Arbuscular Mycorrhizal Communities Research Articles

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.

The rootstock modifies the arbuscular mycorrhizal community of the root system, while the influence of the scion is limited in grapevines.

Understanding the effects of grapevine rootstock and scion genotypes on arbuscular mycorrhizal fungi (AMF), as well as the roles of these fungi in plant development, could provide new avenues for adapting viticulture to climate change and reducing agrochemical inputs. The root colonization of 10 rootstock/scion combinations was studied using microscopy and metabarcoding approaches and linked to plant development phenotypes. The AMF communities were analysed using 18S rRNA gene sequencing. The 28S rRNA gene was also sequenced for some combinations to evaluate whether the method changed the results. Root colonization indexes measured by microscopy were not significantly different between genotypes. Metabarcoding analyses showed an effect of the rootstock genotype on the β-diversity and the enrichment of several taxa with both target genes, as well as an effect on the Chao1 index with the 18S rRNA gene. We confirm that rootstocks recruit different AMF communities when subjected to the same pedoclimatic conditions, while the scion has little or no effect. Significant correlations were observed between AMF community composition and grapevine development, suggesting that AMF have a positive effect on plant growth. Given these results, it will be important to define consensus methods for studying the role of these beneficial micro-organisms in vineyards.

Arbuscular mycorrhizal communities respond to nutrient enrichment and plant invasion in phosphorus‐limited eucalypt woodlands

Abstract Arbuscular mycorrhizal fungi (AMF) facilitate ecosystem functioning through provision of plant hosts with phosphorus (P), especially where soil P is limiting. Changes in soil nutrient regimes are expected to impact AMF, but the direction of the impact may depend on context. We predicted that nitrogen (N)‐only enrichment promotes plant invasions and exacerbates their P limitation, increasing the utility of AMF and promoting AMF diversity. We expected that enrichment with N, P and other nutrients similarly promotes plant invasions, but decreases the benefit and diversity of AMF because P is readily available for both native and exotic plants. We tested these hypotheses in eucalypt woodlands of south‐western Australia, that occur on soils naturally low in P. We evaluated AMF communities within three modified ground‐layer states representing different types of nutrient enrichment and associated plant invasions. We compared these modified states to near‐natural reference woodlands. AMF richness varied across ground‐layer states. The moderately invaded/N‐enriched state showed the highest AMF richness, while the highly invaded/NP‐enriched state showed the lowest AMF richness. The reference state and the weakly invaded/enriched state were intermediate. AMF richness and colonisation were higher in roots of exotic than native plant species. AMF community composition differed among ground‐layer states, with the highly invaded/NP‐enriched state being most distinct. Distinctions among states were often driven by family‐level patterns. Reference and moderately invaded/N‐enriched states each supported distinct groups of zero‐radius operational taxonomic units (zOTUs) in Acaulosporaceae, Gigasporaceae and Glomeraceae, whereas Gigasporaceae and Glomeraceae were nearly absent from the highly invaded/NP‐enriched state. Further, Diversisporaceae and Glomeraceae were most diverse in the moderately invaded/N‐enriched state. Synthesis. Both the nature of soil nutrient enrichment and plant provenance matter for AMF. N‐only enrichment of low‐P soils increased AMF richness, likely due to the introduction of AMF‐dependent exotic plant species and exacerbation of their P limitation. In contrast, multi‐nutrient enrichment, decreased AMF richness potentially due to a decrease in host dependence on AMF, regardless of host provenance. The changes in AMF community composition with nutrient enrichment and plant invasion warrant further research into predicting the functional implications of these changes.

Arbuscular mycorrhizal fungal diversity and potential association networks among African tropical forest trees.

