics and will aid land managers and restoration practitioners by informing both seeding sites and optimal time for in situ sowing as well as the potential capacity of this species to form a persistent soil seed bank.

Inorganic phosphorus nutrition in green-leaved terrestrial orchid seedlings.

BACKGROUND AND AIMS: Many terrestrial orchids have an obligate dependence on their mycorrhizal associations for nutrient acquisition, particularly during germination and early seedling growth. Though important in plant growth and development, phosphorus (P) nutrition studies in mixotrophic orchids have been limited to only a few orchid species and their fungal symbionts. For the first time, we demonstrate the role of a range of fungi in the acquisition and transport of inorganic P to four phylogenetically distinct green-leaved terrestrial orchid species (Diuris magnifica, Disa bracteata, Pterostylis sanguinea and Microtis media subsp. media) that naturally grow in P-impoverished soils. METHODS: Mycorrhizal P uptake and transfer to orchids was determined and visualized using agar microcosms with a diffusion barrier between P source (33P orthophosphate) and orchid seedlings, allowing extramatrical hyphae to reach the source. KEY RESULTS: Extramatrical hyphae of the studied orchid species were effective in capturing and transporting inorganic P into the plant. Following 7 d of exposure, between 0.5 % (D. bracteata) and 47 % (D. magnifica) of the P supplied was transported to the plants (at rates between 0.001 and 0.097 fmol h-1). This experimental approach was capable of distinguishing species based on their P-foraging efficiency, and highlighted the role that fungi play in P nutrition during early seedling development. CONCLUSIONS: Our study shows that orchids occurring naturally on P-impoverished soils can obtain significant amounts of inorganic P from their mycorrhizal partners, and significantly more uptake of P supplied than previously shown in other green-leaved orchids. These results provide support for differences in mycorrhiza-mediated P acquisition between orchid species and fungal symbionts in green-leaved orchids at the seedling stage. The plant-fungus combinations of this study also provide evidence for plant-mediated niche differentiation occurring, with ecological implications in P-limited systems.

Evaluating restoration trajectories using DNA metabarcoding of ground-dwelling and airborne invertebrates and associated plant communities.

Invertebrates are important for restoration processes as they are key drivers of many landscape-scale ecosystem functions; including pollination, nutrient cycling and soil formation. However, invertebrates are often overlooked in restoration monitoring because they are highly diverse, poorly described, and time-consuming to survey, and require increasingly scarce taxonomic expertise to enable identification. DNA metabarcoding is a relatively new tool for rapid survey that is able to address some of these concerns, and provide information about the taxa with which invertebrates are interacting via food webs and habitat. Here, we evaluate how invertebrate communities may be used to determine ecosystem trajectories during restoration. We collected ground-dwelling and airborne invertebrates across chronosequences of mine-site restoration in three ecologically disparate locations in Western Australia and identified invertebrate and plant communities using DNA metabarcoding. Ground-dwelling invertebrates showed the clearest restoration signals, with communities becoming more similar to reference communities over time. These patterns were weaker in airborne invertebrates, which have higher dispersal abilities and therefore less local fidelity to environmental conditions. Although we detected directional changes in community composition indicative of invertebrate recovery, patterns observed were inconsistent between study locations. The inclusion of plant assays allowed identification of plant species, as well as potential food sources and habitat. We demonstrate that DNA metabarcoding of invertebrate communities can be used to evaluate restoration trajectories. Testing and incorporating new monitoring techniques such as DNA metabarcoding is critical to improving restoration outcomes.

Indigenous and local communities can boost seed supply in the UN decade on ecosystem restoration.

The UN Decade of Ecosystem Restoration is poised to trigger the recovery of ecosystem services and transform structural injustices across the world in a way unparalleled in human history. The inclusion of diverse Indigenous and local communities to co-create robust native seed supply systems is the backbone to achieve the goals for the Decade. Here we show how community-based organizations have co-developed native seed supply strategies for landscape restoration from the bottom-up. We draw on the interconnections over two decades of seed networks in Brazil and the emerging Indigenous participation in native seed production in Australia. From an environmental justice perspective, we provide a participatory seed supply approach for local engagement, noting local geographical, social and cultural contexts. Meeting large-scale restoration goals requires the connection between local seed production and collaborative platforms to negotiate roles, rights and responsibilities between stakeholders. An enduring native seed supply must include a diversity of voices and autonomy of community groups that builds equitable participation in social, economic, and environmental benefits.

A bee's eye view of remarkable floral colour patterns in the south-west Australian biodiversity hotspot revealed by false colour photography.

