Mycorrhizal Fungal Communities Research Articles

Causal determinism by plant host identity in arbuscular mycorrhizal fungal community assembly

Abstract An assumption in ecology is that plant identity plays a central role in the assembly of root‐colonising arbuscular mycorrhizal (AM) fungal communities. While numerous correlational studies support this notion, with evidence of host selectivity among fungal taxa and host‐specific responses to different AM fungi, empirical demonstrations of host‐driven AM fungal community assembly remain surprisingly limited. We conducted a factorial experiment growing two globally significant crop species, wheat (Triticum aestivum) and sorghum (Sorghum bicolor), with a common pool of AM fungal species, or without AM fungi. We hypothesised strong differences in AM fungal community structure between the two species driven by strong habitat filtering. Plants were harvested at two time points in which we analysed the community structure of AM fungi in the roots, the phylogenetic diversity, and interactions with plant physiological responses. As we expected, there were distinct trajectories in both the composition and phylogenetic diversity of AM fungal communities between the two host plants through time. However, the effect of habitat filtering during community assembly differed between the two species. In sorghum roots, AM fungal communities exhibited increased richness and became more phylogenetically clustered over time. This shift suggests that community assembly was primarily driven by habitat filtering, or selectivity, imposed by the host which was accompanied by significant increases in plant mycorrhizal growth (from 11.83% to 43.67%) and phosphorus responses (from −0.6% to 43.3%). In contrast, AM fungal communities in wheat displayed little change in diversity, remained phylogenetically unstructured, and provided minimal benefits to the host, indicating a more stochastic assembly process with a stronger influence of competitive interactions. As the field looks to understand what determines the distribution of AM fungi and their community composition while simultaneously seeking to utilise AM fungi for ecosystem benefits, it is important to know the extent to which host identity can influence fungal assembly within plant roots. Our results provide empirical support of host‐determinism in AM fungal community assembly and suggest that this determinism is associated with the growth and nutrient benefits provided by the symbiosis to plants. Read the free Plain Language Summary for this article on the Journal blog.

Not only transitions in nutritional modes but also niche shifts facilitate mycorrhizal fungal specialization in Burmannia

Abstract Mycoheterotrophs are non‐photosynthetic plants that obtain all of their carbon requirements through parasitizing mycorrhizal fungi. They originated from the autotrophic ancestors and usually have more specific relationships with fungi than that of green plants, for reasons that are largely unknown. Determining the factors that lead to specificity in mycoheterotrophs could provide insights on the constraints to mycoheterotrophic evolution. Here we assess the fungal diversities in mycoheterotrophic plants and their co‐occurring plants to determine the roles of ecological factors on the specific fungal associations in mycoheterotrophic plants. We investigated mycorrhizal fungal communities in 16 populations of seven Burmannia species with different trophic modes and their co‐occurring plants using high‐throughput sequencing to assess the tripartite relationships of fungi, mycoheterotrophs and co‐occurring autotrophs. We found that mycoheterotrophic species have similar fungal richness to their chlorophyllous relatives, indicating that they are not associated with a reduced set of fungal partners. The preference of mycoheterotrophic species toward specialized fungal assemblages is consistent with the pattern found in the green autotrophic plants within forest habitats, suggesting a coupling of the fungal phylogenetic constraints between mycoheterotrophs and their co‐occurring autotrophs. We furthermore show that the turning to fungal communities having closer phylogenetic relationships during habitat shifts from open grasslands to shaded forests might provide the basis for the specialization of mycorrhizal associations in mycoheterotrophic species of Burmannia. Our findings suggest that fungal niche shifts may have promoted fungal partner changes and specialization in mycoheterotrophic plants. Our results provide new insights into the ecological factors leading to the specialized interactions between mycoheterotrophic plants and their fungal partners, expanding our understanding of the evolutionary trajectories followed by mycoheterotrophs. Read the free Plain Language Summary for this article on the Journal blog.

Soil amendments altered arbuscular mycorrhizal fungal communities in cadmium-contaminated vegetable fields.

