Arbuscular Mycorrhizal Fungal Taxa Research Articles

Extreme environments simplify reassembly of communities of arbuscular mycorrhizal fungi.

The ecological impacts of long-term (press) disturbance on mechanisms regulating the relative abundance (i.e., commonness or rarity) and temporal dynamics of species within a community remain largely unknown. This is particularly true for the functionally important arbuscular mycorrhizal (AM) fungi; obligate plant-root endosymbionts that colonize more than two-thirds of terrestrial plant species. Here, we use high-resolution amplicon sequencing to examine how AM fungal communities in a specific extreme ecosystem-mofettes or natural CO2 springs caused by geological CO2 exhalations-are affected by long-term stress. We found that in mofettes, specific and temporally stable communities form as a subset of the local metacommunity. These communities are less diverse and dominated by adapted, "stress tolerant" taxa. Those taxa are rare in control locations and more benign environments worldwide, but show a stable temporal pattern in the extreme sites, consistently dominating the communities in grassland mofettes. This pattern of lower diversity and high dominance of specific taxa has been confirmed as relatively stable over several sampling years and is independently observed across multiple geographic locations (mofettes in different countries). This study implies that the response of soil microbial community composition to long-term stress is relatively predictable, which can also reflect the community response to other anthropogenic stressors (e.g., heavy metal pollution or land use change). Moreover, as AM fungi are functionally differentiated, with different taxa providing different benefits to host plants, changes in community structure in response to long-term environmental change have the potential to impact terrestrial plant communities and their productivity.IMPORTANCEArbuscular mycorrhizal (AM) fungi form symbiotic relationships with more than two-thirds of plant species. In return for using plant carbon as their sole energy source, AM fungi improve plant mineral supply, water balance, and protection against pathogens. This work demonstrates the importance of long-term experiments to understand the effects of long-term environmental change and long-term disturbance on terrestrial ecosystems. We demonstrated a consistent response of the AM fungal community to a long-term stress, with lower diversity and a less variable AM fungal community over time under stress conditions compared to the surrounding controls. We have also identified, for the first time, a suite of AM fungal taxa that are consistently observed across broad geographic scales in stressed and anthropogenically heavily influenced ecosystems. This is critical because global environmental change in terrestrial ecosystems requires an integrative approach that considers both above- and below-ground changes and examines patterns over a longer geographic and temporal scale, rather than just single sampling events.

Tracking arbuscular mycorrhizal fungi to their source: active inoculation and passive dispersal differentially affect community assembly in urban soils.

Communities of arbuscular mycorrhizal (AM) fungi assemble passively over time via biotic and abiotic mechanisms. In degraded soils, AM fungal communities can assemble actively when humans manage mycorrhizas for ecosystem restoration. We investigated mechanisms of urban AM fungal community assembly in a 2-yr green roof experiment. We compared AM fungal communities in inoculated and uninoculated trays to samples from two potential sources: the inoculum and air. Active inoculation stimulated more distinct and diverse AM fungal communities, an effect that intensified over time. In the treatment trays, 45% of AM fungal taxa were detected in the inoculum, 2% were detected in aerial samples, 23% were detected in both inoculum and air, and 30% were not detected in either source. Passive dispersal of AM fungi likely resulted in the successful establishment of a small number of species, but active inoculation with native AM fungal species resulted in an immediate shift to a diverse and unique fungal community. When urban soils are constructed or modified by human activity, this is an opportunity for intervention with AM fungi that will persist and add diversity to that system.

