Ectomycorrhizal Fungal Communities Research Articles

Ectomycorrhizal fungi alter soil food webs and the functional potential of bacterial communities.

Most of Earth's trees rely on critical soil nutrients that ectomycorrhizal fungi (EcMF) liberate and provide, and all of Earth's land plants associate with bacteria that help them survive in nature. Yet, our understanding of how the presence of EcMF modifies soil bacterial communities, soil food webs, and root chemistry requires direct experimental evidence to comprehend the effects that EcMF may generate in the belowground plant microbiome. To this end, we grew Pinus muricata plants in soils that were either inoculated with EcMF and native forest bacterial communities or only native bacterial communities. We then profiled the soil bacterial communities, applied metabolomics and lipidomics, and linked omics data sets to understand how the presence of EcMF modifies belowground biogeochemistry, bacterial community structure, and their functional potential. We found that the presence of EcMF (i) enriches soil bacteria linked to enhanced plant growth in nature, (ii) alters the quantity and composition of lipid and non-lipid soil metabolites, and (iii) modifies plant root chemistry toward pathogen suppression, enzymatic conservation, and reactive oxygen species scavenging. Using this multi-omic approach, we therefore show that this widespread fungal symbiosis may be a common factor for structuring soil food webs.IMPORTANCEUnderstanding how soil microbes interact with one another and their host plant will help us combat the negative effects that climate change has on terrestrial ecosystems. Unfortunately, we lack a clear understanding of how the presence of ectomycorrhizal fungi (EcMF)-one of the most dominant soil microbial groups on Earth-shapes belowground organic resources and the composition of bacterial communities. To address this knowledge gap, we profiled lipid and non-lipid metabolites in soils and plant roots, characterized soil bacterial communities, and compared soils amended either with or without EcMF. Our results show that the presence of EcMF changes soil organic resource availability, impacts the proliferation of different bacterial communities (in terms of both type and potential function), and primes plant root chemistry for pathogen suppression and energy conservation. Our findings therefore provide much-needed insight into how two of the most dominant soil microbial groups interact with one another and with their host plant.

Characterization of ectomycorrhizal fungal community of Abies Pindrow using sporocarp sampling, morphotyping, and metabarcoding through next-generation sequencing.

Abies pindrow, commonly known as the West-Himalayan Fir, holds great ecological importance as a native tree species in the Himalayas. Beyond its value as a fuel and timber source, it serves as a keystone species within the ecosystem. However, over recent years, extensive degradation and deforestation have afflicted A. pindrow forests. Utilizing ectomycorrhizal fungal symbionts of A. pindrow could prove pivotal in restoring these deteriorated forests. This study aimed to evaluate the diversity and composition of the ectomycorrhizal fungal community associated with A. pindrow. We employed ectomycorrhizal root tip morphotyping, sporocarp sampling, and Illumina MiSeq metabarcoding of the ITS region of fungal nrDNA. The ectomycorrhizal root tips were categorized into 10 morphotypes based on their morphological characteristics, exhibiting an average colonization rate of 74%. Sporocarp sampling revealed 22 species across 10 genera, with Russula being the most prevalent. The metabarcoding yielded 285,148 raw sequences, identifying 326 operational taxonomic units (OTUs) belonging to 193 genera, 114 families, 45 orders, 22 classes, and 6 divisions. Of these, 36 OTUs across 20 genera were ectomycorrhizal, constituting 63.1% of the fungal community. Notably, Tuber was the most abundant, representing 37.42% of the fungal population, followed by Russula at 21.06%. This study provides a comprehensive understanding of mycorrhizal symbionts of A. pindrow. The findings hold significant implications for utilizing dominant ectomycorrhizal fungi in reforestation endeavors aimed at restoring this important Himalayan conifer.