Soil amendments, including various types of fertilizers, are often used to control the uptake of heavy metals such as cadmium in cropping fields. The influence of these amendments on other members of the agroecosystem, such as arbuscular mycorrhizal fungi (AMF), remains less well investigated. Here, we established an experiment with the application of woody peat organic fertilizer and phosphate rock powder to examine its effects on AMF communities in two cadmium-contaminated vegetable crop fields (cucumber and pepper). We found that the application of phosphate rock powder enhanced soil phosphorus content, while the application of woody peat organic fertilizer enhanced soil nitrogen content, but neither influenced AMF abundance. We also found little influence of either amendment on measures of AMF diversity, except in one case where the Shannon index of diversity was lower in pepper fields amended with phosphate rock powder. We did, however, find significant shifts in the community composition and relative abundances of AMF taxa in the two vegetable fields, primarily as a result of shifts in the soil pH and nitrogen content.

Increasing Phylogenetic Clustering of Arbuscular Mycorrhizal Fungal Communities in Roots Explains Enhanced Plant Growth and Phosphorus Uptake

Temporal variation during the assembly of arbuscular mycorrhizal (AM) fungal communities within plant roots have been posited as critical drivers of the plant-fungal symbiotic outcomes. However, functional implications of these dynamics for the host plant remain poorly understood. We conducted a controlled pot experiment with Sorghum bicolor to investigate how temporal shifts in AM fungal community composition and phylogenetic diversity influence plant growth and phosphorus responses to the symbiosis. We characterised the root-colonising AM fungal communities across three time points and explored their community assembly processes by analysing their phylogenetic diversity and employing joint species distribution modelling with the Hierarchical Modelling of Species Communities (HMSC) framework. We found strong AM fungal turnover through time with a high phylogenetic signal, indicating recruitment of phylogenetically clustered AM fungal species in the host. This temporal phylogenetic clustering of communities coincided with marked increases in plant biomass and phosphorus responses to the AM fungal symbiosis, suggesting that host selection for specific fungi may be a key determinant of these benefits.

Insight into the assembly process of angiosperms and arbuscular-mycorrhizal fungi in tropical wetland ecosystems

ABSTRACT Background The interaction between plants and mycorrhizal fungi is one of the most important and well-studied in ecology. However, the manner in which ecological communities of plants and arbuscular mycorrhizal (AM) fungi are structured by both deterministic and stochastic processes remains unclear. Aims To quantify the role of deterministic and stochastic assembly processes in both plant and arbuscular mycorrhizal (AM) fungal communities along with environmental filters in the assembly of communities in areas subject to flooding. Methods We studied phylogenetic relationships and diversity measures in plants and arbuscular mycorrhizal fungi in three tropical coastal wetland communities with contrasting landscapes and soil properties. Results We found that non-random processes were dominant in plant communities, while mycorrhizal communities appeared to be determined by stochastic processes. Clustering trends were predominant in plant communities in areas subject to flooding. Conclusion Environment filters and limiting similarity drive the plant community assembly, whereas ecological drift and/or dispersal limitations were determinants in the assembly of mycorrhizal communities. Environmental filters were found to be the main driver of plant community assembly in in areas subject to flooding.

Effects of direct and conventional planting systems on mycorrhizal activity in wheat grown in the Cerrado

Direct planting systems offer several benefits to the soil and plants, as reflected in soil organisms. The Arbuscular mycorrhizal fungi are extremely sensitive to environmental changes and can be used as indicators of soil quality. This study focused on the native diversity of mycorrhizae in the region. Thus, the objective of this work was to evaluate mycorrhizal colonization, spore density, soil glomalin content and species diversity in five wheat genotypes under direct and conventional planting systems. This work was carried out in the experimental area of Embrapa Cerrados, Planaltina, DF, Brazil. The rates of mycorrhizal colonization, spore density and easily extractable glomalin were evaluated, and species of arbuscular mycorrhizal fungi were identified in five wheat genotypes under direct and conventional planting. For all the genotypes under conventional planting, there was a decrease in mycorrhizal colonization, the number of spores in the rhizosphere and the amount of easily extractable glomalin. The composition of the arbuscular mycorrhizal fungal community differed among the wheat genotypes and management systems. The richness of morphospecies of AMF in the direct planting system was similar to that in the conventional system, with twelve species each, but the conventional system reduced root colonization and spore density. The most common species were A. scrobiculata, Si. tortuosum and G. macrocarpum, which were found in all the genotypes in both cultivation systems.

