Arbuscular Mycorrhizal Fungi Assemblages Research Articles

Rainfall and soil properties driver the temporal dynamics of arbuscular mycorrhizal fungal assemblages in a seasonally dry tropical forest

The Seasonally Dry Tropical Forests (SDTF), distributed from Mexico to northern Argentina, are habitat to a unique biodiversity. Among these forests, the Caatinga stands out, occupying a large part of the Brazilian Northeast and is subject to cycles of anthropic disturbance and abandonment of exploited areas. Understanding how microbial communities respond to environmental changes is crucial, especially considering the various ecosystem services provided by microorganisms. Among soil microorganisms, arbuscular mycorrhizal fungi (AMF) play a significant role in the maintenance of terrestrial ecosystems. In this study, we aimed to evaluate the structure, composition, and distribution of AMF assemblages, as well as their main drivers, in regeneration areas of the Caatinga. Soil samples were collected in the Catimbau National Park (Pernambuco State), including an old-growth forest representing undisturbed areas, and in early, intermediate, and late regeneration areas. The composition of AMF assemblages differed among regenerating areas and old-growth forest, but their distribution is not related and conditioned to plant assemblages. Instead, soil properties and rainfall are the main factors structuring these assemblages in SDTF. A total of 83 taxa of AMF were identified. Glomus and Acaulospora, which exhibit respectively ruderal and stress-tolerant life strategies were the most abundant genera. The highest number of unique AMF species was recorded in the old-growth forest, contrasting with the late regeneration areas which had the lowest number. The results showed that deterministic processes (soil and rainfall) are structuring the AMF assemblages in areas under regeneration process in SDTF. Plants and AMF do not recover simultaneously over the evaluated regeneration times.

Year-round dynamics of arbuscular mycorrhizal fungi communities in the roots and surrounding soils of Cryptomeria japonica

Arbuscular mycorrhizal fungi (AMF) live simultaneously inside and outside of host plant roots for a functional mycorrhizal symbiosis. Still, the year-round dynamics and relationships between soil properties and AMF communities of trees in forest ecosystems remain unclear. We collected paired root and soil samples of the same Cryptomeria japonica trees at two forest sites (five trees at each site) every 2 months over a year. Total DNA was extracted from roots and soil separately and soil physicochemical properties were measured. With Illumina’s next-generation amplicon sequencing targeting the small subunit of fungal ribosomal DNA, we clarified seasonal dynamics of soil properties and AMF communities. Soil pH and total phosphorus showed significant seasonality while total carbon, nitrogen, and C/N did not. Only pH was a good predictor of the composition and dynamics of the AMF community. The total AMF community (roots + soil) showed significant seasonality because of variation from May to September. Root and soil AMF communities were steady year-round, however, with similar species richness but contained significantly different AMF assemblages in any sampling month. Despite the weak seasonality in the communities, the top two dominant OTUs showed significant but different shifts between roots and soils across seasons with strong antagonistic relationships. In conclusion, few dominant AMF taxa are dynamically shifting between the roots and soils of C. japonica to respond to seasonal and phenological variations in their microhabitats. AMF inhabiting forest ecosystems may have high environmental plasticity to sustain a functional symbiosis regardless of seasonal variations that occur in the soil.

Responses of the arbuscular mycorrhizal fungi community to warming coupled with increased drought in an arid desert region

Warming coupled with precipitation changes induced by climate change profoundly affect desert ecosystem functions in global drylands. Arbuscular mycorrhizal fungi (AMF) play a crucial role in such ecosystems by regulating energy and nutrient exchange. However, little is known about how AMF communities respond to warming coupled with reduced precipitation (W + RP). We evaluated the impacts of 0.5 °C and 1.5 °C increase in temperature coupled with 5 % and 8 % reductions in total annual precipitation (0.5 °C W + 5 % RP, 1.5 °C W + 8 % RP) on AMF communities and the main ecological processes structuring AMF community assemblies in the rhizosphere soil of typical winter annual plants in the Tengger Desert, northwest China. The results showed that warming coupled with reduced precipitation could significantly alter the composition, abundance, and diversity of AMF communities. Both AMF biomass and AMF diversity increased in the 0.5 °C W + 5 % RP treatment but decreased in the 1.5 °C W + 8 % RP treatment. The 1.5 °C W + 8 % RP treatment significantly reduced root biomass and the AMF colonization rate but increased the specific root length, indicating a trade-off between fine roots and their symbiotic AMF. The AMF community was phylogenetically random in the 0.5 °C W + 5 % RP treatment but appeared clustered in the 1.5 °C W + 8 % RP treatment, implying that more pronounced warming coupled with reduced precipitation can promote the deterministic assembly of the AMF community. We provide a conceptual framework for comprehending the mechanisms underlying the effects of warming coupled with reduced precipitation on AMF communities, incorporating biological and geochemical processes. Overall, the findings of this study suggest that AMF abundance and diversity and the main ecological processes driving AMF assemblages respond differently to more pronounced compared to less intensive warming coupled with reduced precipitation. Importantly, higher warming coupled with a reduction in precipitation reduced plant dependence on AMF and resulted in stronger environmental filtration by significantly reducing soil water content.