Tree species-specific differences in carbon allocation to ectomycorrhizal symbionts tightly relate to ectomycorrhizal fungal community composition

Host trees allocate photosynthates to ectomycorrhizal symbionts (ECMs) in exchange for soil nutrients, and the carbon allocation has profound effects on forest carbon sequestration. However, it is still a challenge to precisely quantify the amount of carbon allocated to ECMs and to identify factors affecting this allocation. Here, we estimated tree species-specific differences and the dynamics of carbon allocation to ECMs by 13CO2 labeling along seedling development, and explored mechanisms underlying these differences from the perspective of ECM fungal community across four tree species (evergreen Picea asperata and Quercus aquifolioides, deciduous Larix gmelinii and Betula albosinensis) and three development stages (early, middle and late of the growing season). Results showed that the proportion of 13C allocated to ECMs (P13CECMs) and ECM fungal community composition varied across tree species and seedling development. P13CECMs was higher in deciduous (3.3 ± 0.7%) trees than in evergreen trees (1.6 ± 0.3%), and higher at the late (5.2 ± 0.7%) than middle (1.8 ± 0.3%) and early (0.3 ± 0.1%) growing season. The relative abundance of the four ECM exploration types (contact, short-, medium- and long-distance) was 7.8–14.8%, nearly 50%, 25.2–31.2%, and nearly 10%, respectively, and varied significantly for contact and medium-distance types. The relative abundance of contact type was higher in deciduous than evergreen trees, and higher at the late than mid-growing stage, but the opposite was true for medium-distance type. Across tree species and seedling development, P13CECMs was positively correlated with the relative abundance of contact type, but negatively correlated with that of medium-distance type. The results suggest that carbon allocation to ECMs is tightly associated with ECM fungal community composition and highlight the critical role of ECM fungal community composition in carbon budges of forest ecosystem.

Ectomycorrhizal fungal communities in natural and urban ecosystems: Quercus humboldtii as a study case in the tropical Andes

Worldwide urban landscapes are expanding because of the growing human population. Urban ecosystems serve as habitats to highly diverse communities. However, studies focusing on the diversity and structure of ectomycorrhizal communities are uncommon in this habitat. In Colombia, Quercus humboldtii Bonpl. is an ectomycorrhizal tree thriving in tropical montane forests hosting a high diversity of ectomycorrhizal fungi. Q. humboldtii is planted as an urban tree in Bogotá (Colombia). We studied how root-associated fungal communities of this tree change between natural and urban areas. Using Illumina sequencing, we amplified the ITS1 region and analyzed the resulting data using both OTUs and Amplicon Sequence Variants (ASVs) bioinformatics pipelines. The results obtained using both pipelines showed no substantial differences between OTUs and ASVs for the community patterns of root-associated fungi, and only differences in species richness were observed. We found no significant differences in the species richness between urban and rural sites based on Fisher’s alpha or species-accumulation curves. However, we found significant differences in the community composition of fungi present in the roots of rural and urban trees with rural communities being dominated by Russula and Lactarius and urban communities by Scleroderma, Hydnangium, and Trechispora, suggesting a high impact of urban disturbances on ectomycorrhizal fungal communities. Our results highlight the importance of urban trees as reservoirs of fungal diversity and the potential impact of urban conditions on favoring fungal species adapted to more disturbed ecosystems.

Effects of Stand Types on Ectomycorrhizal Fungal Community Composition and Structure of Pinus massoniana in Subtropical Mountain Forest Ecosystems

Effects of Stand Types on Ectomycorrhizal Fungal Community Composition and Structure of Pinus massoniana in Subtropical Mountain Forest Ecosystems

Ectomycorrhizal fungi are more sensitive to high soil nitrogen levels in forests exposed to nitrogen deposition.