BACKGROUND AND AIMS: Colour pattern is a key cue of bee attraction selectively driving the appeal of pollinators. It comprises the main colour of the flower with extra fine patterns, indicating a reward focal point such as nectar, nectaries, pollen, stamens and floral guides. Such advertising of floral traits guides visitation by the insects, ensuring precision in pollen gathering and deposition. The study, focused in the Southwest Australian Floristic Region, aimed to spot bee colour patterns that are usual and unusual, missing, accomplished by mimicry of pollen and anthers, and overlapping between mimic-model species in floral mimicry cases. METHODS: Floral colour patterns were examined by false colour photography in 55 flower species of multiple highly diverse natural plant communities in south-west Australia. False colour photography is a method to transform a UV photograph and a colour photograph into a false colour photograph based on the trichromatic vision of bees. This method is particularly effective for rapid screening of large numbers of flowers for the presence of fine-scale bee-sensitive structures and surface roughness that are not detectable using standard spectrophotometry. KEY RESULTS: Bee- and bird-pollinated flowers showed the expected but also some remarkable and unusual previously undetected floral colour pattern syndromes. Typical colour patterns include cases of pollen and flower mimicry and UV-absorbing targets. Among the atypical floral colour patterns are unusual white and UV-reflecting flowers of bee-pollinated plants, bicoloured floral guides, consistently occurring in Fabaceae spp., and flowers displaying a selective attractiveness to birds only. In the orchid genera (Diuris and Thelymitra) that employ floral mimicry of model species, we revealed a surprising mimicry phenomenon of anthers mimicked in turn by model species. CONCLUSION: The study demonstrates the applicability of 'bee view' colour imaging for deciphering pollinator cues in a biodiverse flora with potential to be applied to other eco regions. The technique provides an exciting opportunity for indexing floral traits on a biome scale to establish pollination drivers of ecological and evolutionary relevance.

Seed encrusting with salicylic acid: A novel approach to improve establishment of grass species in ecological restoration.

To achieve global ambitions in large scale ecological restoration, there is a need for approaches that improve the efficiency of seed-based interventions, particularly in overcoming the bottleneck in the transition from germination to seedling establishment. In this study, we tested a novel seed-based application of the plant stress modulator compound salicylic acid as a means to reduce seedling losses in the seed-to-seedling phase. Seed coating technology (encrusting) was developed as a precursor for optimising field sowing for three grass species commonly used in restoration programs, Austrostipa scabra, Microlaena stipoides, and Rytidosperma geniculatum. Salicylic acid (SA, 0.1mM) was delivered to seeds via imbibition and seed encrusting. The effects of SA on seed germination were examined under controlled water-limited conditions (drought resilience) in laboratory setting and on seed germination, seedling emergence, seedling growth and plant survival in field conditions. Salicylic acid did not impact germination under water stress in controlled laboratory conditions and did not affect seedling emergence in the field. However, seedling survival and growth were improved in plants grown from SA treated seeds (imbibed and encrusted) under field conditions. When SA delivery methods of imbibing and coating were compared, there was no significant difference in survival and growth, showing that seed coating has potential to deliver SA. Effect of intraspecific competition as a result of seedling density was also considered. Seedling survival over the dry summer season was more than double at low seedling density (40 plants/m2) compared to high seedling density (380 plants/m2). Overall, adjustment of seeding rate according to expected emergence combined with the use of salicylic acid via coating could improve seed use efficiency in seed-based restoration.

Initiating pedogenesis of magnetite tailings using Lupinus angustifolius (narrow-leaf lupin) as an ecological engineer to promote native plant establishment.

Mine tailings pose physical and chemical challenges for plant establishment. Our aim was to learn from natural processes in long-term soil and ecosystem development to use tailings as novel parent materials and pioneer ecological-engineering plant species to ameliorate extreme conditions of tailings, and facilitate the establishment of subsequent native plants. A glasshouse trial was conducted using magnetite tailings containing various amendments, investigating the potential of the nitrogen (N)-fixing, non-native pioneer species Lupinus angustifolius (Fabaceae), narrow-leaf lupin, as a potential eco-engineer to promote soil formation processes, and whether amendment type or the presence of pioneer vegetation improved the subsequent establishment and growth of 40 species of native plants. We found that L. angustifolius eco-engineered the mine tailings, by enhancing the N status of tailings and mobilising primary mineral P into organic P via a carboxylate-exudation strategy, thereby enabling subsequent growth of native species. The substantial increases of the soil organic P (from ca. 10 to 150 mg kg-1) pool and organo-bound Al minerals (from 0 to 2 mg kg-1) were particularly evident, indicating the initiation of pedogenesis in mine tailings. Our findings suggest that the annual legume L. angustifolius has eco-engineering potential on mine tailings through N-fixation and P-mobilisation, promoting the subsequent growth of native plants. We proposed Daviesia (Fabaceae) species as native species alternatives for the non-native L. angustifolius in the Western Australian context. Our findings are important for restoration practitioners tasked with mine site restoration in terms of screening pioneer eco-engineering plant species, where native plants are required to restore after mine operations.

