Mycorrhizas and soil structure

Alleviating Plant Density and Salinity Stress in Moringa oleifera Using Arbuscular Mycorrhizal Fungi: A Review

Moringa oleifera (LAM) is a multipurpose tree species with extensive pharmacological and ethnomedicinal properties. Production of important medicinal plants is facing decline under changing climatic conditions, which brings along exacerbated abiotic stresses like salinity and intraspecific competition, particularly high planting densities. Increasing plant density is seen as a strategy to increase production; however, the intraspecific competition and a lack of arable land limit productivity. Salinity has been estimated to harm approximately six percent of the Earth's landmass. This leads to a loss of over 20% of agricultural output annually. These stressors can significantly curtail moringa's growth and yield potential. Literature designates that Arbuscular Mycorrhizal Fungi (AMF), ubiquitous soil microorganisms forming symbiotic associations with plant roots, offer a promising avenue for mitigating these stresses. This narrative review aims to investigate the utilization of AMF to alleviate the detrimental effects of salinity and high planting density on Moringa oleifera. The different adaptive strategies M. oleifera undergoes to mitigate both stressors are explored. The review found that AMF inoculation enhances plant tolerance to these stressors by improving nutrient acquisition, water relations, and activating stress response mechanisms. By facilitating improved nutrient and water absorption, AMF enhance root architecture, modulate ROS scavenging mechanisms, and promote optimal biomass allocation, ensuring better survival in high-density plantings. Furthermore, AMF-mediated stress alleviation is linked to enhanced physiological efficiency, including increased chlorophyll content, root-shoot biomass balance, and ion homeostasis. This review is important because it could provide insights into a sustainable, natural solution for improving the resilience of Moringa oleifera under adverse environmental conditions, with potential applications in global agriculture and food security. Future research should prioritize identifying and characterizing moringa-specific AMF species and evaluate the long-term efficacy, feasibility, and economic viability of AMF application in real-world moringa cultivation systems to fully harness the potential of AMF in moringa cultivation.

Microaggregates as Nutrient Reservoirs for Fungi Drive Natural Regeneration in Larch Plantation Forests

The natural regeneration of Larix gmelinii plantations plays a pivotal role in rehabilitating ecosystem services in Northeast China's degraded forests. However, mechanistic linkages between soil aggregate nutrient fluxes and fungal community assembly remain poorly constrained. Combining space-for-time substitution with particle-size fractionation and high-throughput sequencing, this study examined successional trajectories across regeneration in Langxiang National Nature Reserve to resolve nutrient-fungal interplay during long-term forest restructuring. The results demonstrated that microaggregates (<0.25 mm) functioned as nutrient protection reservoirs, exhibiting significantly higher total carbon (TC) and nitrogen (TN) contents and greater fungal diversity (p < 0.05). Both stand regeneration stage and aggregate size significantly influenced fungal community composition and structural organization (p < 0.05). Aggregate-mediated effects predominated in upper soil horizons, where fungal dominance progressively transitioned from Mortierellomycota to Ascomycota with increasing particle size. In contrast, lower soil layers exhibited regeneration-dependent dynamics: Basidiomycota abundance declined with L. gmelinii reduction, followed by partial recovery through mycorrhizal reestablishment in Pinus koraiensis broadleaf communities. Fungal co-occurrence networks displayed peak complexity during Juglans mandshurica germination (Node 50, Edge 345), with 64.6%positive correlations, indicating the critical period for functional synergy. Basidiomycota showed significant negative correlations with nutrients and major fungal phyla (R2 = 0.89). This study confirms that natural vegetation regeneration reshapes belowground processes through litter inputs and mycorrhizal symbiosis, while microaggregate management enhances soil carbon sequestration. Near-natural plantation management should incorporate broadleaf species to preserve mycorrhizal diversity and amplify ecosystem services. These findings provide an essential soil ecological theoretical basis for sustainable plantation management in Northeast China.

Impact of agricultural systems on arbuscular mycorrhizal fungi community composition in robusta coffee roots in the Democratic Republic of congo

Robusta coffee, grown by 25 million farmers across more than 50 countries, plays an important role in smallholder farmers' livelihoods and the economies of many low-income countries. Coffee establishes a mutualistic symbiosis with arbuscular mycorrhizal fungi (AMF); however, the impact of agricultural practices and soil characteristics on AMF diversity and community composition is not well understood. To address this, we characterised the AMF community composition of robusta coffee in part of its region of origin, the Democratic Republic of Congo. AMF diversity and community composition were compared between coffee monoculture, agroforestry systems and wild robusta in its native rainforest habitat. Using Illumina sequencing on 304 root samples, we identified 307 AMF operational taxonomic units (OTUs), dominated by the genera Glomus and Acaulospora. OTU richness did not vary across the three studied systems, yet large differences in community composition were found. Many unique OTUs were only observed in the coffee in the rainforest. In general, lower available soil phosphorus (P) and lower soil bulk density increased AMF diversity, yet higher available soil P and pH increased AMF diversity in the wild forest coffee. Shifts in AMF community composition across coffee systems were driven by canopy closure, soil pH, available soil P and soil bulk density. Our study is the first to characterise mycorrhizal communities in wild robusta coffee in its region of origin and shows that even low-input agricultural practices result in major AMF community shifts as compared to a natural baseline.

Enriched anoxic methanotrophic consortium augmentation for mitigating methane emissions in rainfed systems and climate-neutral rice production

This study demonstrated the effectiveness of enriched anoxic methanotrophic consortium augmentation in reducing methane (CH4) emissions from rice cultivation while improving soil fertility and rice productivity. The enriched consortium from cattle farm effluent, dominated by Acinetobacter (65.5%) and containing both types I (Methylosarcina, Methylomagnum, and Methyloversatilis) and II (Methylocystis) methanotrophs, exhibited high methane oxidation rates (Vmax 45.70 ± 13.71 μmol-CH4⋅g-1⋅h-1 and Km 16.50 ± 4.95 μM). The optimal inoculum size for soil application was 0.2 L⋅m-2 (OD600 = 0.5), resulting in a CH4 reduction efficiency of 74.30 ± 3.56%. In rice pot experiments, the anoxic methanotrophic consortium with an inoculum size of 0.2 L⋅m-2 reduced methane emissions by 79.32 ± 3.96% without fertilizer and 29.22 ± 1.45% and 46.81 ± 1.87% when combined with organic and chemical fertilizers, respectively. The field-scale evaluation revealed that combined soil and irrigation water application with anoxic methanotrophic consortium augmentation was the most effective, reducing seasonal methane emissions from 32.8 ± 4.2 to 9.3 ± 1.5 g-CH4·m-2 and methane flux from 15.2 ± 2.1 to 4.3 ± 0.8 mg-CH4·m-2·h-1, representing a 71.7 ± 0.4% reduction. This method also increased plant height (6.5%) and tiller number (26.4%). The combined application method also resulted in the highest soil nutrient levels (96.1 mg-N·kg-1 soil, 21.8 mg-P·kg-1 soil, and 133.4 mg-K·kg-1 soil) and increased rice yield by 14.7% (975 g⋅m-2). These findings demonstrate that anoxic methanotrophic consortium augmentation is a sustainable approach to mitigate methane emissions and improve rice productivity, emphasizing the importance of integrating this strategy into rice cultivation practices in rainfed lowland areas.

Microbial inoculants - fostering sustainability in groundnut production

Groundnut (Arachis hypogaea L.) is a vital leguminous oilseed crop, widely cultivated in tropical and subtropical regions due to its high nutritional and economic significance in food, feed, and oil purposes. It is a rich source of protein, oil, vitamins, minerals, and bioactive compounds with anti-inflammatory, anticancer, and anti-aging properties. Globally, groundnut production is approximately 54.2 million tonnes, with India contributing 10.1 million tonnes through rainfed cultivation. However, its productivity is constrained by drought, salinity, soil nutrient deficits, and disease infestations. Conventional farming depends on chemical inputs to enhance yield and productivity but negatively impacts soil health and fertility, reduces microbial diversity, and pollutes agroecosystems, creating an urgent need for sustainable alternatives. Microbe-based bioinoculants comprising nitrogen-fixers, phosphorus solubilizers, potassium solubilizers, sulphur oxidizers, other plant growth-promoting rhizobacteria (PGPR), mycorrhizal fungi, and cyanobacteria offer an alternative approach to enhance the growth and yield of groundnut through various direct and indirect mechanisms, including augmenting nutrient absorption, improving quality parameters, suppressing plant pathogens, stimulating plant defence, and increasing resilience to abiotic stresses. This narrative review examines the diversity, benefits, and growth-promoting mechanisms of rhizospheric, phyllospheric, and endophytic microorganisms associated with groundnut. Additionally, molecular docking of groundnut root exudate metabolites, produced upon microbial inoculation, with stress-responsive proteins highlights the significance of microbial inoculants in mitigating drought and salinity stresses. This review synthesizes recent advances in microbial inoculant applications, highlighting their potential to revolutionize sustainable groundnut cultivation. Therefore, microbial inoculants provide a promising solution ensuring sustainability and assurance of food security amid global difficulties.

