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Vegetation restoration of land post‐mining can strengthen the development of soil aggregates and promote the accumulation of soil organic carbon (SOC), and Microbial restoration such as Arbuscular mycorrhizal fungi (AMF) can significantly improve the effect of vegetation restoration. However, the effects of different recovery modes (microbial and natural restoration) on soil macroaggregates development and the carbon flows of the organic carbon (OC) have been less studied on reclaimed mine soil. A 4‐year field experiment was conducted on opencast coal reclaimed areas in Inner Mongolia grassland, and three recovery modes were set up: artificial restoration, artificial restoration (inoculated with AMF) and natural restoration. Results showed that compared with the natural restoration, artificial restoration and AMF inoculation increased the OC, total glomalin‐related soil proteins (TGRSP) contents and the value of δ13C in macroaggregates (>0.25 mm) in deep soil (30–50 cm). The shallow roots were the most likely starting points of carbon flow in the natural recovery area surface soil, and artificial restoration inoculation with AMF increased the carbon flows between all levels of aggregates in deep soil, showing a carbon flow pattern from macroaggregates to microaggregates (<0.25 mm). Moreover, significant correlations among the TGRSP, SOC content, and δ13C value were recorded, indicating the SOC sequestration and stability of reclaimed mine soil were potentially associated with TGRSP. In summary, both natural restoration and artificial restoration had advantages and disadvantages on reclaimed mine soil, but the artificial restoration inoculation with AMF showed great potential in promoting the aggregate carbon flow and persistent SOC accumulation. [ABSTRACT FROM AUTHOR]

Background: Arbuscular mycorrhizal fungi (AMF) are key soil organisms and their extensive hyphae create a unique hyphosphere associated with microbes actively involved in N cycling. However, the underlying mechanisms how AMF and hyphae-associated microbes may cooperate to influence N2O emissions from "hot spot" residue patches remain unclear. Here we explored the key microbes in the hyphosphere involved in N2O production and consumption using amplicon and shotgun metagenomic sequencing. Chemotaxis, growth and N2O emissions of isolated N2O-reducing bacteria in response to hyphal exudates were tested using in vitro cultures and inoculation experiments. Results: AMF hyphae reduced denitrification-derived N2O emission (max. 63%) in C- and N-rich residue patches. AMF consistently enhanced the abundance and expression of clade I nosZ gene, and inconsistently increased that of nirS and nirK genes. The reduction of N2O emissions in the hyphosphere was linked to N2O-reducing Pseudomonas specifically enriched by AMF, concurring with the increase in the relative abundance of the key genes involved in bacterial citrate cycle. Phenotypic characterization of the isolated complete denitrifying P. fluorescens strain JL1 (possessing clade I nosZ) indicated that the decline of net N2O emission was a result of upregulated nosZ expression in P. fluorescens following hyphal exudation (e.g. carboxylates). These findings were further validated by re-inoculating sterilized residue patches with P. fluorescens and by an 11-year-long field experiment showing significant positive correlation between hyphal length density with the abundance of clade I nosZ gene. Conclusions: The cooperation between AMF and the N2O-reducing Pseudomonas residing on hyphae significantly reduce N2O emissions in the microsites. Carboxylates exuded by hyphae act as attractants in recruiting P. fluorescens and also as stimulants triggering nosZ gene expression. Our discovery indicates that reinforcing synergies between AMF and hyphosphere microbiome may provide unexplored opportunities to stimulate N2O consumption in nutrient-enriched microsites, and consequently reduce N2O emissions from soils. This knowledge opens novel avenues to exploit cross-kingdom microbial interactions for sustainable agriculture and for climate change mitigation. C1gn2zbPQXat79TnoeAsNQ Video Abstract [ABSTRACT FROM AUTHOR]