Plant scientists' research attention is skewed towards colourful, conspicuous and broadly distributed flowers.

Scientists' research interests are often skewed toward charismatic organisms, but quantifying research biases is challenging. By combining bibliometric data with trait-based approaches and using a well-studied alpine flora as a case study, we demonstrate that morphological and colour traits, as well as range size, have significantly more impact on species choice for wild flowering plants than traits related to ecology and rarity. These biases should be taken into account to inform more objective plant conservation efforts.

Ten golden rules for reforestation to optimize carbon sequestration, biodiversity recovery and livelihood benefits.

Urgent solutions to global climate change are needed. Ambitious tree-planting initiatives, many already underway, aim to sequester enormous quantities of carbon to partly compensate for anthropogenic CO2 emissions, which are a major cause of rising global temperatures. However, tree planting that is poorly planned and executed could actually increase CO2 emissions and have long-term, deleterious impacts on biodiversity, landscapes and livelihoods. Here, we highlight the main environmental risks of large-scale tree planting and propose 10 golden rules, based on some of the most recent ecological research, to implement forest ecosystem restoration that maximizes rates of both carbon sequestration and biodiversity recovery while improving livelihoods. These are as follows: (1) Protect existing forest first; (2) Work together (involving all stakeholders); (3) Aim to maximize biodiversity recovery to meet multiple goals; (4) Select appropriate areas for restoration; (5) Use natural regeneration wherever possible; (6) Select species to maximize biodiversity; (7) Use resilient plant material (with appropriate genetic variability and provenance); (8) Plan ahead for infrastructure, capacity and seed supply; (9) Learn by doing (using an adaptive management approach); and (10) Make it pay (ensuring the economic sustainability of the project). We focus on the design of long-term strategies to tackle the climate and biodiversity crises and support livelihood needs. We emphasize the role of local communities as sources of indigenous knowledge, and the benefits they could derive from successful reforestation that restores ecosystem functioning and delivers a diverse range of forest products and services. While there is no simple and universal recipe for forest restoration, it is crucial to build upon the currently growing public and private interest in this topic, to ensure interventions provide effective, long-term carbon sinks and maximize benefits for biodiversity and people.

E-greening the planet.

Ant Forest, a mobile app developed by the monolithic Alibaba Group, is greening individuals' daily activities and transforming human capacity to reverse global environmental degradation. Over 500 million e-trees are being cultivated every day in China using Ant Forest, and over 122 million real trees have been planted over more than 112 000 ha of degraded land. Ant Forest showcases how internet technology innovation combined with digital financing and philanthropy is contributing to solving environmental issues while attracting and retaining customer loyalty. This powerful business model has the potential to spread to all manner of environmental outcomes.

The potential for phosphorus benefits through root placement in the rhizosphere of phosphorus-mobilising neighbours.

Plants that produce specialised cluster roots, which mobilise large quantities of poorly available nutrients such as phosphorus (P), can provide a benefit to neighbouring plants that produce roots in the cluster rhizosphere, as demonstrated previously in pot studies. To be effective, such roots must be present within the short time of peak cluster activity. We tested if this requirement is met, and quantified potential P benefits, in a hyperdiverse Mediterranean woodland of southwest Australia where cluster-rooted species are prominent. Using minirhizotrons, we monitored root dynamics during the wet season in the natural habitat. We found non-cluster roots intermingling with all 57 of the observed cluster roots of the studied tree species, Banksia attenuata. Almost all (95%) of these cases were observed in a high-moisture treatment simulating the 45-year average, but not present when we intercepted some of the rainfall. We estimate that cluster-root activity can increase P availability to intermingling roots to a theoretical maximum of 80% of total P in the studied soil. Due to their high P-remobilisation efficiency (89%), which results from P rapidly being relocated from cluster roots within the plant, senesced Banksia cluster roots are a negligible P source for other roots. We conclude that, rather than serving as a P source, it is the cluster-root activity, particularly the exudation of carboxylates, that may improve the coexistence of interacting species that are capable of root intermingling, thus potentially promoting species diversity in nutrient-poor habitats, and that this mechanism will be less effective in a drying climate.

