Arbuscular Mycorrhizal Associations Research Articles

Prevalent arbuscular mycorrhizae in roots and highly variable mycobiome in leaves of epiphytic subtropical fern Ophioderma pendulum.

Endophytic and mycorrhizal fungi are crucial in facilitating plant nutrition acquisition and stress tolerance. In epiphytic habitats, plants face nutrition and water stress, but their roots are mostly nonmycorrhizal and especially lacking in arbuscular mycorrhizal associations. Ophioderma pendulum is an epiphytic fern with a partially mycoheterotrophic lifestyle, likely heavily reliant on symbiotic fungi. To characterize fungal associations in the sporophyte of O. pendulum, we focused on leaves and roots of O. pendulum, seeking to reveal the fungal communities in these organs. Roots and leaves from O. pendulum in a subtropical forest were examined microscopically to observe the morphology of fungal structures and determine the percentage of various fungal structures in host tissues. Fungal composition was profiled using metabarcoding techniques that targeted ITS2 of the nuclear ribosomal DNA. Roots were consistently colonized by arbuscular mycorrhizal fungi (Glomeromycota), especially Acaulospora. Unlike previous findings on epiphytic ferns, dark septate endophytes were rare in O. pendulum roots. Leaves were predominantly colonized by Ascomycota fungi, specifically the classes Dothideomycetes (46.88%), Eurotiomycetes (11.51%), Sordariomycetes (6.23%), and Leotiomycetes (6.14%). Across sampling sites, fungal community compositions were similar in the roots but differed significantly in the leaves. Ophioderma pendulum maintains stable, single-taxon-dominant communities in the roots, primarily featuring arbuscular mycorrhizal fungi, whereas the leaves may harbor opportunistic fungal colonizers. Our study underlines the significance of mycorrhizal fungi in the adaptation of epiphytic ferns.

Roadside disturbance promotes plant communities with arbuscular mycorrhizal associations in mountain regions worldwide

We assessed the impact of road disturbances on the dominant mycorrhizal types in ecosystems at the global level and how this mechanism can potentially lead to lasting plant community changes. We used a database of coordinated plant community surveys following mountain roads from 894 plots in 11 mountain regions across the globe in combination with an existing database of mycorrhizal–plant associations in order to approximate the relative abundance of mycorrhizal types in natural and disturbed environments. Our findings show that roadside disturbance promotes the cover of plants associated with arbuscular mycorrhizal (AM) fungi. This effect is especially strong in colder mountain environments and in mountain regions where plant communities are dominated by ectomycorrhizal (EcM) or ericoid‐mycorrhizal (ErM) associations. Furthermore, non‐native plant species, which we confirmed to be mostly AM plants, are more successful in environments dominated by AM associations. These biogeographical patterns suggest that changes in mycorrhizal types could be a crucial factor in the worldwide impact of anthropogenic disturbances on mountain ecosystems. Indeed, roadsides foster AM‐dominated systems, where AM‐fungi might aid AM‐associated plant species while potentially reducing the biotic resistance against invasive non‐native species, often also associated with AM networks. Restoration efforts in mountain ecosystems will have to contend with changes in the fundamental make‐up of EcM‐ and ErM plant communities induced by roadside disturbance.

The influence of tree genus, phylogeny, and richness on the specificity, rarity, and diversity of ectomycorrhizal fungi.

Partner specificity is a well-documented phenomenon in biotic interactions, yet the factors that determine specificity in plant-fungal associations remain largely unknown. By utilizing composite soil samples, we identified the predictors that drive partner specificity in both plants and fungi, with a particular focus on ectomycorrhizal associations. Fungal guilds exhibited significant differences in overall partner preference and avoidance, richness, and specificity to specific tree genera. The highest level of specificity was observed in root endophytic and ectomycorrhizal associations, while the lowest was found in arbuscular mycorrhizal associations. The majority of ectomycorrhizal fungal species showed a preference for one of their partner trees, primarily at the plant genus level. Specialist ectomycorrhizal fungi were dominant in belowground communities in terms of species richness and relative abundance. Moreover, all tree genera (and occasionally species) demonstrated a preference for certain fungal groups. Partner specificity was not related to the rarity of fungi or plants or environmental conditions, except for soil pH. Depending on the partner tree genus, specific fungi became more prevalent and relatively more abundant with increasing stand age, tree dominance, and soil pH conditions optimal for the partner tree genus. The richness of partner tree species and increased evenness of ectomycorrhizal fungi in multi-host communities enhanced the species richness of ectomycorrhizal fungi. However, it was primarily the partner-generalist fungi that contributed to the high diversity of ectomycorrhizal fungi in mixed forests.