Advances, Challenges, and Perspectives in Glomalin-Related Soil Protein Research

Glomalin-related soil protein (GRSP), a glycoprotein primarily exuded by arbuscular mycorrhizal fungi (AMF), exerts key roles in ecological processes in terrestrial ecosystems. Nevertheless, the intricate nature of GRSP, coupled with constraints in its extraction and analytical methodologies, impedes a comprehensive understanding of its compositional attributes and ecological functions. Moreover, the scope of current GRSP research has undergone significant expansion, necessitating a comprehensive synthesis in this field. Here, we employed bibliometric analysis to systematically assess research trends and hotspots in the research field of GRSP based on 840 relevant articles indexed in the Web of Science Core Collection database. Among them, key parameters evaluated encompass publications' quantity, highly cited articles, high-frequency keywords, and historical direct citations. These analyses illuminated the state-of-the-art of GRSP research, delineated emergent trends, and provided future perspectives. Current investigations into GRSP predominantly focus on three major topics: (i) GRSP's nature, origin, and quantification methodologies; (ii) GRSP's key influencing factors including agricultural management practices, climate and land use change; and (iii) GRSP's ecological functions enhancing soil aggregate stability, C sequestration, and contamination remediation. Our findings can serve as a scholarly resource for advancing inquiries into the ecological functionalities of GRSP and its prospective applications in sustainable soil management and ecological restoration.

Root separation modulates AMF diversity and composition in tomato-potato onion intercropping systems

Plant-plant interactions shape arbuscular mycorrhizal fungi (AMF) communities in rhizosphere soil, with tomato/potato-onion intercropping emerging as a promising agro-ecological strategy to optimize resource utilization. However, the role of root separation methods in modulating AMF diversity within intercropping systems remains unclear. Specifically, whether the AMF community in the rhizosphere of tomato and potato-onion intercropping differs from monoculture and how root separation methods modulate these effects. This study evaluates the effects of various root separation methods (no separation, 0.45 μm nylon membrane, 38 μm nylon membrane, and solid separation) on AMF diversity and composition in tomato/potato-onion intercropping and monoculture systems. High-throughput Illumina MiSeq sequencing was used to assess AMF diversity indices (Ace, Chao1, Shannon, and Simpson), and Principal Coordinate Analysis evaluated community structure. Results showed that the non-separation mode achieved the highest Ace and Chao1 indices, indicating greater richness, while intercropping lowered Shannon and Simpson indices. Intercropping significantly reduced Glomerales but increased Paraglomerales, under the non-separation mode. Similarly, it decreased Glomus while increasing Paraglomus in the rhizosphere of both crops. Principal Coordinate Analysis revealed that root separation distinctly altered AMF community structure, reflecting specific barrier effects on AMF interactions. Intercropping increased AMF abundance in the tomato rhizosphere but reduced it in potato-onion as shown by 18S rRNA gene abundance. These findings emphasize that minimizing root separation in intercropping enhances AMF diversity and functionality, providing valuable insights for sustainable agricultural management. Understanding the role of root interactions in shaping AMF communities can help optimizing intercropping strategies to improve soil health and nutrient dynamics.

Although invisible, fungi are recognized as the engines of a microbial powerhouse that drives soil ecosystem services

Soil ecosystem services (SES) are the benefits that humans derive from soil. These services emerge from the complex interactions between biotic and abiotic processes within soil systems. They are vital for maintaining ecosystem resilience and ensuring long-term sustainability. Soil hosts a diverse group of biota, among them fungi play a crucial role in supporting and enhancing SES due to their remarkable adaptability and ability to thrive under unfavorable conditions. This review explores the multifaceted roles of fungi in SES, emphasizing their growing importance in strengthening ecosystem resilience and climate change adaptation. Fungi significantly contribute to the key ecosystem processes such as soil aggregation, organic matter (OM) decomposition, nutrients cycling, plant productivity, and carbon (C) sequestration. However, potential threats to fungal abundance and diversity could undermine these critical functions, highlighting the need for proactive measures to preserve fungal communities. The pivotal role of fungi in SES, including agricultural production and climate regulation, tailor them as indispensable microbial engines that shape and maintain ecosystem resilience. Emerging evidence suggests that soil fungal communities may become increasingly prominent under the future climate scenarios. Thus, understanding how fungal functional roles evolve in response to climate change is emergent for safeguarding SES and ensuring environmental sustainability. Furthermore, the co-occurrance of fungi with other soil organisms in supporting SES highlights the need to integrate diverse soil biota alongside fungi to promote sustainable SES. Collaborative efforts to comprehend and manage soil microbial communities are imperative for maintaining the long-term ecological stability of ecosystems.

Higher Plant Diversity Does Not Moderate the Influence of Changing Rainfall Regimes on Plant-Soil Feedback of a Semi-Arid Grassland

Climate change is expected to increase the frequency of severe droughts, but it remains unclear whether soil biotic conditioning by plant communities with varying species richness or functional group diversity moderate plant-soil feedback (PSF)-an important ecosystem process driving plant community dynamics-under altered rainfall regimes. We conducted a two-phase PSF experiment to test how plant diversity affects biotic PSF under different rainfall regimes. In Phase 1, we set up mesocosms with 15 plant assemblages composed of two grasses, two forbs and two nitrogen-fixing legumes [one, two, three, or six species from one, two, or three functional group(s)] common to the semi-arid eastern Eurasian Steppe. Mesocosms were subjected to two rainfall amounts (ambient, 50% reduction) crossed with two frequencies (ambient, 50% reduction) for a growing season (~3 months). Conditioned soil from each mesocosm was then used in Phase 2 to inoculate (7% v/v) sterilised mesocosms planted with the same species as in Phase 1 and grown for 8 weeks. Simultaneously, the same plant assemblages were grown in sterilised soil to calculate PSF based on plant biomass measured at the end of Phase 2. Feedback effects differed amongst plant assemblages, but were not significantly altered by reduced rainfall treatments within any plant assemblage. This suggests that the examined interactions between plant and soil microbial communities were resistant to simulated rainfall reductions and that increasing plant diversity did not moderate PSF under altered rainfall regimes. Moreover, increasing plant species richness or functional group diversity did not lessen the magnitude of PSF differences between ambient and reduced rainfall treatments. Collectively, these findings advance our understanding of plant diversity's potential to mitigate climate change effects on PSF, showing that in semi-arid grasslands, higher plant diversity may not moderate PSF responses to altered rainfall regimes and highlighting the importance of considering species-specific traits and interaction stability.

Enhancing consistency in arbuscular mycorrhizal trait-based research to improve predictions of function

Arbuscular mycorrhizal (AM) fungi (phylum Glomeromycota) are obligate symbionts with plants influencing plant health, soil a(biotic) processes, and ecosystem functioning. Despite advancements in molecular techniques, understanding the role of AM fungal communities on a(biotic) processes based on AM fungal taxonomy remains challenging. This review advocates for a standardized trait-based framework to elucidate the life-history traits of AM fungi, focusing on their roles in three dimensions: host plants, soil, and AM fungal ecology. We define morphological, physiological, and genetic key traits, explore their functional roles and propose methodologies for their consistent measurement, enabling cross-study comparisons towards improved predictability of ecological function. We aim for this review to lay the groundwork for establishing a baseline of AM fungal trait responses under varying environmental conditions. Furthermore, we emphasize the need to include underrepresented taxa in research and utilize advances in machine learning and microphotography for data standardization.

Evaluating the effectiveness of Pisolithus tinctorius in enhancing the Eucalyptus' resistance to salt stress

Afforestation projects on saline land, using Eucalyptus trees and ectomycorrhizal fungi, are crucial for restoring affected areas and promoting ecological and economic benefits, particularly in saline-affected areas. This study was conducted to isolate Pisolithus sp. and estimate its potential to improve the growth performance of Eucalyptus globulus seedlings under salt-stress conditions. Pisolithus sp. was isolated from mature sporocarps and identified through 18S rDNA. Pisolithus sp. was evaluated for its response to varying pH values, temperatures, and salinity levels. A pot experiment was conducted to assess the Pisolithus strain's effectiveness in reducing soil salinity's impact on the growth of Eucalyptus globulus seedlings in sandy soil. The identified Pisolithus tinctorius with an accession number of OM125275 revealed the highest mycelium dry weight of 0.09 g/100 ml medium at pH 5.8, 0.08 g/100 ml medium at 28 °C, and 0.12 g/100 ml medium at 4% NaCl. Eucalyptus globulus seedlings inoculated with Pisolithus tinctorius demonstrated significant improvement in most parameters compared to non-mycorrhizal (control) seedlings under salt stress. The seedlings inoculated with Pisolithus tinctorius and irrigated with 6 dS/m saline water revealed the highest shoot height (55.670 cm), root length (42.33 cm), shoot fresh weight (6.44 g/plant), root fresh weight (1.84 g/plant), shoot dry weight (2.37 g/plant), and root dry weight (0.810 g/plant) when compared to all treatments. Our findings suggest that selecting appropriate fungal strains is crucial for improving plant performance in saline conditions.