How important is important? A commentary on 'Temporal turnover of Ceratobasidiaceae orchid mycorrhizal fungal communities with ontogenetic and phenological development in Prasophyllum (Orchidaceae)'.

How important is important? A commentary on 'Temporal turnover of Ceratobasidiaceae orchid mycorrhizal fungal communities with ontogenetic and phenological development in Prasophyllum (Orchidaceae)'.

Mechanical mowing of semi‐natural grasslands compromises soil quality and survival of a conservation target plant species

Mowing is a crucial management strategy for conservation and restoration of semi‐natural grasslands. In the past decades, dominant mowing methods have changed from manual to mechanical, using heavy machines causing soil compaction. Whereas the negative effects of compaction are well understood in agriculture and forestry, they have received little attention so far in nature management. This study aims to investigate the effects of compaction on soil quality, arbuscular mycorrhizal fungal communities, and survival of a target plant species. We subjected seven grasslands to three contrasting mowing types: manual mowing with a brush cutter, softtrack mowing—designed to minimize soil compaction—and tractor mowing. We compared compaction, soil properties, and arbuscular mycorrhizal communities among the types. Additionally, we experimentally subjected intact grassland sods containing Devil's bit scabious (Succisa pratensis Moench), a target species of grassland conservation, to compaction levels corresponding to the three mowing types. Subsequently, we assessed plant survival. We found that soil compaction, soil nutrient availability, and toxic soil elements were significantly higher in the softtrack‐ and tractor‐mown parts of grassland sites compared to the manually mown parts. Also, the arbuscular mycorrhizal community composition differed significantly among mowing types, with the largest differences between “manual” and “tractor.” Succisa pratensis survival significantly decreased by 43 and 71% on the short term and by 71 and 86% on the longer term with increasing compaction. Consequently, mowing‐associated soil compaction compromises nature management targets via at least four mechanisms: nutrient enrichment, soil toxicity, changes in arbuscular mycorrhizal communities, and decreased survival of the target plant species.

Arbuscular mycorrhizal fungal spore communities and co-occurrence networks demonstrate host-specific variation throughout the growing season

Microbial community assembly involves a series of ecological filtering mechanisms that determine the composition of microbial communities. While the importance of both broad and local level factors on microbial communities has been reasonably well studied, this work often is limited to single observations and neglects to consider how communities change over time (i.e., seasonal variation). Because seasonal variation is an important determinant of community assembly and determines the relative importance of community assembly filters, this represents a key knowledge gap. Due to their close associations with seasonal variation in plant growth and fitness, arbuscular mycorrhizal (AM) fungi are useful groups for assessing the importance of seasonal dynamics in microbial community assembly. We tested how seasonal variation (spring vs. summer), plant life history stage (vegetative vs. flowering), and host plant species (Baptisia bracteata var. leucophaea & Andropogon gerardii) influenced AM fungal spore community assembly. AM fungal spore community temporal dynamics were closely linked to plant host species and life history stage. While AM fungal spore communities demonstrated strong turnover between the spring (e.g., higher sporulation) and late summer (e.g., higher diversity), the strength and direction of these changes was modified by host plant species. Here we demonstrate the importance of considering temporal variation in microbial community assembly, and also show how plant-microbe interactions can modify seasonal trends in microbial community dynamics.