Ectomycorrhizal fungi are essential for nitrogen (N) cycling in many temperate forests and responsive to anthropogenic N addition, which generally decreases host carbon (C) allocation to the fungi. In the boreal region, however, ectomycorrhizal fungal biomass has been found to correlate positively with soil N availability. Still, responses to anthropogenic N input, for instance through atmospheric deposition, are commonly negative. To elucidate whether variation in N supply affects ectomycorrhizal fungi differently depending on geographical context, we investigated ectomycorrhizal fungal communities along fertility gradients located in two nemo-boreal forest regions with similar ranges in soil N : C ratios and inorganic N availability but contrasting rates of N deposition. Ectomycorrhizal biomass and community composition remained relatively stable across the N gradient with low atmospheric N deposition, but biomass decreased and the community changed more drastically with increasing N availability in the gradient subjected to higher rates of N deposition. Moreover, potential activities of enzymes involved in ectomycorrhizal mobilisation of organic N decreased as N availability increased. In forests with low external input, we propose that stabilising feedbacks in tree-fungal interactions maintain ectomycorrhizal fungal biomass and communities even in N-richsoils. By contrast, anthropogenic N input seems to impair ectomycorrhizal functions.

Community composition of phytopathogenic fungi significantly influences ectomycorrhizal fungal communities during subtropical forest succession

Ectomycorrhizal fungi (EMF) can form symbiotic relationships with plants, aiding in plant growth by providing access to nutrients and defense against phytopathogenic fungi. In this context, factors such as plant assemblages and soil properties can impact the interaction between EMF and phytopathogenic fungi in forest soil. However, there is little understanding of how these fungal interactions evolve as forests move through succession stages. In this study, we used high-throughput sequencing to investigate fungal communities in young, intermediate, and old subtropical forests. At the genus level, EMF communities were dominated by Sebacina, Russula, and Lactarius, while Mycena was the most abundant genus in pathogenic fungal communities. The relative abundances of EMF and phytopathogenic fungi in different stages showed no significant difference with the regulation of different factors. We discovered that interactions between phytopathogenic fungi and EMF maintained a dynamic balance under the influence of the differences in soil quality attributed to each forest successional stage. The community composition of phytopathogenic fungi is one of the strong drivers in shaping EMF communities over successions. In addition, the EMF diversity was significantly related to plant diversity, and these relationships varied among successional stages. Despite the regulation of various factors, the positive relationship between the diversity of phytopathogenic fungi and EMF remained unchanged. However, there is no significant difference in the ratio of the abundance of EMF and phytopathogenic fungi over the course of successions. These results will advance our understanding of the biodiversity–ecosystem functioning during forest succession.Key points•Community composition of both EMF and phytopathogenic fungi changed significantly over forest succession.•Phytopathogenic fungi is a key driver in shaping EMF community.•The effect of plant Shannon’s diversity on EMF communities changed during the forest aging process.

Potential for functional divergence in ectomycorrhizal fungal communities across a precipitation gradient.

Functional traits influence the assembly of microbial communities, but identifying these traits in the environment has remained challenging. We studied ectomycorrhizal fungal (EMF) communities inhabiting Populus trichocarpa roots distributed across a precipitation gradient in the Pacific Northwest, USA. We profiled these communities using taxonomic (meta-barcoding) and functional (metagenomic) approaches. We hypothesized that genes involved in fungal drought-stress tolerance and fungal mediated plant water uptake would be most abundant in drier soils. We were unable to detect support for this hypothesis; instead, the abundance of genes involved in melanin synthesis, hydrophobins, aquaporins, trehalose-synthases, and other gene families exhibited no significant shifts across the gradient. Finally, we studied variation in sequence homology for certain genes, finding that fungal communities in dry soils are composed of distinct aquaporin and hydrophobin gene sequences. Altogether, our results suggest that while EMF communities exhibit significant compositional shifts across this gradient, coupled functional turnover, at least as inferred using community metagenomics is limited. Accordingly, the consequences of these distinct EMF communities on plant water uptake remain critically unknown, and future studies targeting the expression of genes involved in drought stress tolerance are required.