Evolution of endosymbiosis-mediated nuclear calcium signaling in land plants

The ability of fungi to establish mycorrhizal associations with plants and enhance the acquisition of mineral nutrients stands out as a key feature of terrestrial life. Evidence indicates that arbuscular mycorrhizal (AM) association is a trait present in the common ancestor of land plants,1,2,3,4 suggesting that AM symbiosis was an important adaptation for plants in terrestrial environments.5 The activation of nuclear calcium signaling in roots is essential for AM within flowering plants.6 Given that the earliest land plants lacked roots, whether nuclear calcium signals are required for AM in non-flowering plants is unknown. To address this question, we explored the functional conservation of symbiont-induced nuclear calcium signals between the liverwort Marchantia paleacea and the legume Medicago truncatula. In M.paleacea, AM fungi penetrate the rhizoids and form arbuscules in the thalli.7 Here, we demonstrate that AM germinating spore exudate (GSE) activates nuclear calcium signals in the rhizoids of M.paleacea and that this activation is dependent on the nuclear-localized ion channel DOES NOT MAKE INFECTIONS 1 (MpaDMI1). However, unlike flowering plants, MpaDMI1-mediated calcium signaling is only required for the thalli colonization but not for the AM penetration within rhizoids. We further demonstrate that the mechanism of regulation of DMI1 has diverged between M.paleacea and M.truncatula, including a key amino acid residue essential to sustain DMI1 in an inactive state. Our study reveals functional evolution of nuclear calcium signaling between liverworts and flowering plants and opens new avenues of research into the mechanism of endosymbiosis signaling.

A receptor required for chitin perception facilitates arbuscular mycorrhizal associations and distinguishes root symbiosis from immunity

Plants establish symbiotic associations with arbuscular mycorrhizal fungi (AMF) to facilitate nutrient uptake, particularly in nutrient-limited conditions. This partnership is rooted in the plant's ability to recognize fungal signaling molecules, such as chitooligosaccharides (chitin) and lipo-chitooligosaccharides. In the legume Medicago truncatula, chitooligosaccharides trigger both symbiotic and immune responses via the same lysin-motif-receptor-like kinases (LysM-RLKs), notably CERK1 and LYR4. The nature of plant-fungal engagement is opposite according to the outcomes of immunity or symbiosis signaling, and as such, discrimination is necessary, which is challenged by the dual roles of CERK1/LYR4 in both processes. Here, we describe a LysM-RLK, LYK8, that is functionally redundant with CERK1 for mycorrhizal colonization but is not involved in chitooligosaccharides-induced immunity. Genetic mutation of both LYK8 and CERK1 blocks chitooligosaccharides-triggered symbiosis signaling, as well as mycorrhizal colonization, but shows no further impact on immunity signaling triggered by chitooligosaccharides, compared with the mutation of CERK1 alone. LYK8 interacts with CERK1 and forms a receptor complex that appears essential for chitooligosaccharides activation of symbiosis signaling, with the lyk8/cerk1 double mutant recapitulating the impact of mutations in the symbiosis signaling pathway. We conclude that this novel receptor complex allows chitooligosaccharides activation specifically of symbiosis signaling and helps the plant to differentiate between activation of these opposing signaling processes.