Winter forage crops influence soil properties through establishing different arbuscular mycorrhizal fungi communities in paddy field

Winter planting is promising for improving the utilization rate of fallow paddy fields in southern China by establishing arbuscular mycorrhizal fungi (AMF) communities. However, the effects of different winter forage crops on AMF community construction remain unknown. The AMF community establishment of different winter planting forage crops were conducted in oat, rye, Chinese milk vetch, and ryegrass, with winter fallow as a control. The AMF colonization rate, soil AMF spore density, community structure and diversity, and soil physicochemical properties were determined. The results showed that the total nitrogen and available nitrogen in winter Chinese milk vetch were 11.11% and 16.92% higher than those in winter fallow (P < 0.05). After planting winter forage crops, the AMF spore density in winter oat, rye, Chinese milk vetch, and ryegrass soil were 127.90%, 64.37%, 59.91%, and 73.62% higher than that before planting, respectively (P < 0.05). Claroideoglomus was the dominant AMF genus in the soil of winter planting oat, rye, and ryegrass. The average membership function value of winter Chinese milk vetch was the highest, indicating that it had the best comprehensive effect on soil physicochemical properties, AMF community structure and diversity, and fresh forage yield. Winter forage crops could increase the spore pool of soil AMF and improve the soil AMF community structure and diversity. Winter Chinese milk vetch in paddy field had the best comprehensive effect on soil physicochemical properties and soil AMF community according to the comprehensive evaluation. These findings provide a theoretical basis for sustainable development and utilization of the southern rice paddy ecosystem.

Long-Term Manuring Enhanced Compositional Stability of Glomalin-Related Soil Proteins through Arbuscular Mycorrhizal Fungi Regulation

Glomalin-related soil proteins (GRSP) play a crucial role in strengthening soil structure and increasing carbon (C) storage. However, the chemical stability of GRSP and related arbuscular mycorrhizal fungi (AMF) community response to fertilization remains unclear. This study investigated C and nitrogen (N) contents, three-dimensional fluorescence characteristics in GRSP, and AMF properties based on a field experiment that was subjected to 29 years of various fertilizations. The experiment included treatments with no fertilizer (CK), chemical fertilizer (NPK), manure (M), and manure combined with NPK (NPKM) treatments. Results showed that GRSP contained 37–49% C and 6–9% N, respectively. Compared with CK and NPK, the C and N proportions in GRSP significantly increased under M and NPKM. Using the parallel factor model, four fluorescent components of GRSP were identified: one fulvic acid-like component (C2), one tyrosine-like component (C4), and two humic acid-like components (C1, C3). Under M and NPKM, the fluorescent intensity of C2 and C4 decreased, while the humification index (HIX) increased relative to CK and NPK, indicating that organic fertilization could enhance the stability of GRSP. The C and N proportion in GRSP positively associated with soil organic C (SOC), total N (TN), available phosphorus (AP), AMF biomass, and diversity, while C2 and C4 showed negative associations. Structural equation modeling further revealed that manure-induced changes in pH, SOC, TN, and AP increased AMF biomass and diversity, thereby altering GRSP composition and stability. This study provides valuable insights into the compositional traits of GRSP, contributing to sustainable soil management and C sequestration in agroecosystems.

Diversification of crops and intensification of canola impact the diversity, community structure, and productivity in successive crop systems: A study on arbuscular mycorrhizal fungal communities in roots and rhizosphere

The widespread cultivation of canola, conventionally still considered a non-host plant for AM fungi, coupled with its increasing frequency in crop rotations, raises concerns about its impacts on soil microbial diversity and overall crop productivity. The main objective of this study is to assess the influence of different crop succession systems, incorporating canola, on AM fungal diversity and community structure in both the roots and in the rhizosphere, as well as on productivity of each crop present within the succession. Doubling the frequency of canola occurrence in a 4-year crop succession did not reduce the productivity of the other crops in the succession, nor did it result in a decrease in AM fungal biodiversity in the roots or rhizosphere of these crops. Interestingly, the diversity of AM fungi was higher in canola roots compared to wheat roots, indicating that canola might serve as a rudimentary host of AM fungi. The succession systems did, however, alter the AM fungal community structure in both roots and rhizosphere environments, exhibiting positive or negative correlations with crop productivity. This suggests that a simple modification of the cropping system could potentially be employed to manipulate root or rhizosphere microbiomes. Results of this study add to the growing body of evidences that plants that were thought to be non-AM fungi host, such as plants from the Brassicaceae family, could in fact interact with AM fungi.