Ectomycorrhizal fungi enhance pine growth by stimulating iron-dependent mechanisms with trade-offs in symbiotic performance.

Iron (Fe) is crucial for metabolic functions of living organisms. Plants access occluded Fe through interactions with rhizosphere microorganisms and symbionts. Yet, the interplay between Fe addition and plant-mycorrhizal interactions, especially the molecular mechanisms underlying mycorrhiza-assisted Fe processing in plants, remains largely unexplored. We conducted mesocosms in Pinus plants inoculated with different ectomycorrhizal fungi (EMF) Suillus species under conditions with and without Fe coatings. Meta-transcriptomic, biogeochemical, and X-ray fluorescence imaging analyses were applied to investigate early-stage mycorrhizal roots. While Fe addition promoted Pinus growth, it concurrently reduced mycorrhiza formation rate, symbiosis-related metabolites in plant roots, and aboveground plant carbon and macronutrient content. This suggested potential trade-offs between Fe-enhanced plant growth and symbiotic performance. However, the extent of this trade-off may depend on interactions between host plants and EMF species. Interestingly, dual EMF species were more effective at facilitating plant Fe uptake by inducing diverse Fe-related functions than single-EMF species. This subsequently triggered various Fe-dependent physiological and biochemical processes in Pinus roots, significantly contributing to Pinus growth. However, this resulted in a greater carbon allocation to roots, relatively reducing the aboveground plant carbon content. Our study offers critical insights into how EMF communities rebalance benefits of Fe-induced effects on symbiotic partners.

The impact of anthropogenic transformation of urban soils on ectomycorrhizal fungal communities associated with silver birch (Betula pendula Roth.) growth in natural versus urban soils

Betula pendula Roth. is considered a pioneering plant species important for urban ecosystems. Based on the sequencing of fungal ITS, we characterized the ectomycorrhizal (ECM) communities of twenty silver birch trees growing in a contaminated, highly anthropo-pressured urban environment and in a natural reserve site. We analysed chemical properties of each tree soil samples, focusing on effects of anthropogenic transformation. Three effects of urbanization: high heavy metal content, increased salinity and soil alkalinity, were highly correlated. The examined trees were divided into two forest and two urban clusters according to the level of anthropogenic soil change. The effect of soil transformation on the ECM communities was studied, with the assumption that stronger urban transformation leads to lower ECM vitality and diversity. The results of the study did not confirm the above hypothesis. The ECM colonization was above 80% in all clusters, but the forest clusters had significantly higher share of vital non-ECM root tips than the urban ones. Eleven mycorrhizal fungal species were identified varying from seven to nine and with seven species observed in the most contaminated urban plot. However, the lowest Shannon species diversity index was found in the most natural forest cluster. In conclusion, our findings demonstrate no significant negative effect of the urban stresses on the ECM communities of silver birch suggesting that both forest and urban trees have the potential to generate a similar set of ECM taxa.

Climatic shifts threaten alpine mycorrhizal communities above the treeline

The European Alps are experiencing more than twice the increase in air temperature observed in the rest of the world. Thus, the treeline ecotone, and the unique habitats above it, offer a preview of drastic changes in plant and animal communities. However, our knowledge about climate change impacts on microbial diversity belowground is scarce. Here we investigate how upslope shift of the treeline ecotone, associated with changes in soil nutrient content, temperature and precipitation, will influence alpine ectomycorrhizal (EM) communities of Dryas octopetala, Bistorta vivipara and Salix herbacea across different habitat types in the Alps. We also assessed the degree of EM community taxonomic composition turnover in these habitats across three different climatic projections for 2040 and 2070. Our results indicate that the specialized EM fungal communities from snowbed habitats will be mostly negatively influenced under the current trajectory of environmental shifting predicted for the region. In contrast, fungi from the treeline ecotone, having wider niches, will be positively influenced by future climate and extend upwards. In addition, our predictions of EM community turnover for putative future climatic scenarios revealed high rates of turnover across the entire alpine region. This, together with glacier retreats, will aid colonization of alpine snowbed habitats by new EM plants and associated fungi, bringing additional pressures on local mycorrhizas and likely leading to fungal species extinctions.