Divergent responses between lineages of arbuscular mycorrhizal fungi to soil phosphorus and nitrogen availability

Arbuscular mycorrhizal (AM) associations are multifunctional. Two important functions they perform are facilitating nutrient uptake in host plants and protecting plants from biotic stress, among other functions. AM fungal taxa vary in how capably they perform these functions and can also respond differently to environmental selection. Therefore, there is a need to better understand how particular environmental variables might alter the response of AM fungal communities. Here, we analysed data from a DNA-based survey of fungal communities in soils collected throughout Australia to observe relationships among soil nitrogen and phosphorus availability and the abundance of two AM fungal taxa that reportedly vary in function – the Gigasporaceae (putatively more important for nutrient uptake) and Glomeraceae (putatively more important for biotic stress). Relationships were assessed in three vegetation types – grasslands, forests and woodlands – to assess whether associations with soil nutrition varied depending on carbon availability for AM fungi. Fungi from the Gigasporaceae decreased in frequency as available phosphorus increased, while those from the Glomeraceae increased or were unresponsive as available phosphorus increased. Similar patterns were observed for nitrate availability, although only in woodlands. These patterns are consistent with expectations that AM fungi from the Gigasporaceae, in general, are better suited to alleviate nutrient limitation in hosts as soil chemical fertility decreases. This knowledge may aid in implementing optimal strategies involving AM fungal inoculum best suited to the local conditions of future land management and agricultural projects.

Impacts of Lithology and Slope Position on Arbuscular Mycorrhizal Fungi Communities in a Karst Forest Soil.

The influence of lithology and slope position on arbuscular mycorrhizal fungi (AMF) communities has been explored in various ecosystems, but there is a limited understanding of these mechanisms in karst regions. This study focused on typical karst hills with contrasting lithologies, specifically dolomite and limestone. Additionally, three slope positions (upper, middle, and lower) were investigated within each hill in karst forest ecosystems. Total phosphorus (TP) content in the soil was higher in dolomite compared to limestone. Conversely, exchangeable calcium (Ca) was lower in dolomite than in limestone. Notably, the lithology, rather than the slope position, exerted a significant impact on AMF diversity and abundance and the presence of specific AMF taxa. Dolomite exhibited greater AMF richness and a higher Shannon index in comparison to limestone when not accounting for slope position. The AMF community composition differed between dolomite and limestone. For instance, without considering slope position, the relative abundance of Acaulospora, Diversispora, and Paraglomus was higher in dolomite than in limestone, while the relative abundance of Claroideoglomus displayed an opposing trend. Furthermore, a more complex interaction among AMF taxa was observed in dolomite as compared to limestone, as evidenced by an increase in the number of nodes and edges in the co-occurrence networks within the dolomite. The genera Glomus, Claroideoglomus, and Diversispora exhibited a higher number of links with each other and with other AMF taxa. The study identified TP and Ca as the primary factors determining variations in AMF diversity between dolomite and limestone. Consequently, it is imperative to consider the underlying lithology and soil conditions when addressing the restoration of degraded karst hilly areas.

Arbuscular mycorrhizal fungi with contrasting life-history strategies differently affect health-promoting compounds in field-grown tomato by changing arbuscule occurrence and mycorrhizal assemblages in roots

Contrasting life-history characteristics of arbuscular mycorrhizal (AM) fungal families may have important implications for mycorrhizal functioning. Nevertheless, the effect of inoculation with AM fungi having different life-history strategies on the quality parameters of tomato fruits was not investigated. In this study, fruit and sauce quality of two tomato varieties were evaluated in field conditions after inoculation with four AM fungal species belonging to Glomeraceae and Gigasporaceae. The functional relationship between AM fungal traits (i.e., root colonization structures, community diversity) and fruit quality parameters was analyzed. AM fungal inoculation increased total phenols (TPC) and lycopene concentration in fruits of both varieties (47% and 247%, respectively) and antioxidant activity in var. Rio Grande (85%). Gigasporaceae were more effective in increasing TPC and antioxidant activity compared to Glomeraceae in var. Rio Grande. Gigaspora gigantea outperformed Scutellospora pellucida in var. Pisanello for TPC, antioxidant activity, and lycopene. Inoculated strains of G. gigantea, S. pellucida, Funneliformis mosseae, and Sclerocystis sinuosa were molecularly retrieved within tomato roots. In both varieties, a functional relationship between occurrence of arbuscules in roots and fruit quality was found. In var. Rio Grande, the abundance of some native AM fungal taxa shaped the pattern of fruit quality parameters. Gigasporaceae might be of great relevance for the synthesis of health-promoting compounds in tomato and should be included in biostimulant programmes targeting the production of high-quality vegetables.