Root Endophyte-Manipulated Alteration in Rhizodeposits Stimulates Claroideoglomus in the Rhizosphere to Enhance Drought Resistance in Peanut.

Drought dramatically affects plant growth and yield. A previous study indicated that endophytic fungus Phomopsis liquidambaris can improve the drought resistance of peanuts, which is related with the root arbuscular mycorrhizal fungi (AMF) community; however, how root endophytes mediate AMF assembly to affect plant drought resistance remains unclear. Here, we explored the mechanism by which endophytic fungus recruits AMF symbiotic partners via rhizodeposits to improve host drought resistance. The results showed that Ph. liquidambaris enhanced peanut drought resistance by enriching the AMF genus Claroideoglomus of the rhizosphere. Furthermore, metabolomic analysis indicated that Ph. liquidambaris significantly promoted isoformononetin and salicylic acid (SA) synthesis in rhizodeposits, which were correlated with the increase in Claroideoglomus abundance following Ph. liquidambaris inoculation. Coinoculation experiments confirmed that isoformononetin and SA could enrich Claroideoglomus etunicatum in the rhizosphere, thereby improving the drought resistance. This study highlights the crucial role of fungal consortia in plant stress resistance.

Water availability and accessions of Passiflora cincinnata Mast. can shape the communities of arbuscular mycorrhizal fungi

Understanding how water availability affects different caatinga passionfruit accessions (Passiflora cincinnata Mast.) and their drought tolerance is crucial for successful cultivation in semi-arid environments. Additionally, assessing the impact of this stress on arbuscular mycorrhizal fungi (AMF) communities' structure and dynamics is also essential. A greenhouse experiment was conducted with the purpose of identifying tolerant and sensitive P. cincinnata accessions under drought stress and how the water availability would affect AMF communities, which were taxonomically identified based on morphological characters. Results show that water availability influenced height, stem diameter, total chlorophyll, dry and fresh shoot biomass, fresh root biomass, leaf area, number of leaves and tendrils, and root/shoot ratio of accessions of P. cincinnata. However, water availability did not influence root dry biomass, only the identity of P. cincinnata accessions differed from each other. In the PCA-based ranking, based on the morpho-descriptors traits, and on the indices of drought stress tolerance, accessions 01 and 48 were considered tolerant and sensitive to drought, respectively. The abundance of glomerospores and the AMF richness are not influenced by the factors studied, but water availability has increased the frequency of mycorrhizal colonization, diversity, and evenness of AMF species, in addition to reducing its dominance. AMF communities’ composition was modulated by P. cincinnata accessions and by water availability. Utilizing morpho-agronomic traits, it becomes feasible to differentiate P. cincinnata accessions exhibiting tolerance and sensitivity to drought stress. Particular emphasis is placed on fresh and dry shoot biomass, leaf area, and height, each contributing approximately 12% to these outcomes. Changes on the composition of AMF communities after imposition of water deficit suggest that some AMF species may show some drought tolerance and that preferences for P. cincinnata genotypes may exist.

No-tillage facilitates soil organic carbon sequestration by enhancing arbuscular mycorrhizal fungi-related soil proteins accumulation and aggregation

No-tillage is known to optimize soil structure and enhance soil organic carbon (SOC) stocks in cropland. However, the exact mechanisms driving the accumulation of SOC are still unclear, especially concerning the regulation of arbuscular mycorrhizal fungi (AMF) communities and diversity in SOC sequestration. Here, this study aims to elucidate the intricate relationship between AMF community, glomalin-related soil proteins (GRSP), and SOC within bulk soil and aggregates across four tillage treatments (i.e. FA, fallow; RT, rotary tillage; DT, deep tillage; NT, no-tillage) based on a 7-year tillage experiment. Results showed that the contents of SOC and GRSP were significantly higher by 1.14–1.46 mg/g and 0.43–0.72 mg/g in the bulk soil under NT relative to RT and DT, respectively. The contribution of GRSP-C to SOC under NT was also higher than RT and DT, especially in > 53 μm particle size. Additionally, NT increased AMF diversity and the abundance of glomerales and diversisporales, all showing a strong positive correlation with GRSP (p < 0.05), indicating their potential regulatory role in GRSP production. The positive correlations between GRSP and the mass percentage of the > 53 μm particle size fraction (R2 = 0.74; p < 0.01) and MWD (R2 = 0.63; p < 0.01) suggested that no-tillage may drive large aggregates (>53 μm) formation and enhance aggregate stability through GRSP levels. Overall, increased AMF diversity and keystone taxa abundance at the order level via no-tillage promoted SOC accumulation through the production of GRSP and the protection of large aggregates. This study highlights that no-tillage is an effective and sustainable soil management strategy for enhancing soil quality in agricultural ecosystems.