The Ectomycorrhizal Fungi and Soil Bacterial Communities of the Five Typical Tree Species in the Junzifeng National Nature Reserve, Southeast China.

To explore the contribution of microorganisms to forest ecosystem function, we studied the ectomycorrhizal (ECM) fungal and soil bacterial community of the five typical tree species (Pinus massoniana, PM; Castanopsis carlesii, CC; Castanopsis eyrei, CE; Castanopsis fargesii, CF; and Keteleeria cyclolepis, KC) at the Junzifeng National Nature Reserve. The results indicated that the ECM fungal and soil bacterial diversity of CC and CF was similar, and the diversity rates of CC and CF were higher than those of PM, CE, and KC. Cenococcum geophilum and unclassified_Cortinariaceae II were the most prevalent occurring ECM fungi species in the five typical tree species, followed by unclassified_Cortinariaceae I and Lactarius atrofuscus. In bacteria, the dominant bacterial genera were Acidothermus, Bradyrhizobium, Acidibacter, Candidatus_Solibacter, Candidatus_Koribacter, Roseiarcus, and Bryobacter. EMF fungi and soil bacteria were correlated with edaphic factors, especially the soil pH, TP, and TK, caused by stand development. The results show that the community characteristics of ECM fungi and bacteria in the typical tree species of the Junzifeng National Nature Reserve reflect the critical role of soil microorganisms in stabilizing forest ecosystems.

Forest structural diversity is linked to soil microbial diversity

AbstractEfforts to catalog global biodiversity have often focused on aboveground taxonomic diversity, with limited consideration of belowground communities. However, diversity aboveground may influence the diversity of belowground communities and vice versa. In addition to taxonomic diversity, the structural diversity of plant communities may be related to the diversity of soil bacterial and fungal communities, which drive important ecosystem processes but are difficult to characterize across broad spatial scales. In forests, canopy structural diversity may influence soil microorganisms through its effects on ecosystem productivity and root architecture, and via associations between canopy structure, stand age, and species richness. Given that structural diversity is one of the few types of diversity that can be readily measured remotely (e.g., using light detection and ranging—LiDAR), establishing links between structural and microbial diversity could facilitate the detection of belowground biodiversity hotspots. We investigated the potential for using remotely sensed information about forest structural diversity as a predictor of soil microbial community richness and composition. We calculated LiDAR‐derived metrics of structural diversity as well as a suite of stand and soil properties from 38 forested plots across the central hardwoods region of Indiana, USA, to test whether forest canopy structure is linked with the community richness and diversity of four key soil microbial groups: bacteria, fungi, arbuscular mycorrhizal (AM) fungi, and ectomycorrhizal (EM) fungi. We found that the density of canopy vegetation is positively associated with the taxonomic richness (alpha diversity) of EM fungi, independent of changes in plant taxonomic richness. Further, structural diversity metrics were significantly correlated with the overall community composition of bacteria, EM, and total fungal communities. However, soil properties were the strongest predictors of variation in the taxonomic richness and community composition of microbial communities in comparison with structural diversity and tree species diversity. As remote sensing tools and algorithms are rapidly advancing, these results may have important implications for the use of remote sensing of vegetation structural diversity for management and restoration practices aimed at preserving belowground biodiversity.