A trade-off between space exploration and mobilization of organic phosphorus through associated microbiomes enables niche differentiation of arbuscular mycorrhizal fungi on the same root.

Ecology seeks to explain species coexistence, but experimental tests of mechanisms for coexistence are difficult to conduct. We synthesized an arbuscular mycorrhizal (AM) fungal community with three fungal species that differed in their capacity of foraging for orthophosphate (P) due to differences in soil exploration. We tested whether AM fungal species-specific hyphosphere bacterial assemblages recruited by hyphal exudates enabled differentiation among the fungi in the capacity of mobilizing soil organic P (Po). We found that the less efficient space explorer, Gigaspora margarita, obtained less 13C from the plant, whereas it had higher efficiencies in Po mobilization and alkaline phosphatase (AlPase) production per unit C than the two efficient space explorers, Rhizophagusintraradices and Funneliformis mosseae. Each AM fungus was associated with a distinct alp gene harboring bacterial assemblage, and the alp gene abundance and Po preference of the microbiome associated with the less efficient space explorer were higher than those of the two other species. We conclude that the traits of AM fungal associated bacterial consortia cause niche differentiation. The trade-off between foraging ability and the ability to recruit effective Po mobilizing microbiomes is a mechanism that allows co-existence of AM fungal species in a single plant root and surrounding soil habitat.

Belowground crop responses to root herbivory are associated with the community structure of native arbuscular mycorrhizal fungi

There is growing interest in managing arbuscular mycorrhizal (AM) fungi in agriculture to support plant production. These fungi can support crop growth and nutrient uptake, but also affect plant-herbivore interactions. While our understanding of how AM fungi affect plant responses to herbivory advances, it is less clear how different naturally-occurring (native) fungal communities differentially influence crop responses to root-feeding insects.To explore this, plants (Sorghum bicolor) were grown in a glasshouse experiment without AM fungi (‘no AM fungi’) or with one of three natural soil inocula sourced either from a sclerophyll forest (‘forest inoculum’), a cropped field (‘field inoculum’), or a field in fallow (‘fallow inoculum’), while half the plants were subjected to a root herbivore (Dermolepida albohirtum). We assessed the effects of soil inoculum and root herbivory on root-colonising AM fungal diversity, plant growth, and nutrient content.Root herbivory did not affect AM fungal diversity or composition. Plants grown with the field or fallow inocula were both dominated by the genera Glomus and Claroideoglomus. These plants exhibited reduced biomass in response to inoculation, but were not impacted by root herbivory. In contrast, plants with the forest inoculum had AM fungal communities dominated by Paraglomus and Ambispora. When subjected to root herbivory, the forest inoculated plants and plants without AM fungi exhibited reductions of 44 % and 61 % in root biomass, and reductions of 65 % and 59 % in root phosphorus, respectively.Our study shows inoculation-driven plant responses to root herbivory that were associated with the community structure of their root-colonising AM fungi. Results suggest associations with communities dominated by Claroideoglomus and Glomus may mitigate the impacts of a root-feeding insect. More exploration of how natural assemblages of AM fungi mediate plant-herbivore interactions is needed if we are to effectively manage soil fungi in agriculture.

Host plant richness and environment in tropical forest transformation systems shape arbuscular mycorrhizal fungal richness.