Tropical forests represent one of the most diverse and productive ecosystems on Earth. High productivity is sustained by efficient and rapid cycling of nutrients, which is in large part made possible by symbiotic associations between plants and mycorrhizal fungi. In these associations, an individual plant typically associates simultaneously with multiple fungi and the fungi associate with multiple plants, creating complex networks among fungi and plants. However, there are few studies that have investigated mycorrhizal fungal composition and diversity in tropical forest trees, particularly in Africa, or that assessed the structure of the network of associations among fungi and trees. In this study, we collected root and soil samples from Ise Forest Reserve (Southwest Nigeria) and used a metabarcoding approach to identify the dominant arbuscular mycorrhizal (AM) fungal taxa in the soil and associating with ten co-occurring tree species to assess variation in AM communities. Network analysis was used to elucidate the architecture of the network of associations between fungi and tree species. A total of 194 Operational Taxonomic Units (OTUs) belonging to six AM fungal families were identified, with 68% of all OTUs belonging to Glomeraceae. While AM fungal diversity did not differ among tree species, AM fungal community composition did. Network analyses showed that the network of associations was not significantly nested and showed a relatively low level of specialization (H2 = 0.43) and modularity (M = 0.44). We conclude that, although there were some differences in AM fungal community composition, the studied tree species associate with a large number of AM fungi. Similarly, most AM fungi had great host breadth and were detected in most tree species, thereby potentially working as interaction network hubs.

Plant genotype and inoculation with indigenous arbuscular mycorrhizal (AM) fungi modulate wheat productivity and quality of processed products through changes in the frequency of root AM fungal taxa

ContextArbuscular mycorrhizal fungi (AMF) have been extensively applied as biofertilizers in wheat to promote crop productivity. However, variability in AM root colonization, grain yield, and nutrients was observed among wheat genotypes and according to AM genotype and environment. ObjectivesWe hypothesized that wheat response to AM inoculation is more affected by genotype than environment; the response is driven by increases in AM abundance and community structure changes, and not by modification of composition. MethodsWe inoculated an indigenous AM consortium on four old genotypes (Bianco Nostrale, Andriolo, Abbondanza, Sieve) and one modern variety (Bologna) of bread wheat for two years. The effect was evaluated by assessing grain yield, nutrients, and quality of processed products (flour and breadsticks), while the AM abundance and the community composition and structure in roots were characterized, at two plant growth stages, using morphological and molecular tools. ResultsThe functional traits of AMF and plant were better explained by inoculation than by genotype or environment (33 %, 17 %, 4 % of total explained variance), although significant interactions environment x genotype and genotype x inoculation were highlighted. Consistent increases in AM abundance in Sieve and Bologna were associated with positive changes in grain yield and nutrients, supporting the good responsiveness of these genotypes with inoculated AMF, while the plant response of other genotypes was shaped by air temperature and rainfall. However, we did not find significant correlations between changes in AM colonization and mycorrhizal response ratio, with the exception of P and K. After inoculation, AM community composition was similar in all wheat genotypes, but the structure greatly differed among genotypes in interaction with inoculation and plant growth stage. These changes were significantly related to wheat productivity. A Septoglomus taxon, present in the inoculum, was the best predictor of wheat performance. The characterization of the community structure at early crop development and maturity allowed the identification of fast and latest active AM colonizers. Our results showed for the first time that AM inoculation affect the rheological parameters and nutraceuticals of processed products, although the response was modulated by genotype. ConclusionsThe selection of responsive wheat genotypes is fundamental for the positive outcome of inoculation. The positive effects on wheat productivity and field persistence of the inoculated AMF support the use of indigenous consortia that have low impacts on resident AMF. SignificanceOur findings advance the understanding of the facilitative mechanisms that underlie compatibility between AMF and wheat genotypes.

Common soil history is more important than plant history for arbuscular mycorrhizal community assembly in an experimental grassland diversity gradient