Mycocentric fertilisation of ectomycorrhizae-inoculated Pinus radiata during containerised production alters root microbiome and growth outcomes

ABSTRACT During containerised production in forest nurseries, seedlings are often intensively fertilised to maximise seedling survival and growth. However, this practice can inadvertently harm the development of a robust root microbiome needed for plant resilience post-planting. In this controlled study using Pinus radiata, we combined reduced fertilisation and seedling inoculation with a diverse ectomycorrhizal (ECM) community as an alternative to intensive, industry-standard fertilisation. After 9 months, we investigated growth responses and changes to ECM and non-ECM root fungal communities. Reduced fertilisation improved the belowground growth and mycorrhizal root colonisation of inoculated seedlings. Isotopic nutrient tracing determined that, under moderate fertilisation, more photosynthetically fixed carbon was allocated belowground, and root-tip nitrogen (N) accumulation, a proxy for N uptake from the soil, also increased. Fertilisation level resulted in shifts in both ECM and non-ECM fungal community composition and substantial changes in the abundance of certain fungi. This study demonstrates that employing more-mycocentric fertilisation regimes may improve plantation nursery outcomes and that interactions between ECM and non-ECM fungi within inocula should be considered when studying the role of the soil microbiome in supporting P. radiata growth during containerised production.

Climate conditions are primary predictors of the regional‐scale spatial diversity patterns of ectomycorrhizal fungi

AbstractAimSpatial models are valuable for revealing biodiversity patterns but are less commonly applied to soil microbes than to aboveground macroorganisms. Ectomycorrhizal (EM) fungi are symbiotic microbes with high taxonomic and functional diversity that are associated with forest trees. We aimed to predict regional‐scale spatial patterns of EM fungal richness and community composition.LocationForests and subalpine ecosystems in Japan, from Hokkaido to Okinawa.TaxonEM fungi (Asco‐ and Basidiomycetes).MethodsWe used EM fungal DNA sequence data from 1507 soil cores at 39 sites covering a wide range of environmental conditions. The random forest machine learning approach was applied to determine the relative importance of environmental variables (i.e. climate, soil and ecosystem productivity) and to make spatial predictions. The spatial patterns of EM fungal richness and community composition were mapped at 1‐km2 grid resolution.ResultsTemperature generally had a strong influence on EM fungal richness and community composition dissimilarity. Our regional spatial analysis revealed that (1) EM fungal richness was higher in northeastern and montane regions than in southwestern regions and low‐elevation plains, (2) different EM fungal lineages exhibited contrasting spatial diversity patterns and (3) community composition dissimilarity shifted sharply from high to low elevations, and gradually from northeastern to southwestern regions, mainly in relation to climate gradients. Areas with low applicability for spatial modelling were identified based on multidimensional environmental spaces, which will help to prioritize data collection for future research.Main ConclusionsOur study provides a baseline of the potential spatial patterns of EM fungal communities, which were explained primarily by climate variables and secondarily by soil factors and ecosystem productivity. The predicted spatial patterns may be valuable for identifying diversity hotspots and advancing the assessment of climate change impacts on ecologically important root‐associated fungi.

Simulated nitrogen deposition alters the ectomycorrhizal fungal community structure in northern Korean pine plantations

Northern temperate forests are sensitive to nitrogen deposition. Korean pines are the zonal dominant vegetation in these forest ecosystems and a typical obligate ectomycorrhizal (ECM) tree. However, the impact of varying nitrogen additions on the ectomycorrhizal fungal (ECMF) community structure in Korean pine plantations remains unclear. In this experiment, nitrogen deposition was simulated (CK = 0 kg N ha−1 yr−1, LN = 20 kg N ha−1 yr−1, MN = 40 kg N ha−1 yr−1, HN = 80 kg N ha−1 yr−1), and soil biochemical indicators, ECMF community composition, and diversity were measured. The results showed that high nitrogen addition led to increased ECMF colonization, decreased ECMF community diversity and richness, and altered the occurrence of biomarkers. The MN treatment significantly increased the Simpson index compared to the LN treatment (P < 0.05), with Amphinema sp, Tuber sp, and Tylospora asterophora identified as biomarkers in the CK, LN, and HN treatments, respectively. The HN treatment significantly reduced the Chao1 index (P < 0.05), with Inocybe quietiodor, Tarzetta catinus, Inocybe giacomi, and Russula viscida serving as biomarkers in the CK, LN, MN, and HN treatments, respectively. Nitrogen addition led to decreased soil pH and available phosphorus content, increased ammonium nitrogen content, and affected ectomycorrhiza colonization by altering the soil ECMF community structure. Among these factors, ammonium nitrogen was the most influential in changing the ECMF community structure. This research offers valuable data to help predict changes in ECMF community structure in Korean pine plantations as nitrogen additions increase.