Unveiling the influence of seawater intrusion and vegetation type on coastal arbuscular mycorrhizal fungal communities in China

AbstractContinuously rising sea levels pose severe threats to the diversity and stability of coastal ecosystems. However, the responses of endospheric and rhizospheric arbuscular mycorrhizal (AM) fungal communities to accelerated seawater intrusion and changing vegetation types unfortunately remains unknown. Such insights will assist in revealing the structure of AM fungi across different tidal zones, enabling the development of effective measures to conserve biodiversity. Here, we investigated changes in endospheric and rhizospheric AM fungal communities associated with four types of coastal vegetation in Dafeng City, Jiangsu Province, China, in response to sea level variations by analyzing their characteristics and connections to selected environmental factors. It was found that the AM fungal communities of coastal vegetation differed significantly in their compositions, diversity, and stability (the resilience or resistance of a community). Despite the responses of endospheric and rhizospheric AM fungi to soil environmental factors, the soil electrical conductivity, cation exchange content, and inorganic carbon were identified as core elements that influenced the characteristics of AM fungal communities between different coastal vegetation species. Lastly, the major endospheric and rhizospheric species of AM fungi were important predictors that explained much of the variation in the soil environment. Consequently, the dynamics of AM fungal communities were correlated with the plant–soil system under different conditions. Apart from the coastal vegetation species, the characteristics of AM fungal communities can also be driven by high salinity and the inorganic carbon content induced by the intrusion of seawater.

Cover crop mixtures do not assemble markedly distinct soil microbiotas as compared to monocultures in a multilocation field experiment

Cover crops are used in cropping systems to enhance ecosystem services, such as soil resilience to erosion or microbial activity. Different cover crops are selected to steer specific processes, but whether cover crop mixtures have an added value over monocultures remains debated. Here, we investigated if cover crop mixtures accumulate soil microbiotas distinct from those of monocultures, potentially leading to more varied microbially-driven soil functions. We performed a field experiment at three locations in the Netherlands, each including nine cover crop monocultures, five- and eight-species mixtures, and a fallow control. After three months, we measured cover crop biomass and profiled soil bacterial, fungal, and arbuscular mycorrhizal fungal communities via amplicon sequencing. The different crop monocultures produced similar biomass across all three locations, and mixtures had average productivity compared to monocultures. The diversity and community structure of soil microbial communities was primarily determined by the geographical location, and then by cover crop treatment at each location. Although the cover crop species affected the soil microbiome differently, cover crop mixtures did neither increase microbial diversity nor the overall community differentiation compared to monocultures. Our results suggest that mixing cover crop species does not significantly influence microbially-driven soil functions, at least in short-term crop rotations.

Grazing exclusion enriches arbuscular mycorrhizal fungal communities and improves soil organic carbon sequestration in the alpine steppe of northern Tibet