The relationship between biodiversity and ecosystem functioning strengthens with ecosystem age. However, the interplay between the plant diversity - ecosystem functioning relationship and Glomeromycotinian arbuscular mycorrhizal fungi (AMF) community assembly has not yet been scrutinized in this context, despite AMF’s role in plant survival and niche exploration. We study the development of AMF communities by disentangling soil- and plant-driven effects from calendar year effects. Within a long-term grassland biodiversity experiment, the pre-existing plant communities of varying plant diversity were re-established as split plots with combinations of common plant and soil histories: split plots with neither common plant nor soil history, with only soil but no plant history, and with both common plant and soil history. We found that bulk soil AMF communities were primarily shaped by common soil history, and additional common plant history had little effect. Further, the steepness of AMF diversity and plant diversity relationship did not strengthen over time, but AMF community evenness increased with common history. Specialisation of AMF towards plant species was low throughout, giving no indication of AMF communities specialising or diversifying over time. The potential of bulk soil AMF as mediators of variation in plant and microbial biomass over time and hence as drivers of biodiversity and ecosystem relationships was low. Our results suggest that soil processes may be key for the build-up of plant community-specific mycorrhizal communities with likely feedback effects on ecosystem productivity, but the plant-available mycorrhizal pool in bulk soil itself does not explain the strengthening of biodiversity and ecosystem relationships over time.

Foliar herbivory‐enhanced mycorrhization is associated with increased levels of lipids in root and root exudates

Abstract Insect herbivory can affect interactions between plants and arbuscular mycorrhizal (AM) fungi through herbivore‐modified root carbon pools, while the specific metabolic changes underlying fungal responses to herbivory are poorly understood. Here we explored the impacts of foliar herbivory and mechanical wounding on AM colonisation and AM community composition of common ragweed (Ambrosia artemisiifolia) and the role of root metabolites in mediating these effects. Foliar insect herbivory enhanced AM colonisation, whereas mechanical wounding only enhanced AM colonisation in combination with application of caterpillar oral secretions. Meanwhile, the relative abundance of Glomus species was increased in root endosphere, rhizoplane and rhizosphere soils after foliar herbivory. Foliar herbivory also increased the concentrations of fatty acids in roots but decreased phenolics, and their concentrations were significantly correlated with AM colonisation. Addition of exudates from plants exposed to herbivory resulted in increases in AM colonisation of plants without herbivory. Moreover, widely targeted metabolomic analyses revealed that foliar herbivory enhanced the relative abundance of lipids and decreased phenols in root exudates. Synthesis. We show that plants can enhance their associations with arbuscular mycorrhizal (AM) fungi when subject to above‐ground herbivory, possibly mediated by herbivore‐induced increases in the levels of root lipids. Our findings highlight the role of root lipids in above‐below‐ground biological interactions, providing novel insights into plant‐AM fungi integrative responses to biotic stresses.

Influence of plant species, mycorrhizal inoculant, and soil phosphorus level on arbuscular mycorrhizal communities in onion and carrot roots.

Arbuscular mycorrhizal fungi (AMF) are ancient and ecologically important symbionts that colonize plant roots. These symbionts assist in the uptake of water and nutrients, particularly phosphorus, from the soil. This important role has led to the development of AMF inoculants for use as biofertilizers in agriculture. Commercial mycorrhizal inoculants are increasingly popular to produce onion and carrot, but their specific effects on native mycorrhizal communities under field conditions are not known. Furthermore, adequate availability of nutrients in soils, specifically phosphorus, can reduce the diversity and abundance of AMF communities in the roots. The type of crop grown can also influence the composition of AMF communities colonizing the plant roots. This study aimed to investigate how AMF inoculants, soil phosphorus levels, and plant species influence the diversity of AMF communities that colonize the roots of onion and carrot plants. Field trials were conducted on high organic matter (muck) soil in the Holland Marsh, Ontario, Canada. The treatments included AMF-coated seeds (three to five propagules of Rhizophagus irregularis per seed) and non-treated onion and carrot seeds grown in soil with low (~46 ppm) and high (~78 ppm) phosphorus levels. The mycorrhizal communities colonizing the onion and carrot roots were identified by Illumina sequencing. Five genera, Diversispora, Claroideoglomus, Funneliformis, Rhizophagus, and Glomus, were identified in roots of both plant species. AMF communities colonizing carrot roots were more diverse and richer than those colonizing onion roots. Diversispora and Funneliformis had a 1.3-fold and 2.9-fold greater abundance, respectively, in onion roots compared to carrots. Claroideoglomus was 1.4-fold more abundant in carrot roots than in onions. Inoculation with R. irregularis increased the abundance and richness of Rhizophagus in AMF communities of onion roots but not in carrot roots. The soil phosphorus level had no effect on the richness and diversity of AMF in the roots of either crop. In summary, AMF inoculant and soil phosphorus levels influenced the composition of AMF communities colonizing the roots of onion and carrot plants, but the effects varied between plant species.