Soil nutrient availability and understorey composition beneath plantations of ecto- and arbuscular mycorrhizal Chilean native trees

Abstract Background and aims Several lines of evidence indicate that arbuscular mycorrhizal (AM) and ectomycorrhizal (ECM) associations can have different effects on soil nutrient dynamics. Some lineages of ECM fungi can extract N from organic matter, with varying impacts on decomposers, soil carbon pools, mineral N availability, and plants that lack ECM. However, these effects are not always observed, and it is not clear how they are mediated by environmental factors. Methods We used Plant Root Simulator probes to compare soil availability of a wide range of nutrients beneath replicated 30-yr old plantations of Chilean Nothofagus (ECM) and Cupressaceae (Austrocedrus, Fitzroya: AM) on a lowland temperate site. Probes were buried for two 8-week periods in early spring and late summer. We also compared understorey composition beneath plantations, to test for evidence of different successional trajectories beneath Nothofagus and Cupressaceae. Results Soil organic carbon, total N and total phosphorus did not differ significantly between Nothofagus and Cupressaceae stands. Redundancy analysis revealed significant effects of both plantation type (Nothofagus vs. Cupressaceae) and season on overall mineral nutrient availability. Mineral N availability did not differ significantly between Nothofagus and Cupressaceae plots, but pH and calcium availability were significantly lower beneath Nothofagus. Manganese (Mn) was much more available beneath Nothofagus stands, which might reflect abundant Mn-peroxidase, a key enzyme involved in breakdown of lignin by ECM fungi. Understorey composition varied considerably between individual plantations, but did not differ significantly between Nothofagus and Cupressaceae plantations. Conclusions Despite an overall effect on the stoichiometry of nutrient availability, we found little evidence of modification of the local N cycle by ECM fungi, or of divergent regeneration patterns beneath AM and ECM plantations. This might reflect the relatively N-rich character of this site, and/or mycorrhizal effects being counteracted by leaf trait differences between Chilean Cupressaceae and Nothofagus species.

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

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

Arbuscular mycorrhizal fungi association and root rot disease in mungbean (<i>Vigna radiata</i>) growing areas of Haryana

The study was carried out during rainy (kharif) seasons of 2021 and 2022 at Chaudhary Charan Singh Haryana Agricultural University, Hisar, Haryana to provide a comprehensive understanding of how the presence and activity of arbuscular mycorrhizal (AM) fungi may influence the development of root rot in mungbean (Vigna radiata L.) crops in different mungbean-growing areas of Haryana. Root colonization by AM fungi in Hisar, Bhiwani, Mahendragarh, and Charkhi Dadri districts of Haryana ranged from 16.45 to 24.07%, 7.71 to 16.73%, 7.02 to 21.43% and 7.59 to 22.28%, respectively. This variability underscores the diverse interactions between mungbean plants and AM fungi in these distinct geographical regions, reflecting the influence of environmental factors and local soil conditions on mycorrhizal associations. Sporocarp numbers in these districts ranged from 76.5 to 131.5, 37 to 102, 54 to 119.5 and 65.5 to 118 per 100 g of soil, respectively. These findings emphasize the dynamic nature of AM fungal populations and their potential impact on the overall soil health and plant-microbe interactions in mungbean cultivation. Similarly, root rot incidence in these districts varied from 6.59 to 11.62%, 7.48 to 11.29%, 7.05 to 11.43% and 5.88 to 11.76%, while root rot intensity ranged from 2.77 to 4.82%, 2.70 to 4.61%, 2.06 to 4.61% and 2.43 to 4.85% in Hisar, Bhiwani, Mahendragarh, and Charkhi Dadri districts, respectively. This variability in root rot incidence and intensity highlights the susceptibility of mungbean crops to this detrimental disease and emphasizes the importance of region-specific strategies for disease management.

Arbuscular mycorrhizal fungal association in bryophytes from Arunachal Pradesh: a first report

Arbuscular mycorrhizal fungal association in bryophytes from Arunachal Pradesh: a first report

Arbuscular mycorrhizal fungal community association determines the production of flavonoids and chlorogenic acid in Acer truncatum Bunge