Arbuscular mycorrhizae mitigate negative impacts of soil biodiversity loss on grassland productivity

Grassland degradation decreases ecosystem productivity and diminishes soil biodiversity, leading to the loss of beneficial microorganisms. Arbuscular mycorrhizal fungi (AMF) play a critical role in ecosystem functioning, being a key link between plant and microbial communities, soil, and vegetation. Here, we evaluated the potential of increasing the productivity of degraded grassland by AMF inoculation.A gradient of soil biodiversity: complete sterilization, low, moderate, and high biodiversity was established using the dilution-to-extinction approach. Grassland microcosms under greenhouse conditions were inoculated with three AMF taxa in an increasing diversity: no AMF, single AMF taxa, and all three AMF taxa together.The loss of soil biodiversity decreased plant community productivity, primarily due to reduced biomass of legumes and non-N2-fixing forbs. AMF inoculation raised plant community productivity by 190%, mainly attributed to the greater biomass of legumes and non-N2-fixing forbs. This positive effect of AMF inoculation was particularly pronounced on soils with low biodiversity, where soil mutualists were absent. The biomass of grasses remained independent of AMF inoculation. This differential responsiveness to mycorrhiza was mainly due to the distinctive plant traits of each plant functional group. Inoculating with a single AMF was more beneficial for plant biomass production than inoculation with multiple AMF under lower levels of soil biodiversity, probably due to high functional redundancy among AMF taxa.In conclusion, AMF inoculation reduced the adverse impact of soil degradation and biodiversity loss on plant biomass and vegetation development, highlighting the key roles and importance of AMF for grassland restoration.

GlobalAMFungi: a global database of arbuscular mycorrhizal fungal occurrences from high-throughput sequencing metabarcoding studies.

Arbuscular mycorrhizal (AM) fungi are crucial mutualistic symbionts of the majority of plant species, with essential roles in plant nutrient uptake and stress mitigation. The importance of AM fungi in ecosystems contrasts with our limited understanding of the patterns of AM fungal biogeography and the environmental factors that drive those patterns. This article presents a release of a newly developed global AM fungal dataset (GlobalAMFungi database, https://globalamfungi.com) that aims to reduce this knowledge gap. It contains almost 50 million observations of Glomeromycotinian AM fungal amplicon DNA sequences across almost 8500 samples with geographical locations and additional metadata obtained from 100 original studies. The GlobalAMFungi database is built on sequencing data originating from AM fungal taxon barcoding regions in: i) the small subunit rRNA (SSU) gene; ii) the internal transcribed spacer 2 (ITS2) region; and iii) the large subunit rRNA (LSU) gene. The GlobalAMFungi database is an open source and open access initiative that compiles the most comprehensive atlas of AM fungal distribution. It is designed as a permanent effort that will be continuously updated by its creators and through the collaboration of the scientific community. This study also documented applicability of the dataset to better understand ecology of AM fungal taxa.

Habitat heterogeneity drives arbuscular mycorrhizal fungi and shrub communities in karst ecosystems

Arbuscular mycorrhizal fungi (AMF) constitute one of the factors that regulate the success of vegetation restoration. Karst ecosystems are heterogenous in nutrient content and plant communities because of preferential water fluxes within cracks and gullies in the soil parent material. The effects of habitat on soil nutrients, shrub, and AMF diversity in karst ecosystems are yet to be established. Thus, we investigated the diversity of shrubs and AMF within three habitats: i) rocky soil surface (Rock), ii) soil surface (Soil), and iii) rocky gully (Gully) in a typical karst shrub ecosystem. We observed that AMF diversity was independent of the sampling location, whereas AMF abundance and the shrub Shannon index increased with sampling distance, reaching a plateau in a sampling area of 1000 m2. The AMF community composition was driven by dominating shrubs (Vitex negundo, Tirpitzia ovoidea). Higher shrub diversity and AMF abundance occurred in Rock than in Soil and Gully areas, suggesting higher habitat heterogeneity in Rock areas. Based on co-occurrence network analysis, interactions with a high link number among the AMF taxa were stronger in Rock than in Gully because the network complexity in the Rock areas strongly depended on symbiosis with AMF taxa to cope with high habitat heterogeneity. The Random forest model revealed that AMF abundance was mainly affected by available phosphorous, total potassium, and shrub diversity. Available phosphorous, soil pH, and exchangeable Ca2+, rather than plant diversity, were the main factor controlling AMF community composition. Overall, the results suggest that the increase in shrub diversity raised AMF abundance and richness, and strengthened the interactions among AMF taxa because of nutrient exchange. Thus, increasing habitat heterogeneity with abundant shrub diversity, but soil nutrient limitation, enriches AMF abundance and diversity.