Structural Features of Carnivorous Plant (Genlisea, Utricularia) Tubers as Abiotic Stress Resistance Organs.

Carnivorous plants from the Lentibulariaceae form a variety of standard and novel vegetative organs and survive unfavorable environmental conditions. Within Genlisea, only G. tuberosa, from the Brazilian Cerrado, formed tubers, while Utricularia menziesii is the only member of the genus to form seasonally dormant tubers. We aimed to examine and compare the tuber structure of two taxonomically and phylogenetically divergent terrestrial carnivorous plants: Genlisea tuberosa and Utricularia menziesii. Additionally, we analyzed tubers of U. mannii. We constructed phylogenetic trees using chloroplast genes matK/trnK and rbcL and used studied characters for ancestral state reconstruction. All examined species contained mainly starch as histologically observable reserves. The ancestral state reconstruction showed that specialized organs such as turions evolved once and tubers at least 12 times from stolons in Lentibulariaceae. Different from other clades, tubers probably evolved from thick stolons for sect. Orchidioides and both structures are primarily water storage structures. In contrast to species from section Orchidioides, G. tuberosa, U. menziesii and U. mannii form starchy tubers. In G. tuberosa and U. menziesii, underground tubers provide a perennating bud bank that protects the species in their fire-prone and seasonally desiccating environments.

An ecological perspective on 'plant carnivory beyond bogs': nutritional benefits of prey capture for the Mediterranean carnivorous plant Drosophyllum lusitanicum.

BACKGROUND AND AIMS: Little is known about the evolutionary and ecological drivers of carnivory in plants, particularly for those terrestrial species that do not occur in typical swamp or bog habitats. The Mediterranean endemic Drosophyllum lusitanicum (Drosophyllaceae) is one of very few terrestrial carnivorous plant species outside of Australia to occur in seasonally dry, fire-prone habitats, and is thus an ecological rarity. Here we assess the nutritional benefits of prey capture for D. lusitanicum under differing levels of soil fertility in situ. METHODS: We measured the total nitrogen and stable nitrogen and carbon isotope ratios of D. lusitanicum leaves, neighbouring non-carnivorous plant leaves, and groups of insect prey in three populations in southern Spain. We calculated trophic enrichment (ε15N) and estimated the proportion of prey-derived nitrogen (%Nprey) in D. lusitanicum leaves, and related these factors to soil chemistry parameters measured at each site. KEY RESULTS: In all three populations studied, D. lusitanicum plants were significantly isotopically enriched compared with neighbouring non-carnivorous plants. We estimated that D. lusitanicum gain ~36 %Nprey at the Puerto de Gáliz site, ~54 %Nprey at the Sierra Carbonera site and ~75 %Nprey at the Montera del Torero site. Enrichment in N isotope (ε15N) differed considerably among sites; however, it was not found to be significantly related to log10(soil N), log10(soil P) or log10(soil K). CONCLUSIONS: Drosophyllum lusitanicum individuals gain a significant nutritional benefit from captured prey in their natural habitat, exhibiting proportions of prey-derived nitrogen that are similar to those recorded for carnivorous plants occurring in more mesic environments. This study adds to the growing body of literature confirming that carnivory is a highly beneficial nutritional strategy not only in mesic habitats but also in seasonally dry environments, and provides insights to inform conservation strategies for D. lusitanicum in situ.

Elucidating the surface geometric design of hydrophobic Australian Eucalyptus leaves: experimental and modeling studies.

Three Australian native Eucalyptus species, i.e., Eucalyptus woodwardii, Eucalyptus pachyphylla and Eucalyptus dolorosa, were investigated, for the first time, with respect to the hydrophobicity of their leaves. It is well established that these leaves exhibit exceptionally high water repellency, in addition to an extraordinary ability to retain water, albeit their specific wetting mechanisms are still poorly understood. To identify the critical factors underlying this phenomenon, the surface topography of these leaves was subjected to micro-examination (SEM). Micro- and nanometer scale surface roughness was revealed, resembling that of the quintessential "lotus effect". Surface free energy analysis was performed on two models based on the surface topographies of the study Eucalyptus species and lotus, in order to study wetting transitions on these specific microscopic surface features. The influence of surface geometrical parameters, such as edge-to-edge distance, base radius and cylindrical height, on surface free energy with different liquid penetration depths was studied with these two models. Larger energy barriers and smaller liquid-solid contact areas were more influential in the calculations for the lotus than for Eucalyptus. The information obtained from these two models may be useful for guiding the design of novel artificial surfaces in the collection and transport of micro-volume liquids.