Transformation of tropical lowland rain forests into rubber tree and oil palm plantations is the cause of massive loss of vegetation diversity. The consequences for associated mycorrhizal fungi are not fully understood. We hypothesized that generalist arbuscular mycorrhizal fungi are resistant to removal of host species richness and that forest conversion to oil palm and rubber leads to loss of arbuscular mycorrhizal fungal (AMF) species with host preferences. Plant identities and AMF species were determined by molecular barcoding of 112 roots collected in three land-use systems (rain forest, rubber tree and oil palm plantation) in two landscapes on Sumatra (Indonesia), a world hotspot of forest transformation. The collected roots were from 43 forest plant species, in addition to rubber trees and oil palms. We detected 28 AMF species of which about 75% were present in forest trees and 25% shared among the land use systems. Only one AMF species present in plantation roots was not detected in the analyzed forest roots. Host specificity of arbuscular mycorrhizal fungi was not detected. Oil palm and rubber tree roots exhibited a strong reduction in AMF richness compared with roots from rainforests and were differentiated by soil resources. On basis of an individual root, oil palm had a lower AMF species richness than forest or rubber tree roots. Our results demonstrate that tropical AMF communities are shaped by two mechanisms: (i) root habitat diversity as the result of plant diversity and (ii) habitat properties as the result of plant traits or environmental conditions and management. Collectively, deterioration of habitat diversity and properties exacerbates impoverishment of AMF assemblages.

The root-associated arbuscular mycorrhizal fungal assemblages of exotic alien plants are simplified in invaded distribution ranges, but dominant species are retained: A trans-continental perspective.

Arbuscular mycorrhizal fungi (AMF) provide crucial support for the establishment of plants in novel environments. We hypothesized that the OTU/genus richness and diversity of soil- and root-associated AMF associated with alien plant species in their exotic ranges are lower than those in their native ranges. We examined the root-associated and soil-dwelling AMF of 11 invasive plant species in their native and exotic ranges in the United States and Europe by DNA sequencing of the ITS2 locus. Examined root-associated AMF assemblages were simplified, which manifested as the loss of several AMF genera in the exotic ranges of the plants. These fungal assemblages were also characterized by greater dominance and simplification of the fungal assemblages. The dominant fungal genera were present regardless of whether their host plants were in their native or exotic ranges. Interestingly, both the native and invaded soils hosted diverse local AMF assemblages. Therefore, alien plant invasions were not limited to soils with low AMF diversity. Some AMF taxa could be context-dependent passengers rather than drivers of alien plant invasions. Further studies should identify functions of AMF missing or less abundant in roots of plants growing in exotic ranges.

Microbial inoculation and fertilizer application on growth of cowpea and spore-based assemblages of arbuscular mycorrhizal fungi in its rhizophere.

In this study, the effect of microbial inoculants and fertilizer application on cowpea (BRS Pujante) growth and on the structure and composition of arbuscular mycorrhizal fungi (AMF) assemblages were evaluated. A completely randomized experiment was set up involving 17 treatments: four with AMF, three with nodulating bacteria, six with AMF + nodulating bacteria, two with phosphorus, one with nitrogen and one control (reference) in five replicates. Plant growth and nutritional content, mycorrhizal colonization, glomerospores number, spore-based AMF assemblages and ecological indices were evaluated. Mycorrhizal inoculants associated with Bradyrhizobium BR3267 strain were more effective than the Microvirga BR3296 strain. Multidimensional scaling analysis showed that Acaulospora longula treatments were more similar among themselves, and distinct from the other treatments. A difference was observed in the structure of AMF community assemblage between treatments with G. albida + Bradyrhizobium BR 3267 and A. longula, with greater Shannon diversity and Pielou equitability indices in the first treatment and greater dominance in the treatment with A. longula only. Long-term studies are required to determine if the successful establishment of A. longula among indigenous species persists over time and if its dominant behavior is not deleterious to the AMF native community.

Diversity of arbuscular mycorrhizal fungi and its chemical drivers across dryland habitats.