Fencing for grazing exclusion is regarded as a traditional and effective method for the natural restoration of degraded alpine steppe, and it effectively promotes plant growth and enhances soil carbon stocks. Arbuscular mycorrhizal fungi (AMF) are essential microorganisms in grassland that play a major role in plant-derived C translocation into the soil. However, the effects of fencing on AMF communities and their contributions to soil carbon sequestration are still unclear. In this study, alpine steppe areas with three different fencing durations (free grazing, medium-term fencing for 5-6 years and long-term fencing for more than 10 years) in the northern Tibetan Plateau were selected to explore the effects of grazing exclusion on AMF communities and their roles in soil carbon sequestration. The results showed that medium- and long-term fencing significantly increased both plant aboveground biomass and soil organic carbon (SOC) content. The AMF community composition varied significantly during different fencing durations, with a dramatic increase in the relative abundance of Glomus but a significant reduction in the relative abundance of Diversispora with longer fencing time. Medium-term fencing significantly increased AMF richness and the Shannon-Wiener index. Meanwhile, fencing significantly increased hyphal length density (HLD), glomalin-related soil protein (GRSP) and the proportion of macroaggregates (250-2,000 μm), all of which contribute positively to SOC. Structural equation modeling revealed that fencing time positively influenced HLD and the AMF community composition, subsequently affecting T-GRSP, which was tightly correlated with SOC. Our findings suggest the potentially important contribution of AMF to SOC sequestration, so more attention should be paid to AMF during alpine steppe fencing, particularly for enhancing the efficiency of degraded grassland restoration efforts.

Diversified Cover Crops and No-Till Enhanced Soil Total Nitrogen and Arbuscular Mycorrhizal Fungi Diversity: A Case Study from the Karst Area of Southwest China

The deteriorating soil health under continuous monoculture is commonly found across various cropping systems. This study evaluated the effects of different tillage practices (conventional tillage and no till) and species mixtures (legumes and grasses) on arbuscular mycorrhizal fungi (AMF) community properties, soil nutrients, and enzyme activity in a 3-year experiment. Compared with traditional tillage, the number of AMF species under no-till conditions was increased, with the Glomus group being dominant. Under different tillage conditions, TN (total N) and AN (available N) contents under no till were significantly higher than those under conventional tillage, while no significant differences among other nutrients were found. The activities of soil acid phosphatase (S-ACP), soil dehydrogenase (S-DHA), and soil sucrose (S-SC) under conventional tillage were significantly higher than those under no till, and the cover crop mixtures also had an exclusive advantage in yield. Soil organic matter (SOM) indicated a significant negative correlation with glomalin-related soil protein (GRSP). The increase in diversity associated with the AMF species community was strongly correlated with the increase in three enzyme activities, and AN was negatively correlated with all species. Tillage did not significantly change soil chemistry, except for AN, and the high concentration of AN led to a decrease in AMF species. The results of this study showed that no till was an effective measure for enriching soil micro-organism population. Additionally, soil AMF diversity was improved by cover crop mixtures, and microbial diversity was higher than that under monoculture cover crops. Different AMF groups responded differently to tillage and cover crop mixtures. Across all mixtures, the combination of hairy vetch (Vicia villosa R.) and ryegrass (Lolium perenne L.) performed the best.

Bacterial community in the buckwheat rhizosphere responds more sensitively to single microplastics in lead-contaminated soil compared to the arbuscular mycorrhizal fungi community

Soil pollution by microplastics (MPs), defined as plastic particles <5 mm, and heavy metals is a significant environmental issue. However, studies on the co-contamination effects of MPs and heavy metals on buckwheat rhizosphere microorganisms, especially on the arbuscular mycorrhizal fungi (AMF) community, are limited. We introduced low (0.01 g kg−1) and high doses of lead (Pb) (2 g kg−1) along with polyethylene (PE) and polylactic acid (PLA) MPs, both individually and in combination, into soil and assessed soil properties, buckwheat growth, and rhizosphere bacterial and AMF communities in a 40-day pot experiment. Notable alterations were observed in soil properties such as pH, alkaline hydrolyzable nitrogen (AN), and the available Pb (APb). High-dose Pb combined with PLA-MPs hindered buckwheat growth. Compared to the control, bacterial Chao1 richness and Shannon diversity were lower in the high dose Pb with PLA treatment, and differentially abundant bacteria were mainly detected in the high Pb dose treatments. Variations in bacterial communities correlated with APb, pH and AN. Overall, the AMF community composition remained largely consistent across all treatments. This phenomenon may be due to fungi having lower nutritional demands than bacteria. Stochastic processes played a relatively important role in the assembly of both bacterial and AMF communities. In summary, MPs appeared to amplify both the positive and negative effects of high Pb doses on the buckwheat rhizosphere bacteria.