Assessment of the Diversity of Fungal Community Composition Associated With Vachellia pachyceras and Its Rhizosphere Soil From Kuwait Desert.

This research examined the general soil fungi and AM fungal communities associated with a Lonely Tree species (Vachellia pachyceras) existing in the Sabah Al-Ahmad Natural Reserve located at the Kuwait desert. The goals of the study were to describe the general fungal and AM fungal communities present in the rhizospheric, non-rhizospheric soils and roots of V. pachyceras, respectively, as well as local and non-local V. pachyceras seedlings when grown under standard nursery growing environments. Soil and root samples were analyzed for an array of characteristics including soil physicochemical composition, and culture-independent method termed PCR-cloning, intermediate variable region of rDNA, the large subunit (LSU) and internal transcribed spacer (ITS) region sequence identifications. The results reveal that the fungal phylotypes were classified in four major fungal phyla namely Ascomycota, Basidiomycota, Chytridiomycota, and Zygomycota. The largest assemblage of fungal analyses showed communities dominated by members of the phylum Ascomycota. The assays also revealed a wealth of incertae sedis fungi, mostly affiliated to uncultured fungi from diverse environmental conditions. Striking difference between rhizosphere and bulk soils communities, with more fungal diversities and Operational Taxonomic Units (OTUs) richness associated with both the field and nursery rhizosphere soils. In contrast, a less diverse fungal community was found in the bulk soil samples. The characterization of AM fungi from the root system demonstrated that the most abundant and diversified group belongs to the family Glomeraceae, with the common genus Rhizophagus (5 phylotypes) and another unclassified taxonomic group (5 phylotypes). Despite the harsh climate that prevails in the Kuwait desert, studied roots displayed the existence of considerable number of AM fungal biota. The present work thus provides a baseline of the fungal and mycorrhizal community associated with rhizosphere and non-rhizosphere soils and roots of only surviving V. pachyceras tree from the Kuwaiti desert and seedlings under nursery growing environments.

Plastome-Wide Rearrangements and Gene Losses in Carnivorous Droseraceae.

The plastid genomes of four related carnivorous plants (Drosera regia, Drosera erythrorhiza, Aldrovanda vesiculosa, and Dionaea muscipula) were sequenced to examine changes potentially induced by the transition to carnivory. The plastid genomes of the Droseraceae show multiple rearrangements, gene losses, and large expansions or contractions of the inverted repeat. All the ndh genes are lost or nonfunctional, as well as in some of the species, clpP1, ycf1, ycf2 and some tRNA genes. Uniquely, among land plants, the trnK gene has no intron. Carnivory in the Droseraceae coincides with changes in plastid gene content similar to those induced by parasitism and mycoheterotrophy, suggesting parallel changes in chloroplast function due to the similar switch from autotrophy to (mixo-) heterotrophy. A molecular phylogeny of the taxa based on all shared plastid genes indicates that the "snap-traps" of Aldrovanda and Dionaea have a common origin.

Evaluating the diversity and composition of bacterial communities associated with Vachellia pachyceras - the only existing native tree species in the Kuwait desert.

We investigated the diversity and composition of bacterial communities in rhizospheric and non-rhizospheric bulk soils as well as root nodule bacterial communities of Vachellia pachyceras - the only native tree species existing in the Kuwait desert. Community fingerprinting comparisons and 16S rDNA sequence identifications were used for characterization of the bacterial population using specific primers. The bacterial characterization of soil samples revealed four major phyla: Acidobacteria, Bacteroidetes, Firmicutes, and Proteobacteria. In situ (desert) samples of both rhizospheric and non-rhizospheric bulk soil were dominated by the bacterial phyla Firmicutes and Bacteroidetes, whereas the phylum Betaproteobacteria was present only in non-rhizospheric bulk soil. Ex situ (nursery growing condition) V. pachyceras resulted in restricted bacterial communities dominated by members of a single phylum, Bacteroidetes. Results indicated that the soil organic matter and rhizospheric environments might drive the bacterial community. Despite harsh climatic conditions, data demonstrated that V. pachyceras roots harbor endophytic bacterial populations. Our findings on bacterial community composition and structure have major significance for evaluating how Kuwait's extreme climatic conditions affect bacterial communities. The baseline data obtained in this study will be useful and assist in formulating strategies in ecological restoration programs, including the application of inoculation technologies.

Geochemical and mineralogical constraints in iron ore tailings limit soil formation for direct phytostabilization.

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 (N2-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.