Morphological and Molecular Characterizations of Arbuscular Mycorrhizal Fungi and Their Influence on Soil Physicochemical Properties and Plant Nutrition.

Pulses are considered a remarkable and stable source of nutrients, which are being presently extensively cultivated and consumed in different parts of the world. Pulses belong to the family Leguminosae and are a rich source of nutrients such as phosphorus (P) and nitrogen (N) for best growth via symbiotic relationship with bacteria and AMF (arbuscular mycorrhizal fungi). The aim of the current study was evaluating the influence of AMF diversity associated with various pulses (French bean, mung bean, kidney bean, peas, soybean, peanuts, and grams). Furthermore, AMF characterization was done using morphological features of spores and sequencing of the rDNA gene, which confirmed the existence of 10 different AMF taxa. Among the different genera, the genus Glomus was observed to be the most dominant with 30% species followed by Gigaspora (22%), Sclerocystis (12%), Acaulospora (8%), Rhizophagus and Septoglomus (7%), Diversispora (5%), and Claroideoglomus, Archaeospora, and Ambispora (3%). Furthermore, soil physicochemical analysis and percentage of AMF colonization results revealed the fact that the phosphorus content (inversely proportional to the AMF diversity) was a determining factor of AMF diversity. The highest amount of available phosphorus (62.825 mg kg-1) in the district Swabi resulted in a low rate of AMF colonization (6.66 ± 11.54%) with a comparatively higher rate of AMF colonization (50.66 ± 1.15%) found in the soil of the district Chitral having a low phosphorus content (17.3 ± 7.6 mg kg-1). Nutrient uptake by pulses including nitrogen (2.4 ± 1.3%), phosphorus (13.5 ± 7.6 mg kg -1), potassium (99.5 ± 25.8 mg kg -1), zinc (1.4 ± 0.5 mg kg -1), moisture (2.3 ± 1.3%), crude fats (5.6 ± 2.8%), ash (4 ± 1.2%), and proteins (13.6 ± 9.01%) determined the fact that AMF species diversity is positively correlated to the plant mineral nutrition. From the current study, it is concluded that AMF inoculation to the soil fields is beneficial to ensure the sustainability and productivity of pulse crops in diverse environmental conditions without polluting the soil.

Cd contamination determined assembly processes and network stability of AM fungal communities in an urban green space ecosystem

The effects of cadmium (Cd) contamination on the assembly mechanism and co-occurrence patterns of arbuscular mycorrhizal (AM) fungal communities remain unclear, especially in urban green spaces. This study sequenced AM fungal communities in greenbelt soils in Zhengzhou (China). The effects of Cd contamination on the AM fungal diversity, community assembly processes, and co-occurrence patterns were explored. We found that (1) an increase in Cd contamination changed the community composition, which resulted in a significant improvement in the diversity of specialists of AM fungi and a significant decrease in the diversity of generalists. (2) Deterministic processes dominated the community assembly of specialists and stochastic processes dominated the community assembly of generalists. (3) Specialists played a more important role than generalists in maintaining the stability of AM fungal networks under Cd contamination. Overall, Cd contamination affected the ecological processes of AM fungi in urban green space ecosystems. However, the effects on the assembly processes and network stability of different AM fungi taxa (specialists and generalists) differed significantly. The present study provides deeper insight into the effect of Cd contamination on the ecological processes of AMF and is helpful in further exploring the ecological risk of Cd contamination in urban green spaces.