Optimizing cover crop practices as a sustainable solution for global agroecosystem services

The practice of cover crops has gained popularity as a strategy to improve agricultural sustainability, but its full potential is often limited by environmental trade-offs. Using meta-analytic and data-driven quantifications of 2302 observations, we optimized cover crop practices and evaluated their benefits for global agroecosystems. Cover crops have historically boosted crop yields, soil carbon storage, and stability, but also stimulated greenhouse gas emissions. However, combining them with long-term implementation (five years or more) and climate-smart practices (such as no-tillage) can enhance these services synergistically. A biculture of legume and non-legume cover crops, terminated 25 days before planting the next crop and followed by residue mulching, is the optimal portfolio. Such optimized practices are projected to increase agroecosystem multiservices by 1.25%, equivalent to annual gains of 97.7 million metric tons in crop production, 21.7 billion metric tons in carbon dioxide sequestration, and 2.41 billion metric tons in soil erosion reduction. By 2100, the continued implementation of optimized practices could mitigate climate-related yield losses and contribute to climate neutrality and soil stabilization, especially in harsh and underdeveloped areas. These findings underscore the promising potential of optimized cover crop practices to achieve the synergy in food security and environmental protection.

Polypropylene microfibers negatively affect soybean growth and nitrogen fixation regardless of soil type and mycorrhizae presence

Recent studies have indicated that soil contamination with microplastics (MPs) can negatively affect agricultural productivity, although these effects vary greatly depending on the context. Furthermore, the mechanisms behind these effects remain largely unknown. In this study, we examined the impact of two concentrations of polypropylene (PP) fibers in the soil (0.4 % and 0.8 % w/w) on soybean growth, nitrogen uptake, biological nitrogen fixation (BNF), and water use efficiency by growing plants in two soil types, with and without arbuscular mycorrhizal fungi (AMF). PP contamination consistently reduced vegetative growth (-12 %, on average compared to the control), with the severity of this effect varying significantly by soil type (more pronounced in Alfisol than in Vertisol). The extent of BNF progressively reduced with the increase in PP contamination level in both soils (on average, -17.1 % in PP0.4 and -27.5 % in PP0.8 compared to the control), which poses clear agro-environmental concerns. Water use efficiency was also reduced due to PP contamination but only in the Alfisol (-9 %, on average). Mycorrhizal symbiosis did not seem to help plants manage the stress caused by PP contamination, although it did lessen the negative impact on BNF. These findings are the first to demonstrate the effect of PP on BNF in soybean plants, underscoring the need to develop strategies to reduce PP pollution in the soil and to mitigate the impact of PP on the functionality and sustainability of agroecosystems.

A state-of-the-art review of environmental behavior and potential risks of biodegradable microplastics in soil ecosystems: Comparison with conventional microplastics

As the use of biodegradable plastics becomes increasingly widespread, their environmental behaviors and impacts warrant attention. Unlike conventional plastics, their degradability predisposes them to fragment into microplastics (MPs) more readily. These MPs subsequently enter the terrestrial environment. The abundant functional groups of biodegradable MPs significantly affect their transport and interactions with other contaminants (e.g., organic contaminants and heavy metals). The intermediates and additives released from depolymerization of biodegradable MPs, as well as coexisting contaminants, induce alterations in soil ecosystems. These processes indicate that the impacts of biodegradable MPs on soil ecosystems might significantly diverge from conventional MPs. However, an exhaustive and timely comparison of the environmental behaviors and effects of biodegradable and conventional MPs within soil ecosystems remains scarce. To address this gap, the Web of Science database and bibliometric software were utilized to identify publications with keywords containing biodegradable MPs and soil. Moreover, this review comprehensively summarizes the transport behavior of biodegradable MPs, their role as contaminant carriers, and the potential risks they pose to soil physicochemical properties, nutrient cycling, biota, and CO2 emissions as compared with conventional MPs. Biodegradable MPs, due to their great transport and adsorption capacity, facilitate the mobility of coexisting contaminants, potentially inducing widespread soil and groundwater contamination. Additionally, these MPs and their depolymerization products can disrupt soil ecosystems by altering physicochemical properties, increasing microbial biomass, decreasing microbial diversity, inhibiting the development of plants and animals, and increasing CO2 emissions. Finally, some perspectives are proposed to outline future research directions. Overall, this study emphasizes the pronounced effects of biodegradable MPs on soil ecosystems relative to their conventional counterparts and contributes to the understanding and management of biodegradable plastic contamination within the terrestrial ecosystem.

Delayed Sowing Reduced Verticillium Wilt by Altering Soil Temperature and Humidity to Enhance Beneficial Rhizosphere Bacteria of Sunflower

Sunflower Verticillium Wilt (SVW) caused by Verticillium dahliae is a significant threat to sunflower production in China. This soilborne disease is difficult to control. It has been observed that delayed sowing reduces the severity of SVW on different varieties and across various locations. Soil was collected from multiple locations with different sowing dates to understand the underlying biological mechanisms driving this phenomenon. The soil bacterial community was characterized through 16S rRNA gene amplicon sequencing performed on the Illumina MiSeq platform, followed by comprehensive bioinformatics analysis. Microsclerotia numbers in soil were detected using both NP-10 selective medium and quantitative polymerase chain reaction (qPCR). By delaying the sowing date, the number of microsclerotia in soil and the biomass of V. dahliae colonized inside sunflower roots were reduced during the early developmental stages (V2-V6) of sunflowers. Amplicon sequencing revealed an increased abundance of bacterial genera, such as Pseudomonas, Azoarcus, and Bacillus in soil samples collected from delayed sowing plots. Five bacterial strains isolated from the delayed sowing plot exhibited strong antagonistic effects against V. dahliae. The result of the pot experiments indicated that supplying two different synthetic communities (SynComs) in the pot did increase the control efficiencies on SVW by 19.08% and 37.82% separately. Additionally, soil temperature and humidity across different sowing dates were also monitored, and a significant correlation between disease severity and environmental factors was observed. In conclusion, delayed sowing appears to decrease microsclerotia levels by recruiting beneficial rhizosphere bacteria, thereby reducing the severity of SVW.

Grassland degraded patchiness reduces microbial necromass content but increases contribution to soil organic carbon accumulation

Plant and microbially derived carbon (C) are the two major sources of soil organic carbon (SOC), and their ratio impacts SOC composition, accumulation, stability, and turnover. The contributions of and the key factors defining the plant and microbial C in SOC with grassland patches are not well known. Here, we aim to address this issue by analyzing lignin phenols, amino sugars, glomalin-related soil proteins (GRSP), enzyme activities, particulate organic carbon (POC), and mineral-associated organic carbon (MAOC). Shrubby patches showed increased SOC and POC due to higher plant inputs, thereby stimulating plant-derived C (e.g., lignin phenol) accumulation. While degraded and exposed patches exhibited higher microbially derived C due to reduced plant input. After grassland degradation, POC content decreased faster than MAOC, and plant biomarkers (lignin phenols) declined faster than microbial biomarkers (amino sugars). As grassland degradation intensified, microbial necromass C and GRSP (gelling agents) increased their contribution to SOC formation. Grassland degradation stimulated the stabilization of microbially derived C in the form of MAOC. Further analyses revealed that microorganisms have a C and P co-limitation, stimulating the recycling of necromass, resulting in the proportion of microbial necromass C in the SOC remaining essentially stable with grassland degradation. Overall, with the grassland degradation, the relative proportion of the plant component decreases while than of the microbial component increases and existed in the form of MAOC. This is attributed to the physical protection of SOC by GRSP cementation. Therefore, different sources of SOC should be considered in evaluating SOC responses to grassland degradation, which has important implications for predicting dynamics in SOC under climate change and anthropogenic factors.

Garlic stalk waste and arbuscular mycorrhizae mitigate challenges in continuously monocropping eggplant obstacles by modulating physiochemical properties and fungal community structure

BACKGROUND AND AIMS

Continuous vegetable production under plastic tunnels faces challenges like soil degradation, increased soil-borne pathogens, and diminished eggplant yield. These factors collectively threaten the long-term sustainability of food security by diminishing the productivity and resilience of agricultural soils. This research examined the use of raw garlic stalk (RGS) waste and arbuscular mycorrhizal fungi (AMF) as a sustainable solution for these issues in eggplant monoculture. We hypothesized that the combined application of RGS waste and AMF would improve soil physicochemical properties compared to untreated soil in eggplant monoculture. The combined use of RGS and AMF was expected to suppress soil-borne pathogens, increase the abundance of soil beneficial microorganisms and alter fungal community structure. The combined application of RGS and AMF will significantly enhance eggplant yield compared to untreated plots. This study aimed to determine whether AMF and RGS, individually or in combination, can ameliorate the adverse effects of monoculture on eggplant soil. We also investigated whether these treatments could enhance eggplant yield.

METHODS

The experiment was arranged in a completely randomized design with four treatments: AMF, RGS, and a combined treatment of AMF + RGS (ARGS), along with a control. Each treatment was replicated three times, Eggplant seedlings inoculated with AMF and treated with RGS amendments, both individually and combined. The effects on root traits, soil physicochemical properties, soil enzyme activity, and fungal community structure were investigated.