Arbuscular mycorrhizal (AM) fungi can affect plant secondary metabolic pathways, but how the composition and function of AM fungal communities affect the secondary metabolite content of Acer truncatum Bunge remains unknown. Ten typical A. truncatum plantations were used in southern Shaanxi province. The entropy weight method was applied to construct two grades of A. truncatum tree plantations (ordinary and superior). The interaction between AM fungi and trees in the different grades of plantations was compared. The effects of AM fungal community, soil fertility, climatic factors, and plant nutrients on the contents of flavonoids and chlorogenic acid in leaves were studied. There were no differences in the α and β diversity of AM fungal associations among different grades of trees, but the hyphal colonization rate and co-occurrence network characteristics were different. There were no differences in plant height and diameter at breast height (DBH), but higher flavonoid and chlorogenic acid contents were found in the leaves of superior trees compared to ordinary trees, and this difference was attributed to variations in their AM fungal communities. For A. truncatum trees of similar growth (same height and DBH), the abundance of AM fungi was positively correlated with leaf flavonoids and chlorogenic acid contents in superior tree grade stands, but negatively correlated in ordinary tree stands. The positive correlation between leaf flavonoid content and soil fertility in superior tree grade was mediated by the β diversity of AM fungi recruited in this environment. The relative abundance of VTX00069 and VTX00156 was positively correlated with leaf flavonoid and chlorogenic acid contents, which provides direction for the selection of AM fungi that promote flavonoids and chlorogenic acid production in A. truncatum leaves. Overall, the effect of specific AM fungal communities in the rhizosphere soil of A. truncatum on its flavonoids and chlorogenic acid contents is direct and important. This study provides new insights into enhancing the production of secondary metabolites in A. truncatum.

Making partners in the city: impact of urban soil P enrichment on the partnership between an invasive herb and arbuscular mycorrhizal fungi in a tropical city.

The mutualistic relationship between plants and arbuscular mycorrhizal (AM) fungi is essential for optimal plant nutrition, enabling plants to better withstand biotic and abiotic stressors and enhancing survival, reproduction, and colonization of new environments. Activities, such as soil enrichment or compaction, may decrease the benefits of AM fungi for plants, potentially reducing interactions in urban environments. Here, we examine this prediction by studying how urbanization alters AM interactions with the invasive herb Ruellia nudiflora (Acanthaceae). We collected soil and plants from deep urban sites (DUS; e.g., sidewalks), open urban sites (OUS; parks), and rural sites (RS) to analyse soil nutrient content, plant morphology, AM colonization rates, spore density, richness, and diversity. Contrary to predicted, DUS had the lowest soil nutrient concentration, except for phosphorus, reducing AM colonization. This supports the prediction of reduced AM interactions in urban environments. We also found that potassium affects the AM association. Urban plants had smaller and more compact root systems compared to their rural counterparts, but there were no discernible differences in AM fungi communities between urban and rural environments. Phosphorus enrichment in sidewalks is the main driver of reductionof R. nudiflora-AM fungi interactions in Mérida. More studies are needed to gain a better understanding of how AM fungi contribute to plant colonization in urban environments.

Can mycorrhizal fungi fix farming? Benefits and limitations of applying them to agroecosystems

The intensification of agriculture over the past decades has helped increase crop yields but has also led to various environmental issues, potentially undermining future productivity. One of the options considered for increasing the sustainability of agriculture is the stimulation or enhancement of microorganisms that associate with plants and help them acquire more nutrients from the soil leading to benefits such as increased growth. One key player considered are arbuscular mycorrhizal fungi (AMF), a group of below-ground fungi that form symbiotic relationships with the vast majority of land plants. However, evidence from lab and field trials suggests that not all plants respond equally to colonization by these fungi, and research is on-going to better understand the context-dependency of the symbiosis. Moreover, introducing AMF to agricultural fields through the application of commercial inoculants that contain fungal spores and hyphae has been inconsistent in their desired effects of boosting crop yield and quality. Recently, a quality framework has been put forward to try and increase the reliability of these inocula so farmers can make better use of them. Although further research on the fundamental and applied aspects of plant–arbuscular mycorrhizal associations is required, agricultural practices that favour these fungi should be encouraged as they are likely to lead to wider benefits and ultimately contribute to a more sustainable agricultural system.

Multiple facets of cutting-edge mycorrhizal research: 11th International Conference on Mycorrhiza (ICOM 11), Beijing, China, August 2022: 11th International Conference on Mycorrhiza (ICOM 11), Beijing, China, 1-5 August 2022.

Multiple facets of cutting-edge mycorrhizal research: 11th International Conference on Mycorrhiza (ICOM 11), Beijing, China, August 2022: 11th International Conference on Mycorrhiza (ICOM 11), Beijing, China, 1-5 August 2022.