Thermal infrared imaging technology was used to understand the effects of arbuscular mycorrhizal fungi (AMF) and dark septate endophytic (DSE) fungi, both separately and together, on plant growth and physiological status, and to screen and develop efficient microbial agents in a pot experiment design. Eight treatments comprised the control (CK), AMF inoculation alone, DSE fungal treatments (DSE20%, DSE40% and DSE80%; 2, 4, 8 × 105 CFU mL−1) and combined inoculation treatments (DSE20% + AMF, DSE40% + AMF, and DSE80% + AMF). Canopy temperature (Tcanopy) and stomatal conductance (gs) were monitored at different growth stages, and plant biomass-related indicators were obtained at harvest. These indicators were used to assess plant growth and the physiological status resulting from the different inoculation treatments. During plant growth, the plant Tcanopy decreased following inoculation. Differences in Tcanopy between control and inoculated plants were detected by thermal infrared imaging technology and were −3.8 to + 9.3 °C (control–inoculation treatment). Growth index and Tcanopy monitoring indicate that the growth-promoting effect of combined inoculation was higher than that of either fungal type alone, with DSE80% + AMF producing the highest growth promotion. During the growth process of inoculated maize, the effect of inoculated AMF on the physiological condition of maize growth can be better monitored by thermal infrared at 10 a.m., 12 p.m., 2 p.m. and 4 p.m. on the 31st–57th days of the growth period. The method and results of this experiment are conducive to the rapid and efficient monitoring of the effects of microorganisms on plant growth and physiological status and can be applied to the screening, application, and promotion of microbial agents. [ABSTRACT FROM AUTHOR]

Both indigenous arbuscular mycorrhizal (AM) fungi and phosphate solubilizing bacteria (PSB) are involved in phosphorus (P) mobilization and turnover in agroecosystems. Understanding the diversity and community structure of AM fungi and PSB is important for potentially optimizing their role in mining P for sustainable agriculture. Yet the characteristics of both AM fungi and PSB in response to P input, in particular the influence of different indigenous microbial communities on plant growth has been little studied. Here, we collected soil samples from the top 20 cm of the profile of a soil receiving three fertilizer P rates, comprising nil, optimal (44 kg P ha −1 ) and excessive (131 kg P ha −1 ) P to evaluate the AM fungal community structure and abundance of relevant PSB groups at three sampling times (June, July and September) using 454 pyrosequencing and quantitative-PCR (q-PCR), respectively. In addition, a pot experiment was conducted to investigate the feedback effects of different fractions of indigenous soil microbes on maize seedling growth. The results showed that overall sampling time had a greater impact than P application rate on the community structure of AM fungi and PSB abundance. At each sampling time the AM fungal communities were significantly affected by the fertilizer P rate. The overall abundance of soil microbes and selected taxa were slightly affected by sampling time but not by fertilizer P. Shoot biomass and P nutrition were significantly affected by the microbial community fraction but not by the fertilizer P rate. Changes in AM fungal communities did not lead to significant differences in maize growth. However, long-term absence of P inputs tended to build up microbial communities which greatly suppressed maize growth. Shoot biomass showed a mean decline of 24.4% when grown in inoculated soil compared to sterilized soil. Our results indicate that current P management has not led to negative influences on soil microbial communities. Evidence highlights the need to understand the interactions between plants and microbiome in mining P in order to make maximum use of the most effective indigenous soil microbes for sustainable agriculture. [ABSTRACT FROM AUTHOR]