Temporal approach to identifying ectomycorrhizal community associated with Mongolian pine in a desert environment, northern China.

To date, the ectomycorrhizal (EM) fungi community has been widely investigated with aging plantations affected by the pedologic factors. However, knowledge on the effects of phenology induced by climatic factors across the age range remains poorly understood on an intra-annual scale. Here, we sampled the fine roots of Mongolian pine (Pinus sylvestris var. mongolica) plantations at different stages of the growing season (from April to September) across three stand ages (27, 34, and 44 yr) in the Mu Us Desert, Northwest China. We aim to disentangle the community composition and structure of EM fungi, as well as the impact of climate on EM fungi. We observed that the 173 distinct EM fungal operational taxonomic units (OTUs) were identified. Geopora, Inocybe, Tomentella, and Tuber were the most frequent, and their dominance was maintained as stand aging. The richness and community composition were not significantly different with stand aging (P > 0.05). Host phenology and stand age are two important factors that have shaped the EM fungal community. The growing stage affected the beta diversity of the EM fungal community more than stand age, and this variation of the EM fungal community was closely related to seasonal climate, particularly precipitation. This improved information will provide a theoretical basis for the reforestation and rehabilitation of the Mongolian pine plantations using mycorrhizal techniques. IMPORTANCE Ectomycorrhizal (EM) fungi are particularly important for host plants in a desert ecosystem. With a high degree of plasticity, EM fungi are largely influenced by host plant and environmental variables and fundamentally contribute to the ability of individuals to adapt to environmental changes. Therefore, the EM fungi are important for Mongolian pine (Pinus sylvestris var. mongolica) plantation in a desert ecosystem. Although previous studies have concluded that multiple endogenous and exogenous processes ultimately lead to species-specific temporal patterns in EM fungal populations. We still neglect the effect of host phenology on EM fungal activity. The significance of our study is the interplay between climate-driven EM fungi and plant phenology.

High diversity of fungal ecological groups in Andean-Patagonian Nothofagus forests.

Native Andean-Patagonian Nothofagus forests harbour a unique diversity of microorganisms with diverse ecological roles. Although ectomycorrhizal associations constitute an important fragment of the biota associated with these forests, the factors affecting such communities are largely unknown. We investigated the biodiversity, relative abundance, and composition of ectomycorrhizal fungal communities in relation to two host tree species and ages and the soil properties in six monospecific and mixed evergreen-deciduous Nothofagus forests. We used the internal transcribed spacer (ITS2) region by sequencing 9,600 ectomycorrhizae (ECM) root tips for the identification of fungi. In total, 1,125 fungal taxa at the genus level distributed over 131 orders were identified. The phyla Ascomycota (34.5%) and Basidiomycota (62.1%) were the most abundant, whereas Mucoromycota (3.1%), Chytridiomycota, Cryptomycota, Olpidiomycota, and Zoopagomycota occurred less frequently. The highest taxon diversity was found in old trees, whereas young trees often exhibited a lower diversity of the associated fungi. The fungal taxa were grouped into seven broad ecological categories, of which saprotrophic associations were most common, followed by pathotrophic, pathotrophic-saprotrophic-symbiotrophic, pathotrophic-saprotrophic, and symbiotrophic associations. We did not detect significant differences in the number of taxa in each category between young and old N. dombeyi and N. obliqua. Overall, the scale of the Illumina sequencing approach allowed us to detect a fungal taxa diversity that would not be possible to find through surveys of fruiting bodies alone and that have never been observed in Nothofagus forests before. Our findings suggest the impact of the proximity between sites, the similarity of the soil conditions, and anthropogenic use of the forests on the belowground fungal community's diversity and composition. Furthermore, there were differences between above- and belowground occurrences of the edible mushrooms B. loyo and Ramaria spp. However, future research, including on EMC tips found beneath fairy rings could provide significantly better correlations with the occurrence of aboveground fruiting body.