Plant-symbiotic fungal diversity tracks variation in vegetation and the abiotic environment along an extended elevational gradient in the Himalayas.

Arbuscular mycorrhizal (AM) fungi can benefit plants under environmental stress, and influence plant adaptation to warmer climates. However, very little is known about the ecology of these fungi in alpine environments. We sampled plant roots along a large fraction (1941-6150m asl) of the longest terrestrial elevational gradient on Earth and used DNA metabarcoding to identify AM fungi. We hypothesized that AM fungal alpha and beta diversity decreases with increasing elevation, and that different vegetation types comprise dissimilar communities, with cultured (putatively ruderal) taxa increasingly represented at high elevations. We found that alpha diversity of AM fungal communities declined linearly with elevation, whereas within-site taxon turnover (beta diversity) was unimodally related to elevation. Composition of AM fungal communities differed between vegetation types and was influenced by elevation, mean annual temperature and precipitation. In general, Glomeraceae taxa dominated at all elevations and vegetation types, however, higher elevations were associated with increased presence of Acaulosporaceae, Ambisporaceae and Claroideoglomeraceae. Contrary to our expectation, the proportion of cultured AM fungal taxa in communities decreased with elevation. These results suggest that, in this system, climate-induced shifts in habitat conditions may facilitate more diverse AM fungal communities at higher elevations but could also favour ruderal taxa.

Strong cooperations among diazotroph and arbuscular mycorrhizal fungi taxa promote free-living nitrogen fixation at soil-rock mixing layer

Soil nitrogen (N) is a renewable resource of N fixed by free-living N fixation (FLNF) diazotrophs. Thus, understanding the microbial driving mechanism of FLNF activity can aid in the optimization of N input. However, the role of co-symbiosis between diazotrophs and arbuscular mycorrhizal fungi (AMF) in the FLNF activity at different soil depths has been largely overlooked, particularly in karst ecosystems. Thus, we investigated soil properties and the characteristics of diazotroph and AMF across soil depths, from topsoil to soil-rock mixing layer, based on the soil profile. Soil properties such as soil organic matter and ammonium N decreased with increasing soil depth, whereas pH showed the opposite trend. Similarly, diazotroph abundance and diversity and AMF abundance were higher by 8–73% in 0–20 cm soil than in 20–40 cm and soil-rock mixing layer. Despite high diazotroph abundance in the topsoil, the FLNF activity was higher by 30% at soil-rock mixing layer than in 0–20 cm. The co-occurrence network analysis revealed a strengthening of the cooperative relationship between the diazotroph and AMF taxa at the soil-rock mixing layer via an increase in the number of unique AMF taxa. A structural equation model indicated that increasing soil depth improves the FLNF activity due to increasing soil pH and mutualistic cooperations between diazotrophs and AMF taxa, such as Bradyrhizobium to AMF unclassified taxa and Bradyrhizobium to Racocetra. This study provides novel insights into the interspecific interactions between diazotrophs and AMF, rather than their abundance and diversity, which were found to be the most important driving factors of FLNF activity at the soil-rock mixing layer. Consequently, the roles of biotic factors in influencing mutually beneficial microbial taxa regulating FLNF activity should be considered during vegetation recovery in the fragile karst region.

The plant–mycorrhizal fungi collaboration gradient depends on plant functional group