Qatar is largely characterized by a hyper-arid climate and low soil fertility which create a stressful soil environment for arbuscular mycorrhizal (AM) fungi. In a study of AM fungal communities and their relationship with soil chemical characteristics, we used a high-throughput sequencing technique to explore AM fungal diversity and community composition in different habitats across Qatar. We identified a total of 79 AM fungal taxa, over 77% of which were species from the Glomeraceae family. The lowest AM fungal diversity was observed in saltmarsh and in one rawdha site, while the highest richness, effective number of species, and diversity were observed in rawdha and sabkha communities. NMDS and multiple regression analyses showed that AM fungi were negatively correlated with soil pH and TC, but positively correlated with K and NO3-. AM fungi also were positively correlated with Cd, with the latter suggesting that very low levels of heavy metals may not always be harmful to AM fungi. These findings provide baseline information on AM fungal assemblages and the chemical drivers of diversity across communities in Qatar. This work partly compensates for the current lack of broad-scale studies in the Arabian Peninsula by providing understanding of overall patterns of AM fungi and their drivers in the region.

Micro-Landscape Dependent Changes in Arbuscular Mycorrhizal Fungal Community Structure

The roots of most plants host diverse assemblages of arbuscular mycorrhizal fungi (AMF), which benefit the plant hosts in diverse ways. Even though we understand that such AMF assemblages are non-random, we do not fully appreciate whether and how environmental settings can make them more or less predictable in time and space. Here we present results from three controlled experiments, where we manipulated two environmental parameters, habitat connectance and habitat quality, to address the degree to which plant roots in archipelagos of high connectance and invariable habitats are colonized with (i) less diverse and (ii) easier to predict AMF assemblages. We observed no differences in diversity across our manipulations. We show, however, that mixing habitats and varying connectance render AMF assemblages less predictable, which we could only detect within and not between our experimental units. We also demonstrate that none of our manipulations favoured any specific AMF taxa. We present here evidence that the community structure of AMF is less responsive to spatio-temporal manipulations than root colonization rates which is a facet of the symbiosis which we currently poorly understand.

Molecular diversity of arbuscular mycorrhizal fungi associated with two alpine plant species in the Tibetan Plateau

Alpine ecosystem in the Tibetan Plateau has a special ecological environment, which may harbor a high richness of arbuscular mycorrhizal fungi (AMF) communities. To explore the molecular diversity of AMF community associated with plants in alpine grasslands, root and rhizosphere soil of two dominant plant species, Kobresia sp. and Leontopodium pusillum in Qinghai province, were studied by molecular biotechnology (clone library and sequencing) at five sites for each plant species. A total of 30 operational taxonomic units (OTUs) were identified, including seven families of Glomeromycota. Glomeraceae and Glo1 and Glo2 were most abundant at family and OUT level in roots respectively, while both Glomeraceae and Diversisporaceae were frequently present and Glo1 and Div1 were the most dominant OTUs in the soil. The AMF community was different in the roots and soil. Nineteen OTUs were identified in the roots of Kobresia sp., and 21 OTUs were identified in the rhizosphere soil. As to L. pusillum, fourteen OTUs were identified in roots and 17 OTUs in the soil. Specifically, three OTUs were only found in L. pusillum, and eight OTUs were only found in Kobresia sp. The root biomass and soil C/N ratio were the main factors affecting the AMF community in roots, whereas in soil, the important factors were root carbon content and shoot nitrogen content. These results showed a high diversity of AMF associated with the typical alpine plants, and distinct AMF community exist in roots and soil. Our results confirmed the importance of plant and soil factors in driving AMF assemblages in the fragile ecosystem of Tibetan Plateau.

Plant neighbours shape fungal assemblages associated with plant roots: A new understanding of niche‐partitioning in plant communities