Ecotype and fungal endophyte status differentially affect soil arbuscular mycorrhizal community of the native grass Bromus auleticus

In wild native grasses, the colonization of arbuscular mycorrhizal fungi (AMF) is higher in Epichloë-infected plants (E+) compared to Epichloë-free plants (E−). To explore the correlation between the host ecotype, Epichloë association, and the soil AMF community, a common garden experiment was conducted. To achieve this, the soil AMF community of two Bromus auleticus ecotypes, El Palmar (EP) and La Pampa (LP), with either E+ or E−endophyte status, was analyzed using high throughput sequencing. The total mycorrhizal colonization of E+ plants from both EP and LP ecotypes showed significantly higher values (178.68% and 132.34% respectively) compared to E−plants, regardless of the ecotype. Alpha and Beta diversity analysis revealed significant differences in AMF richness and composition between the El Palmar (EP) and La Pampa (LP) ecotypes. However, no differences were observed in the soil AMF communities between E+ and E−plants. In conclusion, this study demonstrates that Epichloë symbiosis and host ecotype have distinct effects on various aspects of the AMF-Bromus auleticus association.

Molecular characterization of arbuscular mycorrhizal communities associated with Lathyrus cicera L. grown in northern Tunisia soils

Molecular characterization of arbuscular mycorrhizal communities associated with Lathyrus cicera L. grown in northern Tunisia soils

Beta Diversity of Arbuscular Mycorrhizal Communities Increases in Time after Crop Establishment of Peruvian Sacha Inchi (Plukenetia volubilis).

(1) Background: Beta diversity, i.e., the variance in species compositions across communities, has been pointed out as a main factor for explaining ecosystem functioning. However, few studies have directly tested the effect of crop establishment on beta diversity. We studied beta diversity patterns of arbuscular mycorrhizal (AM) fungal communities associated to sacha inchi (Plukenetia volubilis) after crop establishment. (2) Methods: We molecularly characterized the AM fungal communities associated to roots of sacha inchi in plots after different times of crop establishment, from less than one year to older than three. We analyzed the patterns of alpha, beta, and phylogenetic diversity, and the sources of variation of AM fungal community composition. (3) Results: Beta diversity increased in the older plots, but no temporal effect in alpha or phylogenetic diversity was found. The AM fungal community composition was driven by environmental factors (altitude and soil conditions). A part of this variation could be attributed to differences between sampled locations (expressed as geographic coordinates). Crop age, in turn, affected the composition with no interactions with the environmental conditions or spatial location. (4) Conclusions: These results point out towards a certain recovery of the soil microbiota after sacha inchi establishment. This fact could be attributed to the low-impact management associated to this tropical crop.

Assessment of the potential of Vachellia seyal and Prosopis chilensis for the reclamation of saline soil lands in the peanut basin production of Senegal.

Soil properties and microbial activities are indicators that shape plant communities and evolution. We aimed to determine the interdependency between trees, belowground herbaceous plants, soil characteristics, and arbuscular mycorrhizal communities. Vachellia seyal and Prosopis chilensis and their associated herb layers were targeted. Soils sampled beneath the trees and outside the canopies were subjected to physicochemical and microbial characterization. Randomly collected living roots of trees and dominant herbs were checked for arbuscular mycorrhizal colonization. A tree seedlings nursery was conducted using black bags filled with the following substrates: natural soil 100%, soil mixed with leaf tree plants (LTPs) as organic matter at 10%, soil mixed with LTP at 20%, soil mixed with LTP at 30%, and soil mixed with LTP at 50%. As a result, the presence of trees improves both herb richness and diversity. Soil mycorrhizal inoculum potentials are higher beneath V. seyal than P. chilensis and decreased significantly with increasing distance from trees. The soil MIP decreased with increasing organic matter content for both tree species but was more pronounced for P. chilensis. Soil salinity is lower beneath V. seyal and higher under P. chilensis and outside the canopies. Soil fertility parameters such as carbon, nitrogen, and available phosphorus are higher beneath the trees and then decreased as the distance to the trees increases. We conclude that microbial communities, soil properties, and herb richness and diversity increased beneath the trees but decreased with increasing distance from the trees. This effect is tree species-dependent as P. chilensis increased soil salinity and decreased the belowground density of herbs.