Abstract Plant colonization by arbuscular mycorrhizal fungi (AMF) is widespread and can offer considerable benefits in terms of growth, nutrient uptake and plant yield. However, it is still unresolved how different plant species and plant functional groups respond to AMF and to different AMF taxa. Here we established 336 grassland microcosms to determine the response of 14 plant species displaying contrasting functional groups (grasses, legumes and non‐leguminous forbs) for the presence of three different AMF taxa. For each plant species, we calculated the degree to which plant growth depended on AMF colonization (i.e. mycorrhizal dependency [MD]). We also determined the degree to which each plant species relied on specific AMF taxa for optimal growth (i.e. mycorrhizal species sensitivity [MSS]). Additionally, we determined whether MD and MSS correlated to specific plant traits (i.e. specific root length [SRL], specific leaf area [SLA]). The plant growth response to AMF ranged from −84.9% for a non‐mycorrhizal plant (Luzula campestris) to +94.0% for a legume (Trifolium arvensis). The MD was systematically higher in legumes (91.9% ± 2.4%), followed by non‐leguminous forbs (77.1% ± 11.06) and grasses (42.1% ± 15.73%). MSS was less variable (8.9%–37.7%); it was independent of plant functional group and did not correlate with MD. MD was linked to various mycorrhizal plant parameters, including AMF colonization (R2 = +0.80) and total dry biomass (R2 = +0.32). Moreover, among mycorrhizal plants (n = 12), MD negatively correlated with SRL (R2 = −0.24) and positively with SLA (R2 = +0.24). Synthesis. This study shows that plants relying on AMF for biomass production also show higher root colonization, lower SRL, higher SLA and that different plant traits are interlinked with the way how plants respond to AMF. Overall, this study further demonstrates that different plant functional groups vary in their response to AMF. Read the free Plain Language Summary for this article on the Journal blog.

Checklist of the arbuscular mycorrhizal fungi of Oaxaca, an important hotspot of biodiversity in Mexico

Background: Oaxaca, a southern State in Mexico, belongs to the Mesoamerican hotspot of biodiversity. The taxonomic and diversity knowledge of arbuscular mycorrhizal fungi (AMF) in Oaxaca State is scattered and accessibility to it is difficult.
 Questions: Which AMF species have been identified in Oaxaca and which is their distribution?
 Studied species: Arbuscular mycorrhizal fungi.
 Study site: State of Oaxaca, Mexico.
 Methods: It was prepared an updated and annotated checklist of the AMF species with frequency of occurrence and the sampling sites where the species had been registered. All studies carried out previously (to date, 2022) were considered. Information on AMF taxa was available in scattered form in different publications in physical and electronic media, theses, projects, technical reports, and scientific papers.
 Results: The checklist includes 78 species, distributed among 23 genera, 10 families, and four orders. The most diverse families were Glomeraceae (26 species), followed by Gigasporaceae (20) and Acaulosporaceae (15), whereas the most diverse genera were Acaulospora and Glomus (15 and eight species, respectively). The most frequent species were Funneliformis geosporus, Acaulospora scrobiculata, and A. spinosa. The highest species diversity has been reported under the rhizosphere of Agave angustifolia, A. karwinskii, and Zea mays (39, 36, and 34 species, respectively). A new AMF species was recently isolated from the rhizosphere of a microendemic agave.
 Conclusions: The recorded AMF species of Oaxaca State confirms its position as one of the states with the highest AMF species diversity of Mexico.

Spore traits mediate disturbance effects on arbuscular mycorrhizal fungal community composition and mutualisms.

Trait-based approaches in ecology are powerful tools for understanding how organisms interact with their environment. These approaches show particular promise in disturbance and community ecology contexts for understanding how disturbances like prescribed fire and bison grazing influence interactions between mutualists like arbuscular mycorrhizal (AM) fungi and their plant hosts. In this work we examined how disturbance effects on AM fungal spore community composition and mutualisms were mediated by selection for specific functional spore traits at both the species and community level. We tested these questions by analyzing AM fungal spore communities and traits from a frequently burned and grazed (bison) tallgrass prairie system and using these spores to inoculate a plant growth response experiment. Selection for darker, pigmented AM fungal spores, changes in the abundance and volume of individual AM fungal taxa, and altered sporulation, were indicators of fire and grazing effects on AM fungal community composition. Disturbance associated changes in AM fungal community composition were then correlated with altered growth responses of Schizachyrium scoparium grass. Our work shows that utilization of trait-based approaches in ecology can clarify the mechanisms that underly belowground responses to disturbance, and provide a useful framework for understanding interactions between organisms and their environment.

Ecological drivers of fine-scale distribution of arbuscular mycorrhizal fungi in a semiarid Mediterranean scrubland.