RESULTS

RGS amendments and AMF inoculation improved root length, volume, and mycorrhizal colonization. The combined treatment showed the most significant improvement. RGS and AMF application increased soil nutrient availability (N, P, K) and organic matter content. Enzyme activities also increased with RGS and AMF treatments, with the combined application showing the highest activity. Soil electrical conductivity (EC) increased, while soil pH decreased with RGS and AMF amendments. Sequencing revealed a shift in the fungal community structure. Ascomycota abundance decreased, while Basidiomycota abundance increased with RGS and AMF application. The combined treatment reduced the abundance of pathogenic genera (Fusarium) and enriched beneficial taxa (Chaetomium, Coprinellus, Aspergillus). Pearson correlations supported the hypothesis that soil physicochemical properties influence fungal community composition.

CONCLUSIONS

This study demonstrates the potential of co-applying RGS and AMF in continuous cropping systems. It enhances soil physicochemical properties, reduces soil-borne pathogens, and promotes beneficial microbial communities and eggplant yield. This combined approach offers a sustainable strategy to address the challenges associated with eggplant monoculture under plastic tunnels.

Mycorrhizal status regulates plant phenological mismatch caused by warming

Mycorrhiza is an important functional feature of plants, which plays a vital role in regulating plant phenology in response to environmental changes. However, the effect of mycorrhiza on plant phenological asymmetry in response to climate changes is still rarely reported. Based on a global database of mycorrhizal statuses (obligately mycorrhizal, OM and facultatively mycorrhizal, FM) and phenology, we demonstrated that mycorrhizas reduce the phenological mismatches between above- and below-ground plant responses to climate warming under OM status. The mismatch of above- and below-ground growing season length of FM plants to warming was as high as 10.65 days, 9.1925 days and 12.36 days in total, herbaceous and woody plants, respectively. The mismatch of growing season length of OM plants was only 2.12 days, -0.61 days and 7.64 days among plant groups, which was much lower than that of FM plants. Correlation analysis indicated that OM plants stabilized plant phenology by regulating the relationship between the start of the growing season and the length of the growing season. Path analysis found that herbaceous plants and woody plants reduced phenological mismatches by stabilizing below-ground and above-ground phenology, respectively. In exploring the effects of mycorrhizal status on early- or late-season phenophases, we found that different mycorrhizal statuses affected the response of early- or late-season phenophase to warming. OM promoted the advance of early-season phenophase, and FM promoted the delay of late-season phenophase among different plant groups. In different regions, OM and FM promoted the advance of early-season phenophase in temperate and boreal regions, respectively. Our results indicate that mycorrhizal status mediates plant phenological response to warming, so the potential effects of mycorrhizal status should be considered when studying plant phenology changes.

Fungal necromass contribution to carbon sequestration in global croplands: A meta-analysis of driving factors and conservation practices

Fungal necromass carbon (FNC) contributes significantly to the build-up of soil organic carbon (SOC) by supplying abundant recalcitrant polymeric melanin present in the fungal cell wall. However, the influence of a wide range of conservation practices and associated factors on FNC accumulation and contribution to SOC in global croplands remains unexplored. Here, a meta-analysis was performed using 873 observations across three continents, together with structural equation modeling, to evaluate conservation practices and factors responsible for the enhancement of FNC and SOC. FNC content (8.39 g kg-1) of North American soils was highest compared to FNC content of Asian and European soils. The structural equation models showed a significant (p < 0.05) positive influence of microbial biomass carbon (MBC), soil pH, and clay contents on the accumulation of FNC. Soil C/N ratio and climate factors, however, had only minor influences on FNC accumulation. Notably, the main driver of FNC was MBC, which is mainly influenced by the soil total N and geographic factors in the study areas. Typical 5 cropland practices had significant effect size (p < 0.05) on FNC, leading to an increase of 12 % to 26 %, and the FNC content was greatest under straw amendment (26 %). Fungal necromass accumulation efficiency ranged from 23 % to 45 % depending on cropland practices: non- and reduced tillage was the most efficient (45 %), followed by crop coverage (32 %), straw amendment (30 %), and manure application (27 %), while N fertilization had the lowest efficiency (23 %). We conclude that FNC contributes to over a quarter of SOC, highlighting its major role in enhancing C sequestration worldwide. Conservation practices, particularly non-tillage or reduced tillage, are important to enhance C sequestration from FNC in croplands.

Fungal community determines soil multifunctionality during vegetation restoration in metallic tailing reservoir

Microorganisms are pivotal in sustaining soil functions, yet the specific contributions of bacterial and fungal succession on the functions during vegetation restoration in metallic tailing reservoirs remains elusive. Here, we explored bacterial and fungal succession and their impacts on soil multifunctionality along a ∼50-year vegetation restoration chronosequence in China's largest vanadium titano-magnetite tailing reservoir. We found a significant increase in soil multifunctionality, an index comprising factors pertinent to soil fertility and microbially mediated nutrient cycling, along the chronosequence. Despite increasing heavy metal levels, both bacterial and fungal communities exhibited significant increase in richness and network complexity over time. However, fungi demonstrated a slower succession rate and more consistent composition than bacteria, indicating their relatively higher resilience to environmental changes. Soil multifunctionality was intimately linked to bacterial and fungal richness or complexity. Nevertheless, when scrutinizing both richness and complexity concurrently, the correlations disappeared for bacteria but remained robust for fungi. This persistence reveals the critical role of the fungal community resilience in sustaining soil multifunctionality, particularly through their stable interactions with powerful core taxa. Our findings highlight the importance of fungal succession in enhancing soil multifunctionality during vegetation restoration in metallic tailing reservoirs, and manipulating fungal community may expedite ecological recovery of areas polluted with heavy metals.

Stability and heavy metals accumulation of soil aggregates under different land uses in the southwest coastal Bangladesh

Agricultural soil contamination is increasing day-by-day and becoming a major problem over the globe. Trace elements accumulation in the bulk soil is frequently documented, however, there is no precise mechanism of their distribution in the different soil aggregates level. We collected twelve composite soil samples from banana fields, fallow land, rice cultivated with pond water (rice field-I), and rice cultivated with rain water (rice field-II). We separated soil samples into four different size of aggregates (4-2, 2-0.25, 0.25-0.053, <0.053-mm) and then, aggregate stability (MWD), soil organic carbon (SOC), and heavy metals content (Pb, Cd, Cr, As, Fe, Mn, Zn, Ni, Co, Cu) in the soil samples were measured with different techniques. Results showed that MWD was higher in the rice-based land use, which was significantly contributed by SOC (p < 0.001). The concentration of Pb, As, Cd, Fe, and Mn were increased, while Cu and Zn concentration were reduced with increasing aggregate size (p < 0.05). In contrast, aggregate size did not influence on Ni and Co accumulation (p > 0.05). Moreover, macroaggregate acted as an accumulator for Fe, Mn, and As, while all the aggregate fractions acted as accumulators for Cu and Zn. Our study indicated that MWD, SOC, aggregate size and composition, and metal species were the controlling factors of trace elements accumulation and distribution in the various sizes of soil aggregates.

Impact of zinc on arbuscular mycorrhizal-mediated nutrient acquisition in urban horticulture

A major barrier to sustainably improving food security for a growing global population is the availability of suitable space for growing crops. Urban areas offer a potential solution to increase availability of land, however, horticultural soils often accumulate zinc. These increased levels may affect the interactions between crops and soil microbes with potential implications for crop health and nutrition. Using radio-isotope tracing, we investigated the effect of urban environmentally relevant concentrations of zinc in soils on the nutrient exchange between arbuscular mycorrhizal fungi and pea plants. At higher concentrations of zinc, transfer of phosphorus from fungi to plants and the movement of carbon from plants to fungi was dramatically decreased. Our results suggest that while urban horticulture holds promise for sustainably enhancing local food production and addressing global food security, the unchecked presence of contaminants in these soils may pose a critical hurdle to realizing the potential of urban soils.

Prospects of phosphate solubilizing microorganisms in sustainable agriculture

Phosphorus (P), an essential macronutrient for various plant processes, is generally a limiting soil component for crop growth and yields. Organic and inorganic types of P are copious in soils, but their phyto-availability is limited as it is present largely in insoluble forms. Although phosphate fertilizers are applied in P-deficit soils, their undue use negatively impacts soil quality and the environment. Moreover, many P fertilizers are lost because of adsorption and fixation mechanisms, further reducing fertilizer efficiencies. The application of phosphate-solubilizing microorganisms (PSMs) is an environmentally friendly, low-budget, and biologically efficient method for sustainable agriculture without causing environmental hazards. These beneficial microorganisms are widely distributed in the rhizosphere and can hydrolyze inorganic and organic insoluble P substances to soluble P forms which are directly assimilated by plants. The present review summarizes and discusses our existing understanding related to various forms and sources of P in soils, the importance and P utilization by plants and microbes,, the diversification of PSMs along with mixed consortia of diverse PSMs including endophytic PSMs, the mechanism of P solubilization, and lastly constraints being faced in terms of production and adoption of PSMs on large scale have also been discussed.