Abstract Understanding the assembly rules of mycorrhizal fungi is crucial, given their tremendous importance in plant nutrition and health. Differentiation in plant‐associated arbuscular mycorrhizal fungi (AMF) is likely driven by a host‐preference effect. Coexisting plant species may then affect a focal plant microbiota through fungal dispersal among plants, and plant preferential recruitment of AMF. Both mechanisms are likely shaped by the plant's phylogenetic and functional strategies. We expected that (a) the structure of AMF assemblages associated with a focal plant depends on the identity of the neighbouring plant species; (b) this effect would be predicted by the phylogenetic and functional similarity between the focal and neighbouring plant species. These predictions were tested during the first stages of growth, by simulating the early development of plants within a community Using an experimental matrix‐focal plant species design testing 15 neighbouring plants from five taxonomic families, we demonstrated that the neighbouring plants provided different species pools for the focal plant, Medicago truncatula, and influenced AMF communities associated with focal plant, especially in terms of richness but not relative evenness. Medicago truncatula grown with Brassicaceae or other Poaceae species displayed respectively no or low AMF richness compared to those grown with Rosaceae and Asteraceae species. These effects were weakly dependent on the phylogenetic distance from the neighbouring plant but were predicted by the functional proximity. AMF assemblages were enriched and bore more resemblance to the neighbouring plants when the neighbouring plants were functionally dissimilar from the focal one. Functional dissimilarity was only a significant predictor when based on traits characterizing the nutrient use and uptake strategy rather than on a more integrated growing strategy of the plant. Microbiota composition was shown to be dependent on the identity of the neighbouring plant, particularly on its functional below‐ground niche. At the colonization stage, when the plant arrives in a community, plant mycobiota might be influenced by the spatial distribution of plants already present in the community. This work suggests a new view of the concept of niche partitioning in space for plants based on microorganism–plant interactions. A free Plain Language Summary can be found within the Supporting Information of this article.

Biocrusts inside and outside of Mimosa luisana resource islands as reservoirs of arbuscular mycorrhizal fungi in a Mexican semiarid ecosystem

Background: Arbuscular mycorrhizal fungi (AMF) and biocrusts (BC), occur inside and outside Mimosa luisana resource islands (M. luisana-RI) at the Tehuacán-Cuicatlán Valley, Puebla-Oaxaca, Mexico.
 Objectives: To determine: 1) Whether there are AMF within biocrusts, 2) The abundance and richness of AMF, and 3) The potential of AMF propagation in BC and soil below BC inside (BC-RI, soil-BC-RI) and outside (BC-ORI, soil-BC-ORI) M. luisana-RI, and open areas (OA), in the rainy (September 2011) and dry (May 2012) seasons.
 Methods: AMF were extracted of biocrusts and soil samples collected inside and outside M. luisana-RI and OA, in both seasons. Spore abundance and species richness, as well as potential propagation of AMF were determined in laboratory and greenhouse.
 Results and Conclusions: Biocrusts inside and outside M. luisana-RI form reservoirs of AMF spores and species richness (12 spp.), and act as “shields” protecting AMF compared with OA (5 spp.). Seasonal changes in the AMF composition within the biocrusts and the soil suggest that the availability of water drives AMF assemblages. The AM fungal spores in BC-RI and BC-ORI have a high potential of propagation; however, the BC-ORI by buffering the loss of AMF in soil-BC-ORI, they form mycorrhizal inocula within the soil.

Arbuscular Mycorrhizal Fungal Assemblages in Conservation Unit of Atlantic Forest Areas Under Native Vegetation and Natural Regeneration.

Arbuscular mycorrhizal fungi (AMF) play an important role in the dynamic of plant community in the south American Atlantic Rainforest biome. Even in protected areas, this biome is under several anthropic impacts, which can cause shifts in the soil microbiota, including AMF. This study aimed to determine the structure and composition of AMF community in areas of native Atlantic Forest and in natural regeneration and to identify which abiotic factors are influencing this community in these areas. Soil samples were collected at Monte Pascoal National and Historical Park, in Southern Bahia, in native and natural regeneration areas of Atlantic Forest in two seasons (rainy and dry). Greater number of glomerospores and richness and diversity of AMF were found in the area under regeneration, with differences between seasons being observed only for the number of glomerospores. Seventy-seven species of AMF were recorded, considering all areas and seasons, with Acaulospora and Glomus being the most representative genera. Greater abundance of species of the genera Acaulospora, Claroideoglomus, and Septoglomus was found in the regeneration area. The AMF community differed between the study areas, but not between seasons, with soil attributes (pH, K, Al, Mg, m, and clay) structuring factors for this difference in the AMF community. Atlantic Forest areas in natural regeneration and the soil edaphic factors provide changes in the structure and composition of the AMF community, increasing the richness and diversity of these fungi in conservation units.

An invasive plant rapidly increased the similarity of soil fungal pathogen communities.