Scale‐dependent diversity–biomass relationships can be driven by tree mycorrhizal association and soil fertility

AbstractDiversity–biomass relationships (DBRs) often vary with spatial scale in terrestrial ecosystems, but the mechanisms driving these scale‐dependent patterns remain unclear, especially for highly heterogeneous forest ecosystems. This study explores how mutualistic associations between trees and different mycorrhizal fungi, i.e., arbuscular mycorrhizal (AM) vs. ectomycorrhizal (EM) association, modulate scale‐dependent DBRs. We hypothesized that in soil‐heterogeneous forests with a mixture of AM and EM tree species, (i) AM and EM tree species would respond in contrasting ways (i.e., positively vs. negatively, respectively) to increasing soil fertility, (ii) AM tree dominance would contribute to higher tree diversity and EM tree dominance to greater standing biomass, and that as a result (iii) mycorrhizal associations would exert an overall negative effect on DBRs across spatial scales. To empirically test these hypotheses, we collected detailed tree distribution and soil information (e.g., nitrogen, phosphorus, organic matter, pH) from seven temperate and subtropical AM–EM mixed forest megaplots (16–50 ha). Using a spatial codispersion null model and structural equation modeling, we identified the relationships among AM or EM tree dominance, soil fertility, tree species diversity, and biomass and, thus, DBRs across 0.01‐ to 1‐ha scales. We found the first evidence overall supporting the three aforementioned hypotheses in these AM–EM mixed forests: (i) In most forests, with increasing soil fertility, tree communities changed from EM‐dominated to AM‐dominated; (ii) increasing AM tree dominance had an overall positive effect on tree diversity and a negative effect on biomass, even after controlling for soil fertility and number of trees. Together, (iii) the changes in mycorrhizal dominance along soil fertility gradients weakened the positive DBR observed at 0.01‐ to 0.04‐ha scales in nearly all forests and drove negative DBRs at 0.25‐ to 1‐ha scales in four out of seven forests. Hence, this study highlights a soil‐related mycorrhizal dominance mechanism that could partly explain why, in many natural forests, biodiversity–ecosystem functioning (BEF) relationships shift from positive to negative with increasing spatial scale.

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

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

Insect‐plant‐fungus interactions in mycorrhizal associations, with a focus on spittlebugs and ectomycorrhizal host plants

Abstract Mycorrhizal plants mediate interactions between their root‐associated fungal symbionts and insect herbivores. Arbuscular mycorrhizal (AM) associations tend to boost phloem sap sucking insects and host specialist chewing insects but depress host generalist chewing insects. In turn, insect herbivores have only small negative effects on the abundance of AM fungi. Ectomycorrhizal (EM) associations, less studied, have no consistent effect on phloem sap‐sucking or chewing insects, but their insect herbivores have strong negative effects on EM fungal abundance. Spittlebugs (Hemiptera: Cercopoidea) feed on xylem sap and are disproportionately associated with EM plants, probably because many EM fungi are especially well equipped to access nitrogen (N) from complex soil organic matter. Assimilated N is transported in host plant xylem sap as amino acids, the primary food source for xylem‐feeding insects. Although EM plants account for only 2% of all vascular plants, about 19% of spittlebugs have EM primary hosts. This compares to 9% of hosts that are rhizobial or actinorhizal N‐fixing plants, alternative modes of root‐associated N acquisition that also attract spittlebugs. Notable spittlebug EM host plants include Pinus and Abies (Pinaceae), Quercus, Alnus and Betula (Fagales), Salix (Salicaceae), Eucalyptus (Myrtaceae) and the gymnosperm Gnetum (Gnetales). Some EM plants, including several Pinus species, host spittlebug pests and some play an important role in the ecology of spittlebug vectors of the bacterial plant pathogen Xylella fastidiosa. The fossil record and dated molecular phylogenies suggest that spittlebugs initially evolved in parallel with EM Pinaceae.