Competitive relationships due to similar nutrient preferences reshape soil bacterial metacommunities

Paddy soil, as an ecosystem with alternating drained and flooded conditions, microorganisms in it can maintain the stability of the ecosystem by regulating the composition and diversity of its species when disturbed by external biotic or abiotic factors, and the regulatory mechanism in this process is a controversial topic in ecological research. In this study, we investigate the effects of pigeon feces addition on bacterial communities in three textured soils, two conditions (drained and flooded) based on microcosm experiment using high-throughput sequencing techniques. Our results show that pigeon feces addition reduced environmental heterogeneity and community diversity, both under flooded and drained conditions and in all textured soils, thereby decreasing the effectiveness of environmental selection and increasing diffusion limitations among bacterial communities. Bacterial communities are altered by environmental factors including total organic carbon, available nitrogen, total phosphorus, available phosphorus and available potassium, resulting in the formation of new community structures and dominant genera. Bacteria from pigeon feces did not colonize the original soil in large numbers, and the soil bacterial community structure changed, with some species replaced the indigenous ones as new dominant genera. As nutrient diffusion increases the nutrient content of the soil, this does not lead to species extinction; however, nutrient diffusion creates new nutrient preferences of the bacterial community, which causes direct competition between species, and contributes to the extinction and immigration species. Our results suggest that species replacement is an adaptive strategy of soil bacterial community in response to dispersal of pigeon feces, and that bacterial community regulate diversity and abundance of the community by enhancing species extinction and immigration, thereby preventing bacteria in pigeon feces from colonizing paddy soils and maintaining ecosystem stability.

Unraveling root and rhizosphere traits in temperate maize landraces and modern cultivars: Implications for soil resource acquisition and drought adaptation

A holistic understanding of plant strategies to acquire soil resources is pivotal in achieving sustainable food security. However, we lack knowledge about variety-specific root and rhizosphere traits for resource acquisition, their plasticity and adaptation to drought. We conducted a greenhouse experiment to phenotype root and rhizosphere traits (mean root diameter [Root D], specific root length [SRL], root tissue density, root nitrogen content, specific rhizosheath mass [SRM], arbuscular mycorrhizal fungi [AMF] colonization) of 16 landraces and 22 modern cultivars of temperate maize (Zea mays L.). Our results demonstrate that landraces and modern cultivars diverge in their root and rhizosphere traits. Although landraces follow a 'do-it-yourself' strategy with high SRLs, modern cultivars exhibit an 'outsourcing' strategy with increased mean Root Ds and a tendency towards increased root colonization by AMF. We further identified that SRM indicates an 'outsourcing' strategy. Additionally, landraces were more drought-responsive compared to modern cultivars based on multitrait response indices. We suggest that breeding leads to distinct resource acquisition strategies between temperate maize varieties. Future breeding efforts should increasingly target root and rhizosphere economics, with SRM serving as a valuable proxy for identifying varieties employing an outsourcing resource acquisition strategy.

Arbuscular mycorrhizal fungi attenuate negative impact of drought on soil functions

Although positive effects of arbuscular mycorrhizal (AM) fungi on plant performance under drought have been well documented, how AM fungi regulate soil functions and multifunctionality requires further investigation. In this study, we first performed a meta-analysis to test the potential role of AM fungi in maintaining soil functions under drought. Then, we conducted a greenhouse experiment, using a pair of hyphal ingrowth cores to spatially separate the growth of AM fungal hyphae and plant roots, to further investigate the effects of AM fungi on soil multifunctionality and its resistance against drought. Our meta-analysis showed that AM fungi promote multiple soil functions, including soil aggregation, microbial biomass and activities of soil enzymes related to nutrient cycling. The greenhouse experiment further demonstrated that AM fungi attenuate the negative impact of drought on these soil functions and thus multifunctionality, therefore, increasing their resistance against drought. Moreover, this buffering effect of AM fungi persists across different frequencies of water supply and plant species. These findings highlight the unique role of AM fungi in maintaining multiple soil functions by mitigating the negative impact of drought. Our study highlights the importance of AM fungi as a nature-based solution to sustaining multiple soil functions in a world where drought events are intensifying.

Absence of Gigasporales and rarity of spores in a hot desert revealed by a multimethod approach

Hot deserts impose extreme conditions on plants growing in arid soils. Deserts are expanding due to climate change, thereby increasing the vulnerability of ecosystems and the need to preserve them. Arbuscular mycorrhizal fungi (AMF) improve plant fitness by enhancing plant water/nutrient uptake and stress tolerance. However, few studies have focused on AMF diversity and community composition in deserts, and the soil and land use parameters affecting them. This study aimed to comprehensively describe AMF ecological features in a 5,000 km2 arid hyperalkaline region in AlUla, Saudi Arabia. We used a multimethod approach to analyse over 1,000 soil and 300 plant root samples of various species encompassing agricultural, old agricultural, urban and natural ecosystems. Our method involved metabarcoding using 18S and ITS2 markers, histological techniques for direct AMF colonization observation and soil spore extraction and observation. Our findings revealed a predominance of AMF taxa assigned to Glomeraceae, regardless of the local conditions, and an almost complete absence of Gigasporales taxa. Land use had little effect on the AMF richness, diversity and community composition, while soil texture, pH and substantial unexplained stochastic variance drove these compositions in AlUla soils. Mycorrhization was frequently observed in the studied plant species, even in usually non-mycorrhizal plant taxa (e.g. Amaranthaceae, Urticaceae). Date palms and Citrus trees, representing two major crops in the region, however, displayed a very low mycorrhizal frequency and intensity. AlUla soils had a very low concentration of spores, which were mostly small. This study generated new insight on AMF and specific behavioral features of these fungi in arid environments.

Impact of Plant-Microbe Interactions with a Focus on Poorly Investigated Urban Ecosystems-A Review

The urbanization process, which began with the Industrial Revolution, has undergone a considerable increase over the past few decades. Urbanization strongly affects ecological processes, often deleteriously, because it is associated with a decrease in green spaces (areas of land covered by vegetation), loss of natural habitats, increased rates of species extinction, a greater prevalence of invasive and exotic species, and anthropogenic pollutant accumulation. In urban environments, green spaces play a key role by providing many ecological benefits and contributing to human psychophysical well-being. It is known that interactions between plants and microorganisms that occur in the rhizosphere are of paramount importance for plant health, soil fertility, and the correct functioning of plant ecosystems. The growing diffusion of DNA sequencing technologies and "omics" analyses has provided increasing information about the composition, structure, and function of the rhizomicrobiota. However, despite the considerable amount of data on rhizosphere communities and their interactions with plants in natural/rural contexts, current knowledge on microbial communities associated with plant roots in urban soils is still very scarce. The present review discusses both plant-microbe dynamics and factors that drive the composition of the rhizomicrobiota in poorly investigated urban settings and the potential use of beneficial microbes as an innovative biological tool to face the challenges that anthropized environments and climate change impose. Unravelling urban biodiversity will contribute to green space management, preservation, and development and, ultimately, to public health and safety.

Bioprospecting for plant resilience to climate change: mycorrhizal symbionts of European and American beachgrass (Ammophila arenaria and Ammophila breviligulata) from maritime sand dunes

Climate change and global warming have contributed to increase terrestrial drought, causing negative impacts on agricultural production. Drought stress may be addressed using novel agronomic practices and beneficial soil microorganisms, such as arbuscular mycorrhizal fungi (AMF), able to enhance plant use efficiency of soil resources and water and increase plant antioxidant defence systems. Specific traits functional to plant resilience improvement in dry conditions could have developed in AMF growing in association with xerophytic plants in maritime sand dunes, a drought-stressed and low-fertility environment. The most studied of such plants are European beachgrass (Ammophila arenaria Link), native to Europe and the Mediterranean basin, and American beachgrass (Ammophila breviligulata Fern.), found in North America. Given the critical role of AMF for the survival of these beachgrasses, knowledge of the composition of AMF communities colonizing their roots and rhizospheres and their distribution worldwide is fundamental for the location and isolation of native AMF as potential candidates to be tested for promoting crop growth and resilience under climate change. This review provides quantitative and qualitative data on the occurrence of AMF communities of A. arenaria and A. breviligulata growing in European, Mediterranean basin and North American maritime sand dunes, as detected by morphological studies, trap culture isolation and molecular methods, and reports on their symbiotic performance. Moreover, the review indicates the dominant AMF species associated with the two Ammophila species and the common species to be further studied to assess possible specific traits increasing their host plants resilience toward drought stress under climate change.

Development of unique soil organic carbon stability index under influence of integrated nutrient management in four major soil orders of India

Stability of soil organic carbon (SOC) is pre-requisite for stabilization of C leading to long-term C sequestration. However, development of a comprehensive metric of SOC stability is a major challenge. The objectives for the study were to develop novel SOC stability indices by encompassing physical, chemical, and biochemical SOC stability parameters and identifying the most important indicators from a Mollisol, an Inceptisol, a Vertisol, and an Alfisol under long-term manuring and fertilization. The treatments were control, 100%NPK, 50% NPK+ 50% N through either farmyard manure, cereal residue, or green manure. SOC stability indicators were selected, transformed and integrated into unique SOC stability indices via conceptual framework and principal component analysis. Principal component analysis identified Al-macroaggregate, humic acid C-microaggregate, microaggregate-C, particulate organic matter-C-macroaggregate and polyphenol-microaggregate as the important SOC stability indicators. The principal component analysis -based SOC stability index varied from 0.2 to 0.9, 0.1 to 0.5, 0.2 to 0.6, 0.1 to 0.5 for Mollisol, Inceptisol, Vertisol and Alfisol, respectively. The SOC-stability index derived from conceptual framework and principal component analysis significantly lined up well with one another, although NaOCl-Res-C showed a high correlation with both conceptual framework (r = 0.8) and principal component analysis-based (r = 0.7) SOC stability indexes, suggesting that both methods might be used to quickly assess SOC stability in four soil orders. Overall, 50%NPK+50%N by farmyard manure or green manure emerged as the most effective management practices for enhancing stability of SOC in Mollisol, Inceptisol, Vertisol, and Alfisol of India which might act as major C sink in rice-wheat and maize-wheat cropping systems. The other aspect of C sequestration is to enhance agricultural productivity without depending much on expensive chemical fertilizers. The model yardstick thus developed for assessing SOC stability might be useful to other systems as well.