Plant invasions can change soil microbial communities and affect subsequent invasions directly or indirectly via foliar herbivory. It has been proposed that invaders promote uniform biotic communities that displace diverse, spatially variable communities (the biotic homogenization hypothesis), but this has not been experimentally tested for soil microbial communities, so the underlying mechanisms and dynamics are unclear. Here, we compared density-dependent impacts of the invasive plant Alternanthera philoxeroides and its native congener A. sessilis on soil fungal communities, and their feedback effects on plants and a foliar beetle. We conducted a plant-soil feedback (PSF) experiment and a laboratory bioassay to examine PSFs associated with the native and invasive plants and a beetle feeding on them. We also characterized the soil fungal community using high-throughput sequencing. We found locally differentiated soil fungal pathogen assemblages associated with high densities of the native plant A. sessilis but little variation in those associated with the invasive congener A. philoxeroides, regardless of plant density. In contrast, arbuscular mycorrhizal fungal assemblages associated with high densities of the invasive plant were more variable. Soil biota decreased plant shoot mass but their effect was weak for the invasive plant growing in native plant-conditioned soils. PSFs increased the larval biomass of a beetle reared on leaves of the native plant only. Moreover, PSFs on plant shoot and root mass and beetle mass were predicted by different pathogen taxa in a plant species-specific manner. Our results suggest that plant invasions can rapidly increase the similarity of soil pathogen assemblages even at low plant densities, leading to taxonomically and functionally homogeneous soil communities that may limit negative soil effects on invasive plants.

Arbuscular Mycorrhizal Fungal Assemblages Significantly Shifted upon Bacterial Inoculation in Non-Contaminated and Petroleum-Contaminated Environments.

Arbuscular mycorrhizal fungi (AMF) have been shown to reduce plant stress and improve their health and growth, making them important components of the plant-root associated microbiome, especially in stressful conditions such as petroleum hydrocarbons (PHs) contaminated environments. Purposely manipulating the root-associated AMF assemblages in order to improve plant health and modulate their interaction with the rhizosphere microbes could lead to increased agricultural crop yields and phytoremediation performance by the host plant and its root-associated microbiota. In this study, we tested whether repeated inoculations with a Proteobacteria consortium influenced plant productivity and the AMF assemblages associated with the root and rhizosphere of four plant species growing either in non-contaminated natural soil or in sediments contaminated with petroleum hydrocarbons. A mesocosm experiment was performed in a randomized complete block design in four blocks with two factors: (1) substrate contamination (contaminated or not contaminated), and (2) inoculation (or not) with a bacterial consortium composed of ten isolates of Proteobacteria. Plants were grown in a greenhouse over four months, after which the effect of treatments on plant biomass and petroleum hydrocarbon concentrations in the substrate were determined. MiSeq amplicon sequencing, targeting the 18S rRNA gene, was used to assess AMF community structures in the roots and rhizosphere of plants growing in both contaminated and non-contaminated substrates. We also investigated the contribution of plant identity and biotope (plant roots and rhizospheric soil) in shaping the associated AMF assemblages. Our results showed that while inoculation caused a significant shift in AMF communities, the substrate contamination had a much stronger influence on their structure, followed by the biotope and plant identity to a lesser extent. Moreover, inoculation significantly increased plant biomass production and was associated with a decreased petroleum hydrocarbons dissipation in the contaminated soil. The outcome of this study provides knowledge on the factors influencing the diversity and community structure of AMF associated with indigenous plants following repeated inoculation of a bacterial consortium. It highlights the dominance of soil chemical properties, such as petroleum hydrocarbon presence, over biotic factors and inputs, such as plant species and microbial inoculations, in determining the plant-associated arbuscular mycorrhizal fungi communities.

Tropical forest type influences community assembly processes in arbuscular mycorrhizal fungi