Soil sodicity affected the arbuscular mycorrhizal community and its interactions with bacteria in the Western Songnen Plain

Soil sodicity affects plant growth and is a crucial factor degrading soil fertility and threatening grain yield worldwide. AM fungi form mutualistic symbiosis with plant roots and alleviate salt stress for the host plant. Therefore, understanding their distribution pattern and interactions with bacteria in natural saline-sodic soils would be essential to improve plant growth. Therefore, we examined AM fungal community and co-occurrence with soil bacteria across a wide sodicity gradient in the Western Songnen Plain. AM fungal traits, including root colonization and ERH (extraradical hyphal) density, showed negative correlations with soil sodicity, while spore density did not show correlation with soil sodicity. In total, 188 AM fungal OTUs were annotated at 97 % identity across 108 soil samples. Soil sodicity decreased AM fungal alpha-diversity and exerted strong influence on their community composition. Rare AM fungi were more sensitive to sodicity than abundant AM fungi, as confirmed by their decrease with the increasing soil sodicity and almost all rare AM fungi belonging to z- OTUs. Abundant rather than rare AM fungi contributed greatly to soil nutrient availability as shown by conducting a random forest analysis. Network analysis revealed a less connected AM fungi-bacteria co-occurrence network in moderately and extremely saline-sodic soils. Further analysis indicated that some bacteria that positively correlated with AM fungi indeed exhibited positive correlations with AM fungal hyphal and spore density. Overall, our results provide evidence that AM fungal community was greatly shaped by soil sodicity in the Songnen Plain, and provides an alternative way to identify positive AM-bacteria interactions in saline-sodic environments.

Drought rearranges preferential carbon allocation to arbuscular mycorrhizal community members co-inhabiting roots of Medicago truncatula

Arbuscular mycorrhizal (AM) fungi establish symbiosis with majority of plant species, supporting their abiotic and biotic stress tolerances, and receiving reduced carbon in return. However, how and why plants control the composition of their associated mycorrhizal communities remains largely unknown. Our aim was to analyze the consequences of abrupt changes in environmental conditions such as light intensity or water supply on carbon allocation from plant (Medicago truncatula) to different AM fungal species coexisting in plant roots, employing 13C labeling and tracing. Significant differences were detected in the composition of synthetic communities of AM fungi just ten days after the environmental change induction. Under simulated drought, plants preferentially allocated their carbon to Funneliformis mosseae to the detriment of Claroideoglomus claroideum. Compared to drought, shading did not lead to a significant rearrangement of carbon fluxes from plants to the different AM fungi. Our observations strongly suggest that plants actively promote, through preferential allocation of their carbon, specific AM fungal symbionts in their roots depending on environmental conditions. Yet, it still needs to be elucidated which fungal traits are playing a role in this process, how are the different symbionts recognized, and which molecular mechanisms are involved in such preferential carbon routing.

Effect of Defoliation Frequency on Rytidosperma Virescens Plants and Arbuscular Mycorrhizal Fungi Colonization

Rangelands provide different ecosystem services to satisfy human needs. Although grazing management in southern Patagonia is mostly characterized by extensive continuous grazing, rotational grazing management may improve plant productivity and its associated microbiome. Arbuscular mycorrhizal (AM) symbioses play an important role in the functioning of arid rangelands. However, in most arid and semiarid grasslands, little is known about the environment-plant-symbiont interaction under different defoliation frequencies and contrasting growth conditions. In this context, the objective of the present study was to evaluate the response of Rytidosperma virescens native grass and the associated AM fungi under different defoliation frequency treatments (plants undefoliated, two clippings with 50-d intervals between defoliations, four clippings with 30-d intervals, and six clippings with 21-d intervals) and two growth conditions (field and greenhouse) in a 150-d experiment. Defoliation frequency with 21-d clipping intervals negatively affected plants and AM colonization. We found a negative linear relationship between AM colonization and removal of aboveground biomass and a positive relationship with root biomass and leaf area of R. virescens plants. We determined that the appropriate recovery period for rotational grazing systems should be at least 50 d (threshold) to optimize forage production and AM symbiosis during spring-summer seasons. Sustainable grazing management practices should be designed to improve or restore AM communities to maintain positive feedback with plant development.