Nutrition vs association: plant defenses are altered by arbuscular mycorrhizal fungi association not by nutritional provisioning alone

BackgroundWhile it is known that arbuscular mycorrhizal fungi (AMF) can improve nutrient acquisition and herbivore resistance in crops, the mechanisms by which AMF influence plant defense remain unknown. Plants respond to herbivory with a cascade of gene expression and phytochemical biosynthesis. Given that the production of defensive phytochemicals requires nutrients, a commonly invoked hypothesis is that the improvement to plant defense when grown with AMF is simply due to an increased availability of nutrients. An alternative hypothesis is that the AMF effect on herbivory is due to changes in plant defense gene expression that are not simply due to nutrient availability. In this study, we tested whether changes in plant defenses are regulated by nutritional provisioning alone or the response of plant to AMF associations. Maize plants grown with or without AMF and with one of three fertilizer treatments (standard, 2 × nitrogen, or 2 × phosphorous) were infested with fall armyworm (Spodoptera frugiperda; FAW) for 72 h. We measured general plant characteristics (e.g. height, number of leaves), relative gene expression (rtPCR) of three defensive genes (lox3, mpi, and pr5), total plant N and P nutrient content, and change in FAW mass per plant.ResultsWe found that AMF drove the defense response of maize by increasing the expression of mpi and pr5. Furthermore, while AMF increased the total phosphorous content of maize it had no impact on maize nitrogen. Fertilization alone did not alter upregulation of any of the 3 induced defense genes tested, suggesting the mechanism through which AMF upregulate defenses is not solely via increased N or P plant nutrition.ConclusionThis work supports that maize defense may be optimized by AMF associations alone, reducing the need for artificial inputs when managing FAW.

Mycorrhizal type of woody plants influences understory species richness in British broadleaved woodlands.

Summary Mature temperate woodlands are commonly dominated by ectomycorrhizal trees, whereas understory plants predominantly form arbuscular mycorrhizal associations. Due to differences in plant–fungus compatibility between canopy and ground layer vegetation the ‘mycorrhizal mediation hypothesis’ predicts that herbaceous plant establishment may be limited by a lack of suitable mycorrhizal fungal inoculum.We examined plant species data for 103 woodlands across Great Britain recorded in 1971 and in 2000 to test whether herbaceous plant species richness was related to the proportion of arbuscular mycorrhizal woody plants. We compared the effect of mycorrhizal type with other important drivers of woodland plant species richness.We found a positive effect of the relative abundance of arbuscular mycorrhizal woody plants on herbaceous plant species richness. The size of the observed effect was smaller than that of pH. Moreover, the effect persisted over time, despite many woodlands undergoing marked successional change and increased understorey shading.This work supports the mycorrhizal mediation hypothesis in British woodlands and suggests that increased abundance of arbuscular mycorrhizal woody plants is associated with greater understory plant species richness.

Proximal and distal mechanisms through which arbuscular mycorrhizal associations alter terrestrial denitrification

Proximal and distal mechanisms through which arbuscular mycorrhizal associations alter terrestrial denitrification

Higher diversity and contribution of soil arbuscular mycorrhizal fungi at an optimal P-input level

As not only an indicator but also key determinants of soil health, the performance of arbuscular mycorrhizal (AM) fungi under intensive cropping systems remains incompletely understood, particularly with regard to quantitative contributions to crop phosphorus (P) acquisition and scientific managements of P-input levels. Here, we firstly investigated the diversity and vitality of AM fungi along with decreasing P-input levels from P100 (local regular rate) to P50 (50 % off) in a greenhouse experiment to explore the optimal P-input level, and further determined the apparent contribution of AM fungi to maize (Zea mays L.) P acquisition at optimal level in a field microplot experiment with root mycorrhization inhibition by benomyl application and in another pot experiment upon AM fungal inoculation in a sterilized soil. Decreasing P input decreased the amount but increased the efficiency of plant P acquisition, and increased the diversity and colonization of AM fungi, in addition to shaping the community composition. Notably, P80 (20 % off) appeared to be an optimal level that balanced mycorrhizal vitality, maize growth and P-acquisition efficiency. The apparent contribution of AM fungi to maize P acquisition determined in both field and pot experiments were approximately 36 % and 21 % at P80 and P100, respectively, while grain yields at P80 with mycorrhizae reached the level equivalent to that of P100 without mycorrhizae, indicating a replacement of 20 % of P fertilizers by adequate mycorrhizal management. It highlights that stronger AM associations by optimizing P input allow for relatively high crop P-acquisition efficiency upon high mycorrhizal benefits, favoring agricultural production in a sustainable manner with reduced dependence on inputs.