AbstractAimPlant community assembly in tropical rain forest has been shown to be largely governed by stochastic processes, but as arbuscular mycorrhizal (AM) fungi display limited host preference, they may not follow the same stochastic assembly pattern. Here, we determined the relative importance of environmental and spatial drivers responsible for the community assembly process of AM fungi in two types of tropical rain forest: semideciduous rain forest and dense ombrophilous forests.LocationAtlantic rain forest in north‐eastern Brazil, South America.TaxonArbuscular mycorrhizal fungi (Glomeromycotina).MethodsWe collected root samples from eight protected areas of Atlantic forest along a 700 km transect in north‐eastern Brazil. We measured the relative importance of deterministic and stochastic processes by redundancy analysis (RDA) and variation partitioning in comparison with null expectations using ad hoc generated neutral communities. Furthermore, we accessed species associations from co‐occurrence data, at different scales using a Bayesian approach of Hierarchical Modelling of Species Communities.ResultsOverall, the extent to which stochastic and deterministic processes affected community assembly depended on the forest type and the spatial scale. Specifically, we found that abiotic and biotic predictors of AM fungal community assemblages are related to environmental homogeneity in tropical rain forests.Main conclusionsThe results of the study show that dynamics in community assembly was clearly different between the two forest types, and that the difference most likely is due to differences in responses to environmental variables.

Biogeography of arbuscular mycorrhizal fungal communities in saline ecosystems of northern China

Arbuscular mycorrhizal (AM) fungi, influencing many important ecosystem processes, widely occur in saline soils, and thus understanding their biogeographic patterns is of primary interest in saline ecosystem restoration. Fine roots and rhizosphere soils were sampled in black locust (Robinia pseudoacacia) plantations in four saline sites in northern China to detect soil properties and AM fungal attributes including their colonization level, spore density, hyphal density and community composition. Arbuscular mycorrhizal fungal attributes varied with sampling sites, and this variation was mostly attributed to changes in habitat characteristics and geographic distance. Habitat characteristics shape the root- and soil-inhabiting AM fungal communities to the same extent, whereas geographic distance seems to contribute more to root-inhabiting AM fungal assemblages. The level of root colonization by vesicles, arbuscules and hyphae and the density of AM fungal spores and hyphae in soils were found to be related to the relative abundance of AM fungal species such as root-inhabiting Rhizophagus intraradices and soil-inhabiting Sclerocystis sinuosa. All the results suggest that changes in habitat characteristics and geographic distance may induce biogeographic patterns of AM fungi, and these patterns are closely related to AM symbiosis in roots and the development of AM fungi in soils.

Assemblages of arbuscular mycorrhizal fungi in tropical humid and dry forests in the Northeast of Brazil

Tropical forests concentrate most of the world’s biodiversity. In the Northeast of Brazil it is possible to record mosaics of tropical dry and moist forests growing nearby but with completely different biotic and abiotic characteristics. These forests are constantly threatened by intense environmental devastation that affect not only above-ground communities but also those hidden below-ground, such as arbuscular mycorrhizal fungi (AMF), which act in maintaining ecosystem balance. This work aimed to determine the composition of native AMF communities in areas of humid forest (HF) and dry forest (DF) in northeastern Brazil. A total of 70 taxa of AMF were identified in the study areas, with Acaulospora (17) and Glomus (16) being the most representative genera. The sampling effort allowed the evaluation of 70%–73% of the species estimated for the areas. AMF communities differed between HF and DF areas. Species of the genus Glomus occurred predominantly in humid forest areas, whereas representatives of the order Gigasporales were associated more specifically with the dry forest area. Four soil attributes showed approximately 50% correlation with the composition of the AMF community (silt, clay, K, and CEC). Humid and dry forest areas presented a high diversity of AMF, and the soil properties were an important factor for the community composition of these fungi.

Communities of arbuscular mycorrhizal fungi in maize (Zea mays L.) crops along an edaphoclimatic gradient in Northeast Brazil

The objective of this study was to determine the species richness, diversity, and communities of arbuscular mycorrhizal fungi (AMF), based on the morphology of their spores, in maize plantations along an edaphoclimatic gradient going from a humid zone (original area of Atlantic rainforest), to a transition zone and a drier zone (original area of Caatinga), to increase the understanding of the ecology of AMF in tropical agroecosystems. We extracted glomerospores from soil samples from maize plantations in each mesoregion and analysed AMF propagules and community structure. A total of 57 AMF taxa were identified, of which two are new to science. The most probable number of AMF infective propagules did not differ among the three areas. A greater number of glomerospores was obtained from the transition site, whereas species richness for AMF differed between the high humidity and transition sites. The composition of AMF communities differed among sites, with edaphic attributes significantly associated with AMF community composition. The environmental conditions of each mesoregion contribute to the structural differences of AMF assemblages in soils cultivated by the same host plant (maize).