Cover crop selection affects maize susceptibility to the fungal pathogen Fusarium verticillioides

In this study, we show the impact of cover crop legacy in soil towards susceptibility of next generation maize to the fungal pathogen Fusarium verticillioides. The use of different plant species as cover crops in organic cropping systems has been shown to provide several ecosystem services. The direct benefits of using leguminous cover crops such as pea or mycorrhizal species such as cereal rye or oats for soil fertility and cash crop yield are well known. However, the impacts of different cover crop species on subsequent cash crop pest suppression is rarely accounted for in agricultural management. Legacy of cover crop species are of importance considering recent findings that plants promoting arbuscular mycorrhizal communities, such as cereal rye and oats as cover crops, can provide increased benefits to successive maize crops against insect pests. In this study, we test whether such benefits might also include resistance against pathogens. We examined progression of rot lesions in ear, stalk and seedling blight by Fusarium verticillioides in maize plants that were grown in soil with a cover crop monoculture history of either winter pea, triticale or radish. This study shows for the first time that soil legacy of mycorrhizal monocot triticale as a cover crop renders maize plants more susceptible to ear rot and seedling blight by Fusarium verticillioides as compared to a soil legacy of radish. This suggests that although soil legacy of radish may be detrimental to management of insects, it is effective in suppressing progression of Fusarium verticillioides in maize. This work demonstrates the significance of cover crop selection to manage fungal pathogens such as Fusarium verticillioides, it further suggests trade-offs in plant resistance to various pests’ taxa at the cover crop species level.

Mycorrhizal Fungi Associated With Juniper and Oak Seedlings Along a Disturbance Gradient in Central Mexico

Competition for resources between arbuscular mycorrhizal (AM) and ectomycorrhizal (ECM) plants can alter belowground mycorrhizal communities, but few studies have investigated host effects on both AM and ECM communities. In Central Mexico, the AM plant Juniperus deppeana is frequently used for reforesting areas affected by soil erosion, while the surrounding native forests are dominated by ECM oak trees. Oaks are capable of associating with both AM and ECM fungi during part of their life cycle (a feature known as dual mycorrhization) but it is unclear whether junipers possess such ability. To assess how juniper planting may affect belowground fungal interactions with oaks, we investigated mycorrhizal associations in J. deppeana and Quercus rugosa seedlings along a disturbance gradient: a native oak forest, a mixed Juniperus-Quercus population in secondary vegetation and a juniper site severely degraded by mining extraction. We measured root colonization and identified fungal communities using soil and root meta-barcoding of the ITS2 rDNA region. ECM fungal community composition was strongly affected by disturbance (regardless of host), while the community composition of AM fungi was mostly host-dependent, with a higher AM fungal richness in J. deppeana. Importantly, the fungal communities associated with Q. rugosa seedlings significantly changed in the vicinity of juniper trees, while those of J. deppeana seedlings were not affected by the presence of oak trees. Even though ECM fungal richness was higher in Q. rugosa and in the native forest, we detected a variety of ECM fungi associated exclusively with J. deppeana seedlings, suggesting that this plant species may be colonized by ECM fungi. Our results indicate that J. deppeana can alter ECM native fungal communities, with implications for its use in reforestation of mixed oak forests.