Arbuscular mycorrhizal (AM) fungi enhance the uptake of water and minerals by the plant hosts, alleviating plant stress. Therefore, AM fungal-plant interactions are particularly important in drylands and other stressful ecosystems. We aimed to determine the combined and independent effects of above- and below-ground plant community attributes (i.e. diversity and composition), soil heterogeneity and spatial covariates on the spatial structure of the AM fungal communities in a semiarid Mediterranean scrubland. Furthermore, we evaluated how the phylogenetic relatedness of both plants and AM fungi shapes these symbiotic relationships. We characterized the composition and diversity of AM fungal and plant communities in a dry Mediterranean scrubland taxonomically and phylogenetically, using DNA metabarcoding and a spatially explicit sampling design at the plant neighbourhood scale. The above- and below-ground plant community attributes, soil physicochemical properties and spatial variables explained unique fractions of AM fungal diversity and composition. Mainly, variations in plant composition affected the AM fungal composition and diversity. Our results also showed that particular AM fungal taxa tended to be associated with closely related plant species, suggesting the existence of a phylogenetic signal. Although soil texture, fertility and pH affected AM fungal community assembly, spatial factors had a greater influence on AM fungal community composition and diversity than soil physicochemical properties. Our results highlight that the more easily accessible above-ground vegetation is a reliable indicator of the linkages between plant roots and AM fungi. We also emphasize the importance of soil physicochemical properties in addition to below-ground plant information, while accounting for the phylogenetic relationships of both plants and fungi, because these factors improve our ability to predict the relationships between AM fungal and plant communities.

Effects of pavements on diversity and activity of mycorrhizal symbionts associated with urban trees

This study investigated the impact of different types of soil sealing on the communities of a group of beneficial plant symbionts, arbuscular mycorrhizal fungi (AMF), colonizing the roots of two shade trees, Celtis australis and Fraxinus ornus, frequently grown in urbanized sites. Such plants were grown in an experimental site, in northern Italy, established in November 2011 and subjected to four different pavement treatments: impermeable monolithic asphalt, permeable pavers, permeable concrete and unpaved soil. The diversity and composition of root AMF communities were assessed by PCR denaturating gradient gel electrophoresis of partial 18S rRNA gene, AMF taxa were identified by amplicon sequencing and mycorrhizal colonization was evaluated after root clearing and staining. For the first time, our molecular work revealed that impermeable pavements induced shifts in the composition of AMF communities associated to the roots of C. australis and F. ornus and impacted on the percentage of mycorrhizal root length. When the root-zone was covered with permeable pavements, a similar AMF community as that observed in the unpaved soil was detected, providing novel information to be utilised for reducing the disturbance caused by specific types of soil sealing on AMF symbionts, which play a key role in plant nutrition and health. A total of 45 AMF sequence types were detected, with Sclerocystis and Septoglomus as the most abundant phylotypes, accounting for 84% of the sequences. The predominance of Sclerocystis species in the roots of both tree species under impermeable pavements indicated their high and unforeseen tolerance towards harsh environmental conditions. Such species could be utilized as AMF inocula specifically selected for their proven resilience in paved sites, in order to exploit their ability to boost biogeochemical processes fundamental for energy fluxes and plant nutrition and health.

Synergistic effects of diazotrophs and arbuscular mycorrhizal fungi on soil biological nitrogen fixation after three decades of fertilization

AbstractBiological nitrogen (N) fixation (BNF) via diazotrophs is an important ecological process for the conversion of atmospheric N to biologically available N. Although soil diazotrophs play a dominant role in BNF and arbuscular mycorrhizal fungi (AMF) serve as helpers to favor BNF, the response of soil BNF and diazotrophic communities to different long‐term fertilizations and the role of AMF in diazotrophs‐driven BNF are poorly understood. Herein, a 33‐year fertilization experiment in a wheat–maize intercropping system was conducted to investigate the changes in soil BNF rates, diazotrophic and AMF communities, and their interactions after long‐term representative fertilization (chemical fertilizer, cow manure, wheat straw, and green manure). We found a remarkable increase in soil BNF rates after more than three decades of fertilization compared with nonfertilized soil, and the green manure treatment rendered the highest enhancement. The functionality strengthening was mainly associated with the increase in the absolute abundance of diazotrophs and AMF and the relative abundance of the key ecological cluster of Module #0 (gained from the co‐occurrence network of diazotrophic and AMF species) with dominant diazotrophs such as Skermanella and Azospirillum. Furthermore, although the positive correlations between diazotrophs and AMF were reduced under long‐term organic fertilization regimes, green manuring could reverse the decline within Module #0, and this had a positive relationship with the BNF rate. This study suggests that long‐term fertilization could promote N fixation and select specific groups of N fixers and their helpers in certain areas. Our work provides solid evidence that N fixation and certain groups of diazotrophic and AMF taxa and their interspecies relationship will be largely favored after the fertilized strategy of green manure.