Comparable ectomycorrhizal fungal species richness but low species similarity among native Abies alba and alien Abies grandis from provenance trials in Poland

Our study contributes to the understanding of the diversity of ectomycorrhizal fungal (ECMF) communities of native A. alba and alien A. grandis in provenance trials situated in lowland and montane regions in Poland (Central Europe). Ectomycorrhizal fungi were identified directly from field-collected root tips using PCR- and Sanger-sequencing-based methods. We found that the studied fir species had relatively high and comparable ECMF species richness (66 and 69 fungal taxa on A. grandis and A. alba, respectively). Twenty-six taxa were associated with both hosts and 83 taxa were found uniquely on one or the other fir species. The ECMF community composition and structure of A. alba and A. grandis differed substantially both at the species and the phylogenetic lineage levels. Soil parameters such as total nitrogen, magnesium and potassium content and C/N ratio appeared moderately but significantly correlated with the ECMF community assembly of both firs. The provenance of the host tree species did not appear to be a strong factor in structuring the ECMF communities. This was found despite the low number of common ECMF species and relatively high number of unique species among the individual provenances of both fir species. The results of the study suggest that locally based specificity in host–fungal communities is likely a contributing factor in the outcome of provenance trials. We posit that much insight into the role of tree provenances in shaping ECMF communities will be gained by further exploring this area of research. On the surveyed experimental forest sites of A. alba and A. grandis, fungal species of conservation concern – particularly those that were endangered and rare – have been reported. Our findings imply that tree species planted outside their natural range serve as ecologically important species because they may act as an excellent reservoir of ECMF diversity, a factor of importance in functioning forest ecosystems.

Climate change–induced stress disrupts ectomycorrhizal interaction networks at the boreal–temperate ecotone

The interaction networks formed by ectomycorrhizal fungi (EMF) and their tree hosts, which are important to both forest recruitment and ecosystem carbon and nutrient retention, may be particularly susceptible to climate change at the boreal-temperate forest ecotone where environmental conditions are changing rapidly. Here, we quantified the compositional and functional trait responses of EMF communities and their interaction networks with two boreal (Pinus banksiana and Betula papyrifera) and two temperate (Pinus strobus and Quercus macrocarpa) hosts to a factorial combination of experimentally elevated temperatures and reduced rainfall in a long-term open-air field experiment. The study was conducted at the B4WarmED (Boreal Forest Warming at an Ecotone in Danger) experiment in Minnesota, USA, where infrared lamps and buried heating cables elevate temperatures (ambient, +3.1 °C) and rain-out shelters reduce growing season precipitation (ambient, ~30% reduction). EMF communities were characterized and interaction networks inferred from metabarcoding of fungal-colonized root tips. Warming and rainfall reduction significantly altered EMF community composition, leading to an increase in the relative abundance of EMF with contact-short distance exploration types. These compositional changes, which likely limited the capacity for mycelial connections between trees, corresponded with shifts from highly redundant EMF interaction networks under ambient conditions to less redundant (more specialized) networks. Further, the observed changes in EMF communities and interaction networks were correlated with changes in soil moisture and host photosynthesis. Collectively, these results indicate that the projected changes in climate will likely lead to significant shifts in the traits, structure, and integrity of EMF communities as well as their interaction networks in forest ecosystems at the boreal-temperate ecotone.