A better understanding of Glomeromycotan biogeography is essential for the conservation of arbuscular mycorrhizal (AM) fungal species and the ecosystem services that they provide worldwide. Here, we examine the spatial dynamics of AM fungi along two slopes (4149 m a.s.l. to the summit at 5033 m a.s.l.) of Mount Mila on the Tibetan Plateau. Our hypothesis was that AM fungal communities at higher elevation would show distinct assemblages with lower diversity in conditions of increasing environmental harshness. A total of 52 operational taxonomic units (OTUs) spanning all four orders were detected and some OTUs were habitat specific. Nearly 30% of the OTUs were new phylotypes, including two family-like clades. Distinct communities of AM fungi were found at the higher elevation, demonstrating potential niche differentiation along the elevation gradient. Elevation patterns of taxon richness/diversity differed between the two transects, decreasing with increasing elevation on the eastern slope and unimodal (or no pattern) on the western slope. Taken together, we provide evidence for significant spatial structure of AM fungi across the elevation gradient, and the distribution patterns are regulated simultaneously by the plant communities, soil properties and climatic conditions in this plateau montane ecosystem. [ABSTRACT FROM AUTHOR]

Appropriate nitrogen (N) management is important to minimize N losses from intensively managed agricultural ecosystems. Understanding the community structure of arbuscular mycorrhizal fungi ( AMF) in response to N management can be of great ecological significance, particularly with the recent emphasis on the role of AMF in N cycling. A comprehensive study of both the vertical distribution of AMF in the soil profile and the temporal changes in community structure in maize roots was conducted over a 5-year period at a field site on the North China Plain. The N treatments consisted of zero N, conventional farming practice, and optimum N based on an in-season soil Nmin test. Terminal restriction fragment length polymorphism and clone sequencing were used to analyse the AMF community. Optimum N mitigated the decline in richness of AMF in the conventional N treatment in the surface soil. Diverse and species-rich AMF communities occurred deep in the soil profile. A significant difference in AMF community structure was observed between the control and fertilizer N treatments but not between the two N application strategies. AMF communities deeper in the soil profile were subsets of those richer communities in the surface soil and the loss of AMF taxa was mostly due to the absence of rare taxa. Soil pH and Nmin contents were major soil properties affecting the soil AMF communities among the N treatments while vertical distribution was influenced mainly by soil electrical conductivity. Crop phenology had a stronger influence than N treatment on the temporal shifts in AMF communities in maize roots. Our results provide evidence for the importance of N management in maintaining AMF diversity. Changes in soil chemical properties due to N fertilization, in particular declining soil pH, should be integrated in N management strategies to reduce the negative impacts on AMF communities induced by N fertilization. Excessive N inputs induced significant changes in soil physicochemical properties, especially soil acidification, and may have negative impacts on AMF communities. [ABSTRACT FROM AUTHOR]

• Vegetation restoration is essential to the development of cyanobacterial biocrusts. • Cyanobacterial biocrusts under N 2 -fixing plants had higher microbial biomass C:N:P estimates and AMF biodiversity. • Vegetation cover induced by revegetation type had direct positive effects on cyanobacterial biomass, the strongest driver of AMF diversity and microbial biomass C:P ratio. • N 2 -fixing plant restoration strategies are advisable in vegetation reconstruction. Vegetation restoration may promote the development of biological soil crusts (biocrusts) that are colonized by arbuscular mycorrhizal fungi (AMF) and play an important role in microbially-mediated mineral nutrient cycling. However, little is known about biocrust AMF communities or microbial biomass carbon (C), nitrogen (N) and phosphorus (P) cycling during vegetation restoration in coal mining subsidence areas. Here, we examine cyanobacterial biocrust microbial biomass C:N:P stoichiometry and AMF communities under five revegetation types, i.e., field plots planted with Hippophae rhamnoides , Xanthoceras sorbifolium , Cerasus humilis , Cerasus szechuanica , or Amorpha fruticosa. Cyanobacterial biocrusts under H. rhamnoides and A. futicosa had the highest estimated microbial biomass C:N:P and AMF α-diversity values but the lowest pH and electrical conductivity. Moreover, four AMF genera (Ambispora , Glomus , Diversispora , and Paraglomus), one order (Glomerales) and one class (Glomeromycetes) were the most abundant AMF in cyanobacterial biocrusts under the five revegetation types. Vegetation cover induced by revegetation type had direct positive effects on biocrust biomass and was the strongest driver of AMF diversity and microbial biomass C:P ratio. The N 2 -fixing plant species (A. fruticosa and H. rhamnoides) are preferable in restoration strategies in enhancing the development of cyanobacterial biocrusts and thus promoting the soil AMF community and microbial mineral nutrient cycling during vegetation reconstruction. The results provide a clearer understanding of the ecological functions of cyanobacterial biocrusts and further facilitate the assessment of ecosystem services and sustainable development in vegetation reconstruction in coal mining subsidence areas. [ABSTRACT FROM AUTHOR]