Mycorrhizal type and tree diversity affect foliar elemental pools and stoichiometry

Species-specific differences in nutrient acquisition strategies allow for complementary use of resources among plants in mixtures, which may be further shaped by mycorrhizal associations. However, empirical evidence of this potential role of mycorrhizae is scarce, particularly for tree communities. We investigated the impact of tree species richness and mycorrhizal types, arbuscular mycorrhizal fungi (AM) and ectomycorrhizal fungi (EM), on above- and belowground carbon (C), nitrogen (N), and phosphorus (P) dynamics. Soil and soil microbial biomass elemental dynamics showed weak responses to tree species richness and none to mycorrhizal type. However, foliar elemental concentrations, stoichiometry, and pools were significantly affected by both treatments. Tree species richness increased foliar C and P pools but not N pools. Additive partitioning analyses showed that net biodiversity effects of foliar C, N, P pools in EM tree communities were driven by selection effects, but in mixtures of both mycorrhizal types by complementarity effects. Furthermore, increased tree species richness reduced soil nitrate availability, over 2 yr. Our results indicate that positive effects of tree diversity on aboveground nutrient storage are mediated by complementary mycorrhizal strategies and highlight the importance of using mixtures composed of tree species with different types of mycorrhizae to achieve more multifunctional afforestation.

Enhancement of soil aggregation and physical properties through fungal amendments under varying moisture conditions

Soil structure and aggregation are crucial for soil functionality, particularly under drought conditions. Saprobic soil fungi, known for their resilience in low moisture conditions, are recognized for their influence on soil aggregate dynamics. In this study, we explored the potential of fungal amendments to enhance soil aggregation and hydrological properties across different moisture regimes. We used a selection of 29 fungal isolates, recovered from soils treated under drought conditions and varying in colony density and growth rate, for single-strain inoculation into sterilized soil microcosms under either low or high moisture (≤-0.96 and -0.03 MPa, respectively). After 8 weeks, we assessed soil aggregate formation and stability, along with soil properties such as soil water content, water hydrophobicity, sorptivity, total fungal biomass and water potential. Our findings indicate that fungal inoculation altered soil hydrological properties and improved soil aggregation, with effects varying based on the fungal strains and soil moisture levels. We found a positive correlation between fungal biomass and enhanced soil aggregate formation and stabilization, achieved by connecting soil particles via hyphae and modifying soil aggregate sorptivity. The improvement in soil water potential was observed only when the initial moisture level was not critical for fungal activity. Overall, our results highlight the potential of using fungal inoculation to improve the structure of agricultural soil under drought conditions, thereby introducing new possibilities for soil management in the context of climate change.

Arbuscular mycorrhiza convey significant plant carbon to a diverse hyphosphere microbial food web and mineral-associated organic matter

Arbuscular mycorrhizal fungi (AMF) transport substantial plant carbon (C) that serves as a substrate for soil organisms, a precursor of soil organic matter (SOM), and a driver of soil microbial dynamics. Using two-chamber microcosms where an air gap isolated AMF from roots, we 13CO2-labeled Avena barbata for 6 wk and measured the C Rhizophagus intraradices transferred to SOM and hyphosphere microorganisms. NanoSIMS imaging revealed hyphae and roots had similar 13C enrichment. SOM density fractionation, 13C NMR, and IRMS showed AMF transferred 0.77 mg C g-1 of soil (increasing total C by 2% relative to non-mycorrhizal controls); 33% was found in occluded or mineral-associated pools. In the AMF hyphosphere, there was no overall change in community diversity but 36 bacterial ASVs significantly changed in relative abundance. With stable isotope probing (SIP)-enabled shotgun sequencing, we found taxa from the Solibacterales, Sphingobacteriales, Myxococcales, and Nitrososphaerales (ammonium oxidizing archaea) were highly enriched in AMF-imported 13C (> 20 atom%). Mapping sequences from 13C-SIP metagenomes to total ASVs showed at least 92 bacteria and archaea were significantly 13C-enriched. Our results illustrate the quantitative and ecological impact of hyphal C transport on the formation of potentially protective SOM pools and microbial roles in the AMF hyphosphere soil food web.

Soil organic matter dynamics mediated by arbuscular mycorrhizal fungi - an updated conceptual framework

Arbuscular mycorrhizal (AM) fungi play an important role in soil organic matter (SOM) formation and stabilization. Previous studies have emphasized organic compounds produced by AM fungi as persistent binding agents for aggregate formation and SOM storage. This concept overlooks the multiple biogeochemical processes mediated by AM fungal activities, which drive SOM generation, reprocessing, reorganization, and stabilization. Here, we propose an updated conceptual framework to facilitate a mechanistic understanding of the role of AM fungi in SOM dynamics. In this framework, four pathways for AM fungi-mediated SOM dynamics are included: 'Generating', AM fungal exudates and biomass serve as key sources of SOM chemodiversity; 'Reprocessing', hyphosphere microorganisms drive SOM decomposition and resynthesis; 'Reorganizing', AM fungi mediate soil physical changes and influence SOM transport, redistribution, transformation, and storage; and 'Stabilizing', AM fungi drive mineral weathering and organo-mineral interactions for SOM stabilization. Moreover, we discuss the AM fungal role in SOM dynamics at different scales, especially when translating results from small scales to complex larger scales. We believe that working with this conceptual framework can allow a better understanding of AM fungal role in SOM dynamics, therefore facilitating the development of mycorrhiza-based technologies toward soil health and global change mitigation.

Mycorrhizal effects on crop yield and soil ecosystem functions in a long-term tillage and fertilization experiment

It is well understood that agricultural management influences arbuscular mycorrhizal (AM) fungi, but there is controversy about whether farmers should manage for AM symbiosis. We assessed AM fungal communities colonizing wheat roots for three consecutive years in a long-term (> 14 yr) tillage and fertilization experiment. Relationships among mycorrhizas, crop performance, and soil ecosystem functions were quantified. Tillage, fertilizers and continuous monoculture all reduced AM fungal richness and shifted community composition toward dominance of a few ruderal taxa. Rhizophagus and Dominikia were depressed by tillage and/or fertilization, and their abundances as well as AM fungal richness correlated positively with soil aggregate stability and nutrient cycling functions across all or no-tilled samples. In the field, wheat yield was unrelated to AM fungal abundance and correlated negatively with AM fungal richness. In a complementary glasshouse study, wheat biomass was enhanced by soil inoculum from unfertilized, no-till plots while neutral to depressed growth was observed in wheat inoculated with soils from fertilized and conventionally tilled plots. This study demonstrates contrasting impacts of low-input and conventional agricultural practices on AM symbiosis and highlights the importance of considering both crop yield and soil ecosystem functions when managing mycorrhizas for more sustainable agroecosystems.

Contribution of Particulates to Airborne Disease Transmission and Severity: A Review

The emergence of coronavirus disease 2019 (COVID-19) has catalyzed great interest in the spread of airborne pathogens. Airborne infectious diseases are classified into viral, bacterial, and fungal infections. Environmental factors can elevate their transmission and lethality. Air pollution has been reported as the leading environmental cause of disease and premature death worldwide. Notably, ambient particulates of various components and sizes are harmful pollutants. There are two prominent health effects of particles in the atmosphere: (1) particulate matter (PM) penetrates the respiratory tract and adversely affects health, such as heart and respiratory diseases; and (2) bioaerosols of particles act as a medium for the spread of pathogens in the air. Particulates contribute to the occurrence of infectious diseases by increasing vulnerability to infection through inhalation and spreading disease through interactions with airborne pathogens. Here, we focus on the synergistic effects of airborne particulates on infectious disease. We outline the concepts and characteristics of bioaerosols, from their generation to transformation and circulation on Earth. Considering that microorganisms coexist with other particulates as bioaerosols, we investigate studies examining respiratory infections associated with airborne PM. Furthermore, we discuss four factors (meteorological, biological, physical, and chemical) that may impact the influence of PM on the survival of contagious pathogens in the atmosphere. Our review highlights the significant role of particulates in supporting the transmission of infectious aerosols and emphasizes the need for further research in this area.