Significant changes in arbuscular mycorrhizal community and soil physicochemical properties during the saline-alkali grassland vegetation succession

Arbuscular mycorrhizal (AM) fungi are widely distributed in various habitats, and the community composition varies in response to the changing environmental conditions. To explore the response of community composition to the succession of saline-alkali land, soil samples were collected from three succession stages of Songnen saline-alkali grassland. Subsequently, the soil characteristics were determined and the AM fungi in soil samples were analyzed by high-throughput sequencing. Then, the response relationship between community composition and soil characteristics was studied by Canonical correlation and Pearson analyses. The soil properties improved with the succession of saline-alkali grassland. There was no significant difference in alpha diversity between the first and second succession stage (Suaeda glauca and Puccinellia tenuiflora, respectively), and the microbial community had a dense association network at the third stage (Leymus chinensis); in addition, each succession stage had significantly enriched amplicon sequence variants (ASVs) and functional pathways. All the soil properties except cellulase activity had significant effects on community composition. Furthermore, the pH, organic carbon, organic matter, and sucrase activity significantly correlated with alpha diversity indices. These results provide a theoretical basis for realizing the significant changes in AM fungal community and soil properties during the saline-alkali grassland vegetation succession.

Alterations in Arbuscular Mycorrhizal Community Along a Chronosequence of Teak (Tectona grandis) Plantations in Tropical Forests of China.

Arbuscular mycorrhizal (AM) fungi play a crucial role in promoting plant growth, enhancing plant stress resistance, and sustaining a healthy ecosystem. However, little is known about the mycorrhizal status of teak plantations. Here, we evaluated how the AM fungal communities of rhizosphere soils and roots respond to different stand ages of teak: 22, 35, 45, and 55-year-old from the adjacent native grassland (CK). A high-throughput sequencing method was used to compare the differences in soil and root AM fungal community structures. In combination with soil parameters, mechanisms driving the AM fungal community were revealed by redundancy analysis and the Mantel test. Additionally, spore density and colonization rates were analyzed. With increasing stand age, the AM fungal colonization rates and spore density increased linearly. Catalase activity and ammonium nitrogen content also increased, and soil organic carbon, total phosphorous, acid phosphatase activity, available potassium, and available phosphorus first increased and then decreased. Stand age significantly changed the structure of the AM fungal community but had no significant impact on the diversity of the AM fungal community. However, the diversity of the AM fungal community in soils was statistically higher than that in the roots. In total, nine and seven AM fungal genera were detected in the soil and root samples, respectively. The majority of sequences in soils and roots belonged to Glomus. Age-induced changes in soil properties could largely explain the alterations in the structure of the AM fungal community along a chronosequence, which included total potassium, carbon-nitrogen ratio, ammonium nitrogen, catalase, and acid phosphatase levels in soils and catalase, acid phosphatase, pH, and total potassium levels in roots. Soil nutrient availability and enzyme activity were the main driving factors regulating the shift in the AM fungal community structure along a chronosequence of the teak plantations.

Arbuscular Mycorrhizal Communities in the Roots of Sago Palm in Mineral and Shallow Peat Soils

Communities of arbuscular mycorrhizal fungi (AMF) in plant roots improve host plant growth. In this study, AMF communities in the roots of the sago palm (Metroxylon sagu Rottb.) were investigated in mineral soil (MS) and shallow peat soil (SPS) in Sarawak, Malaysia. MS exhibited lower moisture content (MS, 38.1; SPS, 79.8%), higher pH (H2O) (MS, 4.6; SPS, 4.1), higher soil bulk density (MS, 1.03; SPS, 0.20 g cm−3), and higher nitrogen content (MS, 16.9; SPS, 2.7 kg m−3) than SPS at the same soil depth, while the phosphorus (P) content (Bray II) (MS, 1.6; SPS, 1.9 g P2O5 m−3) was similar. The AMF colonization rate was significantly lower in SPS (39.2 ± 12.5%) than in MS (73.2 ± 4.6%). The higher number of AMF operational taxonomic units (OTUs) was detected by amplicon sequencing of the partial small-subunit rRNA gene (MS, 78; SPS, 50). A neighbor-joining tree of obtained OTUs revealed that they belonged to Acaulosporaceae, Ambisporaceae, Claroideoglomeraceae, Gigasporaceae, and Glomeraceae. The lower abundance and diversity of AMF in SPS are possibly caused by abiotic factors, including soil physicochemical properties. Glomus and Acaulospora species detected in SPS might have strong tolerance against acidity and high soil moisture content.