A field experiment was conducted to study the effects of inoculation with the arbuscular mycorrhizal fungus Glomus caledonium and/or Rhizobium meliloti on phytoremediation of an agricultural soil contaminated with weathered PCBs by alfalfa grown for 180 days. Planting alfalfa (P), alfalfa inoculated with G. caledonium (P+AM), alfalfa inoculated with R. meliloti (P+R), and alfalfa co-inoculated with R. meliloti and G. caledonium (P+AM+R) decreased significantly initial soil PCB concentrations by 8.1, 12.0, 33.8, and 43.5%, respectively. Inoculation with R. meliloti and/or G. caledonium (P+AM+R) increased the yield of alfalfa, and the accumulation of PCBs in the shoots. Soil microbial counts and the carbon utilization ability of the soil microbial community increased when alfalfa was inoculated with R. meliloti and/or G. caledonium. Results of this field study suggest that synergistic interactions between AMF and Rhizobium may have great potential to enhance phytoremediation by alfalfa of an agricultural soil contaminated with weathered PCBs. [ABSTRACT FROM AUTHOR]

A pot experiment investigated the response of two maize inbred lines with contrasting root morphology and phosphorus (P) efficiency to inoculation with Glomus mosseae or Glomus etunicatum compared with non-mycorrhizal controls. Soil phosphorus was supplied at rates of 10, 50, and 100 mg P kg -1 soil. Root length, specific root length, and specific phosphorus uptake of maize line 178 (P-efficient) were significantly higher than of line Hc (P-inefficient). Percentage of root length colonized showed the opposite trend regardless of soil P supply level. The two maize lines did not differ significantly in growth response to mycorrhizal colonization. Root colonization rate decreased with increasing soil phosphorus supply. The beneficial effect of the two AM fungi on plant growth and P uptake was greatest at low soil P level and the responses were negative at high P supply. Mycorrhizal responsiveness also decreased with increasing P supply and differed between the two mycorrhizal fungal isolates. [ABSTRACT FROM AUTHOR]

The influence of sulfur (S) supply and mycorrhizal colonization on the growth and pungency of spring onion (Allium fistulosum L.) seedlings grown for four months in Perlite and nutrient solution containing three levels of sulfate [0.1, 1.75, and 4 mM sulfate (SO42-)] were investigated. Plants were inoculated with Glomus etunicatum, Glomus intraradices, or Glomus mosseae, and uninoculated controls were included. Shoot and root dry weights of mycorrhizal and control plants supplied with 4 mM SO42+ were higher than with 0.1 or 1.75 mM SO42-. Enzyme produced pyruvic acid (EPY) and plant sulfur concentrations increased with increasing SO42- supply. The EPY and plant S concentrations were usually higher in mycorrhizal plants than controls irrespective of S supply, and shoot total S concentrations and EPY were strongly correlated. Arbuscular mycorrhizal colonization appeared to make a substantial contribution to the sulfur status of spring onion, and may thus have had a strong influence on its flavor characteristics. [ABSTRACT FROM AUTHOR]