Plant-microbe interactions through a lens: tales from the mycorrhizosphere

BACKGROUND

The soil microbiome plays a pivotal role in maintaining ecological balance, supporting food production, preserving water quality and safeguarding human health. Understanding the intricate dynamics within the soil microbiome necessitates unravelling complex bacterial-fungal interactions (BFIs). BFIs occur in diverse habitats, such as the phyllosphere, rhizosphere and bulk soil, where they exert substantial influence on plant-microbe associations, nutrient cycling and overall ecosystem functions. In various symbiotic associations, fungi form mycorrhizal connections with plant roots, enhancing nutrient uptake through the root and mycorrhizal pathways. Concurrently, specific soil bacteria, including mycorrhiza helper bacteria, play a pivotal role in nutrient acquisition and promoting plant growth. Chemical communication and biofilm formation further shape plant-microbial interactions, affecting plant growth, disease resistance and nutrient acquisition processes.

SCOPE

Promoting synergistic interactions between mycorrhizal fungi and soil microbes holds immense potential for advancing ecological knowledge and conservation. However, despite the significant progress, gaps remain in our understanding of the evolutionary significance, perception, functional traits and ecological relevance of BFIs. Here we review recent findings obtained with respect to complex microbial communities - particularly in the mycorrhizosphere - and include the latest advances in the field, outlining their profound impacts on our understanding of ecosystem dynamics and plant physiology and function.

CONCLUSIONS

Deepening our understanding of plant BFIs can help assess their capabilities with regard to ecological and agricultural safe-guarding, in particular buffering soil stresses, and ensuring sustainable land management practices. Preserving and enhancing soil biodiversity emerge as critical imperatives in sustaining life on Earth amidst pressures of anthropogenic climate change. A holistic approach integrates scientific knowledge on bacteria and fungi, which includes their potential to foster resilient soil ecosystems for present and future generations.

The interplay between microbial communities and soil properties

In recent years, there has been considerable progress in determining the soil properties that influence the structure of the soil microbiome. By contrast, the effects of microorganisms on their soil habitat have received less attention with most previous studies focusing on microbial contributions to soil carbon and nitrogen dynamics. However, soil microorganisms are not only involved in nutrient cycling and organic matter transformations but also alter the soil habitat through various biochemical and biophysical mechanisms. Such microbially mediated modifications of soil properties can have local impacts on microbiome assembly with pronounced ecological ramifications. In this Review, we describe the processes by which microorganisms modify the soil environment, considering soil physics, hydrology and chemistry. We explore how microorganism-soil interactions can generate feedback loops and discuss how microbially mediated modifications of soil properties can serve as an alternative avenue for the management and manipulation of microbiomes to combat soil threats and global change.

Manipulation of soil mycorrhizal fungi influences floral traits

Most plants form root hyphal relationships with mycorrhizal fungi, especially arbuscular mycorrhizal fungi (AMF). These associations are known to positively impact plant biomass and competitive ability. However, less is known about how mycorrhizas impact other ecological interactions, such as those mediated by pollinators. We performed a meta-regression of studies that manipulated AMF and measured traits related to pollination, including floral display size, rewards, visitation, and reproduction, extracting 63 studies with 423 effects. On average, the presence of mycorrhizas was associated with positive effects on floral traits. Specifically, we found impacts of AMF on floral display size, pollinator visitation and reproduction, and a positive but nonsignificant impact on rewards. Studies manipulating mycorrhizas with fungicide tended to report contrasting results, possibly because fungicide destroys both beneficial and pathogenic microbes. Our study highlights the potential for relationships with mycorrhizal fungi to play an important, yet underrecognized role in plant-pollinator interactions. With heightened awareness of the need for a more sustainable agricultural industry, mycorrhizal fungi may offer the opportunity to reduce reliance on inorganic fertilizers. At the same time, fungicides are now ubiquitous in agricultural systems. Our study demonstrates indirect ways in which plant-belowground fungal partnerships could manifest in plant-pollinator interactions.

Drought legacy interacts with wildfire to alter soil microbial communities in a Mediterranean climate-type forest

Mediterranean forest ecosystems will be increasingly affected by hotter drought and more frequent and severe wildfire events in the future. However, little is known about the longer-term responses of these forests to multiple disturbances and the forests' capacity to maintain ecosystem function. This is particularly so for below-ground organisms, which have received less attention than those above-ground, despite their essential contributions to forest function. We investigated rhizosphere microbial communities in a resprouting Eucalyptus marginata forest, southwestern Australia, that had experienced a severe wildfire four years previously, and a hotter drought eight years previously. Our aim was to understand how microbial communities are affected over longer-term trajectories by hotter drought and wildfire, singularly, and in combination. Fungal and bacterial DNA was extracted from soil samples, amplified, and subjected to high throughput sequencing. Richness, diversity, composition, and putative functional groups were then examined. We found a monotonic decrease in fungal, but not bacterial, richness and diversity with increasing disturbance with the greatest changes resulting from the combination of drought and wildfire. Overall fungal and bacterial community composition reflected a stronger effect of fire than drought, but the combination of both produced the greatest number of indicator taxa for fungi, and a significant negative effect on the abundance of several fungal functional groups. Key mycorrhizal fungi, fungal saprotrophs and fungal pathogens were found at lower proportions in sites affected by drought plus wildfire. Wildfire had a positive effect on bacterial hydrogen and bacterial nitrogen recyclers. Fungal community composition was positively correlated with live tree height. These results suggest that microbial communities, in particular key fungal functional groups, are highly responsive to wildfire following drought. Thus, a legacy of past climate conditions such as hotter drought can be important for mediating the responses of soil microbial communities to subsequent disturbance like wildfire.

Composite biomediated engineering approaches for improving problematic soils: Potentials and opportunities

Several conventional chemical stabilizers are used for soil stabilization, among which cement is widely adopted. However, the high energy consumption and environmental challenges associated with these stabilizers have necessitated the transition toward the adoption/deployment of eco-friendly approaches for soil stabilization. Biomediated techniques are sustainable soil improvement methods adopting less toxic microorganisms, enzymes, or polymers for cementing soil. However, these processes also have several drawbacks, such as slow hardening, environmental impact, high cost, and lack of compatibility with different types of soils. It is hypothesized that these limitations may be overcome by exploring the prospects and opportunities offered by hybrid technological approaches involving the integration of nontraditional stabilizers and microbial-induced biomineralization processes for improving problematic soils. This paper discusses selected previous studies integrating different technologies and their benefits and challenges. The emerging fungi-based bio-mediation techniques and the possibility of forming sustainable fungal-based biocomposites to improve problematic soils are also highlighted.

Long-term tropospheric ozone pollution disrupts plant-microbe-soil interactions in the agroecosystem

Tropospheric ozone (O3 ) threatens agroecosystems, yet its long-term effects on intricate plant-microbe-soil interactions remain overlooked. This study employed two soybean genotypes of contrasting O3 -sensitivity grown in field plots exposed elevated O3 (eO3 ) and evaluated cause-effect relationships with their associated soil microbiomes and soil quality. Results revealed long-term eO3 effects on belowground soil microbiomes and soil health surpass damage visible on plants. Elevated O3 significantly disrupted belowground bacteria-fungi interactions, reduced fungal diversity, and altered fungal community assembly by impacting soybean physiological properties. Particularly, eO3 impacts on plant performance were significantly associated with arbuscular mycorrhizal fungi, undermining their contribution to plants, whereas eO3 increased fungal saprotroph proliferation, accelerating soil organic matter decomposition and soil carbon pool depletion. Free-living diazotrophs exhibited remarkable acclimation under eO3 , improving plant performance by enhancing nitrogen fixation. However, overarching detrimental consequences of eO3 negated this benefit. Overall, this study demonstrated long-term eO3 profoundly governed negative impacts on plant-soil-microbiota interactions, pointing to a potential crisis for agroecosystems. These findings highlight urgent needs to develop adaptive strategies to navigate future eO3 scenarios.

Ability of seedlings to survive heat and drought portends future demographic challenges for five southwestern US conifers

Climate change and disturbance are altering forests and the rates and locations of tree regeneration. In semi-arid forests of the southwestern USA, limitations imposed by hot and dry conditions are likely to influence seedling survival. We examined how the survival of 1-year seedlings of five southwestern US conifer species whose southwestern distributions range from warmer and drier woodlands and forests (Pinus edulis Engelm., Pinus ponderosa Douglas ex C. Lawson) to cooler and wetter subalpine forests (Pseudotsuga menziesii (Mirb.) Franco, Abies concolor (Gord. & Glend.) Lindl. Ex Hildebr. and Picea engelmannii Parry ex Engelm.) changed in response to low moisture availability, high temperatures and high vapor pressure deficit in incubators. We used a Bayesian framework to construct discrete-time proportional hazard models that explained 55-75% of the species-specific survival variability. We applied these to the recent climate (1980-2019) of the southwestern USA as well as 1980-2099 CMIP5 climate projections with the RCP8.5 emissions pathway. We found that the more mesic species (i.e., P. menziesii, A. concolor and P. engelmannii) were more susceptible to the effects of hot and dry periods. However, their existing ranges are not projected to experience the conditions we tested as early in the 21st century as the more xeric P. edulis and P. ponderosa, leading to lower percentages of their existing ranges predicted to experience seedling-killing conditions. By late-century, extensive areas of each species southwestern range could experience climate conditions that increase the likelihood of seedling mortality. These results demonstrate that empirically derived physiological limitations can be used to inform where species composition or vegetation type change are likely to occur in the southwestern USA.