Stochastic processes dominate soil arbuscular mycorrhizal fungal community assembly along an elevation gradient in central Japan

Arbuscular mycorrhizal (AM) fungi play an important role in facilitating ecosystem function and stability. Yet, their community response patterns and ecological assembly processes along elevational gradients which cross a range of climates and soil conditions remain elusive. We used Illumina MiSeq sequencing to examine trends in soil AM fungal community along an elevational gradient from 100 m to 2300 m in central Japan. A total of 750 operational taxonomic units (OTUs) affiliated to 12 AM fungal genera were identified from soil samples, and the AM fungal community composition differed strongly with elevation, with variance explained more by climate, followed by soil and plant factors. The AM fungal α-diversity, network connectivity and complexity between AM fungal taxa and also with plant communities all exhibited a maximum at the mid-elevation of 800 m and then declined, principally influenced by soil pH and precipitation. Stochastic processes dominated AM fungal community assembly across the whole elevation gradient, with homogenizing dispersal being the main process. Only when AM fungal communities were contrasted across a relatively broad range of elevations, did variable selection (deterministic process) became significant, and even then in a mixed role with stochasticity. While OTUs of AM fungi are clearly adapted to particular environmental ranges, stochasticity due to rapid dispersal has a major role in determining their occurrence, suggesting that AM fungi may possess generalized and interchangeable niches, and can adjust their distribution rapidly - at least on the scale of a single mountain. This finding emphasizes that the roles of AM fungi in plant ecology may be non-specific and easily substituted, and furthermore that there is rapid local scale dispersal, which may allow plants to maintain effective AM associations under environmental change.

Hedgerows increase the diversity and modify the composition of arbuscular mycorrhizal fungi in Mediterranean agricultural landscapes

Sustainable agriculture is essential to address global challenges such as climate change and biodiversity loss. Hedgerows enhance aboveground biodiversity and provide ecosystem services, but little is known about their impact on soil biota. Arbuscular mycorrhizal (AM) fungi are one of the key components of belowground biodiversity. We compared the diversity and composition of AM fungal communities at four farmland sites located in Central Spain, where 132 soil samples in total were collected to assess soil physical and chemical properties and the AM fungal communities. We compared the richness (number of AM fungal taxa), taxonomic, functional, and phylogenetic diversity, and structure of the AM fungal communities across three farmland habitat types, namely hedgerows, woody crops (olive groves and vineyard), and herbaceous crops (barley, sunflower, and wheat). Our results showed positive effects of hedgerows on most diversity metrics. Almost 60% of the AM fungal taxa were shared among the three farmland habitat types. Hedgerows increased AM fungal taxonomic richness (31%) and alpha diversity (25%), and especially so compared to herbaceous crops (45% and 28%, respectively). Hedgerows harbored elevated proportions of AM fungi with non-ruderal life-history strategies. AM fungal communities were more similar between hedgerows and woody crops than between hedgerows and adjacent herbaceous crops, possibly because of differences in tillage and fertilization. Unexpectedly, hedgerows reduced phylogenetic diversity, which might be related to more selective associations of AM fungi with woody plants than with herbaceous crops. Overall, the results suggest that planting hedgerows contributes to maintain belowground diversity. Thus, European farmers should plant more hedgerows to attain the goals of the EU Biodiversity Strategy for 2030.