A glasshouse pot experiment was conducted to investigate the impact of inoculation of cucumber at the germination stage with Glomus etunicatum BEG168 on plant yield and incidence of Fusarium oxysporum f.sp. cucumerinum inoculated 28 days after the start of the experiment. Inoculation with the AM fungus decreased both disease incidence and disease index. Mycorrhizal inoculation also increased P concentrations in the cucumber seedlings. The mycorrhizal seedlings had higher concentrations of proline and polyphenol oxidase activity but lower malondialdehyde than non-mycorrhizal seedlings, indicating that AM inoculation may have protected membrane permeability and reduced the extent of the damage caused by F. oxysporum . The results indicate that the mycorrhizal fungus may influence plant secondary metabolites and increase resistance to wilt disease in cucumber seedlings and may therefore have some potential as a biological control agent. [ABSTRACT FROM AUTHOR]

• Drought stress affected soybean growth and physiology. • Leaf temperature reflected the effect of AMF on plant water status under drought stress. • AMF regulated leaf temperature to affect other physiological activities. The influence of arbuscular mycorrhizal fungi (AMF) on plant water status and growth under drought stress were investigated using soybean subjected to drought stress (40% of soil water-holding capacity (WHC)) and control conditions (60% WHC) either inoculated with AMF or uninoculated controls. Leaf temperature (T leaf) and stomatal conductance (gs) were determined at 10:00, 12:00 and 18:00 on the harvest day. The effects of AMF on the water physiological status and growth of soybeans under drought stress were examined using thermal infrared imaging technology (TIIT). AMF inoculation under drought stress increased plant above- and below-ground biomass, nutritional status, and nitrogen, phosphorus and potassium uptake rates, and reduced plant root/shoot ratio. Monitoring T leaf reflected the effect of AMF on plant water physiological status under drought stress. AMF inoculation resulted in a decline in T leaf of 0.1–0.4 °C as water uptake proceeded compared with an increase of 0.2–1.4 °C in uninoculated controls. Thus, the effects of AMF on soybean drought resistance changed from positive to negative. AMF reduced plant T leaf , promoted the accumulation of photosynthetic products, reduced malondialdehyde accumulation, and increased stomatal regulation and T leaf. These preliminary results provide a basis for further studies on the effects of AMF on the water and growth status of plants under drought stress in arid areas. [ABSTRACT FROM AUTHOR]

• Revegetation types affected AMF communities and SOC fractions in mining reclamation. • Nitrogen-fixing plants could release soil nutrients to improve AMF community. • Soil pH, SOC and C:N ratio play a key role in shifting the AMF community. • AMF, revegetation types and SOC fractions had coupling biological relationship. The rhizosphere arbuscular mycorrhizal fungal (AMF) community and soil organic carbon (SOC) fractions are important in vegetation restoration because they can promote plant growth and environmental improvement in the mining subsidence area of northwest China. However, the effects of revegetation type on SOC fractions and the AMF community remain poorly understood despite their importance in promoting sustainable environmental development. Here, we have examined the rhizosphere soil AMF community and SOC fractions of five revegetation types comprising Amorpha fruticosa (AF), Hippophae rhamnoides (HR), Xanthoceras sorbifolium (XS), Cerasus humilis (CH), and Cerasus szechuanica (CS). Revegetation type significantly affected AMF α-diversity, communities and SOC fractions. The contents of soil microbial biomass carbon, dissolved organic carbon, readily oxidized organic carbon and readily extractable glomalin were maximum in HR. We found six genera of AMF (Glomus , Scutellospora , Paraglomus , Claroideoglomus , Ambispora and Diversispora) and Glomus was the most frequently occurring genus in each revegetation type. Nitrogen-fixing plants (AF and HR) may release large amounts of soil nutrients to promote the activity of the soil AMF community. Soil pH, SOC and C:N ratio play key roles in shifting the AMF community. Interactions between the soil AMF community and revegetation types are key to optimizing the restoration of degraded systems and accumulating soil organic matter. Our observations may provide fundamental guidelines in the assessment of ecosystem services and sustainable development in vegetation reconstruction in the coal mining subsidence areas. [ABSTRACT FROM AUTHOR]