Synergistic effects of arbuscular mycorrhizal fungi and biochar are highly beneficial to Ligustrum lucidum seedlings in Cd-contaminated soil

Cadmium (Cd) contamination is a widespread environmental issue. There is a lack of knowledge about the impacts of applying arbuscular mycorrhizal fungi (AMF) and biochar, either alone or in their combination, on alleviating Cd phytotoxicity in Ligustrum lucidum. Therefore, a pot experiment was conducted in a greenhouse, where L. lucidum seedlings were randomly subjected to four regimes of AMF treatments (inoculation with sterilized AMF, with Rhizophagus irregularis, Diversispora versiformis, alone or a mixture of these two fungi), and two regimes of biochar treatments (with or without rice-husk biochar), as well as three regimes of Cd treatments (0, 15, and 150 mg kg-1), to examine the responses of growth, photosynthetic capabilities, soil enzymatic activities, nutritional concentrations, and Cd absorption of L. lucidum plants to the interactive effects of AMF, biochar, and Cd. The results demonstrated that under Cd contaminations, AMF alone significantly increased plant total dry weight, soil pH, and plant nitrogen (N) concentration by 84%, 3.2%, and 13.2%, respectively, and inhibited soil Cd transferring to plant shoot by 42.2%; biochar alone significantly enhanced net photosynthetic rate, soil pH, and soil catalase of non-mycorrhizal plants by 16.4%, 9%, and 11.9%, respectively, and reduced the soil Cd transferring to plant shoot by 44.7%; the additive effect between AMF and biochar greatly enhanced plant total dry weight by 101.9%, and reduced the soil Cd transferring to plant shoot by 51.6%. Furthermore, dual inoculation with D. versiformis and R. irregularis conferred more benefits on plants than the single fungal species did. Accordingly, amending Cd-contaminated soil with the combination of mixed-fungi inoculation and biochar application performed the best than either AMF or biochar alone. These responses may have been attributed to higher mycorrhizal colonization, soil pH, biomass accumulation, and biomass allocation to the roots, as well as photosynthetic capabilities. In conclusion, the combined use of mixed-fungi involving D. versiformis and R. irregularis and biochar addition had significant synergistic effects on enhancing plant performance and reducing Cd uptake of L. lucidum plants in Cd-contaminated soil.

Microplastic fibres affect soil fungal communities depending on drought conditions with consequences for ecosystem functions

Microplastics affect soil functions depending on drought conditions. However, how their combined effect influences soil fungi and their linkages with ecosystem functions is still unknown. To address this, we used rhizosphere soil from a previous experiment in which we employed microplastic fibres addition and drought in a factorial design, and evaluated their effects on soil fungal communities. Microplastics decreased soil fungal richness under well-watered conditions, likely linked to microplastics leaching toxic substances into the soil, and microplastic effects on root fineness. Under drought, by contrast, microplastics increased pathogen and total fungal richness, likely related to microplastic positive effects on soil properties, such as water holding capacity, porosity or aggregation. Soil fungal richness was the attribute most affected by microplastics and drought. Microplastics altered the relationships between soil fungi and ecosystem functions to the point that many of them flipped from positive to negative or disappeared. The combined effect of microplastics and drought on fungal richness mitigated their individual negative effect (antagonism), suggesting that changes in soil water conditions may alter the action mode of microplastics in soil. Microplastic leaching of harmful substances can be mitigated under drought, while the improvement of soil properties by microplastics may alleviate such drought conditions.

Microbial Necromass, Lignin, and Glycoproteins for Determining and Optimizing Blue Carbon Formation

Coastal wetlands contribute to the mitigation of climate change through the sequestration of "blue carbon". Microbial necromass, lignin, and glycoproteins (i.e., glomalin-related soil proteins (GRSP)), as important components of soil organic carbon (SOC), are sensitive to environmental change. However, their contributions to blue carbon formation and the underlying factors remain largely unresolved. To address this paucity of knowledge, we investigated their contributions to blue carbon formation along a salinity gradient in coastal marshes. Our results revealed decreasing contributions of microbial necromass and lignin to blue carbon as the salinity increased, while GRSP showed an opposite trend. Using random forest models, we showed that their contributions to SOC were dependent on microbial biomass and resource stoichiometry. In N-limited saline soils, contributions of microbial necromass to SOC decreased due to increased N-acquisition enzyme activity. Decreases in lignin contributions were linked to reduced mineral protection offered by short-range-ordered Fe (FeSRO). Partial least-squares path modeling (PLS-PM) further indicated that GRSP could increase microbial necromass and lignin formation by enhancing mineral protection. Our findings have implications for improving the accumulation of refractory and mineral-bound organic matter in coastal wetlands, considering the current scenario of heightened nutrient discharge and sea-level rise.

Arbuscular Mycorrhizal Fungi Drive Organo-Mineral Association in Iron Ore Tailings: Unravelling Microstructure at the Submicron Scale by Synchrotron-Based FTIR and STXM-NEXAFS

Arbuscular mycorrhizal (AM) fungi play an important role in organic matter (OM) stabilization in Fe ore tailings for eco-engineered soil formation. However, little has been understood about the AM fungi-derived organic signature and organo-mineral interactions in situ at the submicron scale. In this study, a compartmentalized cultivation system was used to investigate the role of AM fungi in OM formation and stabilization in tailings. Particularly, microspectroscopic analyses including synchrotron-based transmission Fourier transform infrared (FTIR) and scanning transmission X-ray microspectroscopy combined with near-edge X-ray absorption fine structure spectroscopy (STXM-NEXAFS) were employed to characterize the chemical signatures at the AM fungal-mineral and mineral-OM interfaces at the submicron scale. The results indicated that AM fungal mycelia developed well in the tailings and entangled mineral particles for aggregation. AM fungal colonization enhanced N-rich OM stabilization through organo-mineral association. Bulk spectroscopic analysis together with FTIR mapping revealed that fungi-derived lipids, proteins, and carbohydrates were associated with Fe/Si minerals. Furthermore, STXM-NEXAFS analysis revealed that AM fungi-derived aromatic, aliphatic, and carboxylic/amide compounds were heterogeneously distributed and trapped by Fe(II)/Fe(III)-bearing minerals originating from biotite-like minerals weathering. These findings imply that AM fungi can stimulate mineral weathering and provide organic substances to associate with minerals, contributing to OM stabilization and aggregate formation as key processes for eco-engineered soil formation in tailings.

The role of arbuscular mycorrhizal fungi in the alleviation of cadmium stress in cereals: A multilevel meta-analysis

The symbiotic relationships between crop species and arbuscular mycorrhizal fungi (AMF) are crucial for plant health, productivity, and environmental sustainability. The roles of AMF in reducing crop stress caused by cadmium (Cd) toxicity and in the remediation of Cd-contaminated soil are not fully understood. Here we report on a meta-analysis that sought to identify the functions of AMF in cereals under Cd stress. A total of 54 articles published between January 1992 and September 2022 were used to create the dataset, which provided 7216 data sets on mycorrhizal cereals under Cd stress examined. AMF effects on colonization rate, biomass, physiological level, nutritional level, and plant Cd level were measured using the logarithmic response ratio (Ln R). The results showed that AMF overall greatly reduced 5.14 - 33.6 % Cd stress on cereals in greenhouse experiments under controlled conditions. AMF colonization significantly stimulated crop biomass by 65.7 %, boosted the formation of photosynthetic pigments (23.2 %), and greatly increased plant nitrogen (24.8 %) and phosphorus (58.4 %) uptake. The dilution effect of mycorrhizal plants made the Cd concentration decline by 25.2 % in AMF plants compared to non-mycorrhizal ones. AMF also alleviated Cd stress by improving osmotic regulators (soluble protein, sugar, and total proline, from 14.8 to 36.0 %) and lowering the membrane lipid peroxidation product (MDA, 12.9 %). Importantly, the results from the random forest and model selection analysis demonstrated that crop type, soil characteristics, chemical form, and Cd levels were the main factors determining the function of AMF in alleviating Cd stress. Additionally, there was a significant interaction between AMF colonization rate and Cd addition, but their interactive effect was less than the colonization rate alone. This meta-analysis demonstrated that AMF inoculation could be considered as a promising strategy for mitigation of Cd stress in cereals.

Environmental modulation of plant mycorrhizal traits in the global flora

Mycorrhizal symbioses are known to strongly influence plant performance, structure plant communities and shape ecosystem dynamics. Plant mycorrhizal traits, such as those characterising mycorrhizal type (arbuscular (AM), ecto-, ericoid or orchid mycorrhiza) and status (obligately (OM), facultatively (FM) or non-mycorrhizal) offer valuable insight into plant belowground functionality. Here, we compile available plant mycorrhizal trait information and global occurrence data (∼ 100 million records) for 11,770 vascular plant species. Using a plant phylogenetic mega-tree and high-resolution climatic and edaphic data layers, we assess phylogenetic and environmental correlates of plant mycorrhizal traits. We find that plant mycorrhizal type is more phylogenetically conserved than plant mycorrhizal status, while environmental variables (both climatic and edaphic; notably soil texture) explain more variation in mycorrhizal status, especially FM. The previously underestimated role of environmental conditions has far-reaching implications for our understanding of ecosystem functioning under changing climatic and soil conditions.