Summer temperature increase has distinct effects on the ectomycorrhizal fungal communities of moist tussock and dry tundra in Arctic Alaska

Temperature governs the community assembly of root-associated ectomycorrhizal fungi in alpine forests on the Qinghai-Tibetan Plateau

Unraveling the assembly processes of ectomycorrhizal (ECM) fungal communities in changing environments is crucial for forecasting the impacts of climate change on forests. However, the assembly processes and key drivers of root-associated ECM fungal communities in alpine coniferous forests remain poorly understood. To address this knowledge gap, we conducted sampling in 65 monodominant alpine coniferous forests, which encompass 11 plant species belonging to three genera (Abies, Pinus, and Picea) within the Pinaceae family, all located on the Qinghai-Tibetan Plateau. We employed a combination of null model and multivariate analyses to elucidate the drivers and assembly processes of ECM fungal communities. Our results revealed significant variation in the composition and diversity of root-associated ECM fungal communities among Abies, Pinus, and Picea, indicating specific preferences for ECM fungi among Pinaceae genera. Importantly, mean annual temperature (MAT) emerged as the primary driver of these variations and regulated the assembly processes within the community of root-associated ECM fungi. As MAT temperature, the α-diversity of these fungi significantly decreased, suggesting that increased temperature may reduce the species diversity of root-associated ECM fungi in alpine forests. Furthermore, stochastic processes, such as dispersal limitation and drift, became more influential as MAT increased. Conversely, the role of deterministic processes, particularly heterogeneous selection, in shaping the ECM fungal community assembly weakened with increasing MAT. This study provides novel theoretical insights into the processes of ECM fungal community assembly in alpine forests, emphasizing the pivotal role of temperature in regulating the assembly processes and compositional dynamics of root-associated ECM fungal communities in these unique environments.

Variations in ectomycorrhizal exploration types parallel seedling fine root traits of two temperate tree species under extreme drought and contrasting solar radiation treatments

High solar radiation exacerbated the negative effects of extreme drought on plant growth and fine root traits. Ectomycorrhizae did not compensate for fine roots under drought stress. Fine roots biomass determined the role of ectomycorrhizal fungi, supporting the energy limitation hypothesis.

An Integrative Study of Mycobiome in Different Habitats from a High Arctic Region: Diversity, Distribution, and Functional Role

In the Arctic ecosystems, fungi are crucial for interactions between soil and plants, the cycling of nutrients, and the transport of carbon. To date, no studies have been conducted to thoroughly examine the mycobiome and its functional role in various habitats of the High Arctic region. The aim was to unravel the mycobiome in the nine habitats (i.e., soil, lichen, vascular plant, moss, freshwater, seawater, marine sediment, dung, and marine alga) in the Ny-Ålesund Region (Svalbard, High Arctic) using a high-throughput sequencing approach. A total of 10,419 ASVs were detected. Among them, 7535 ASVs were assigned to unidentified phyla, while the remaining 2884 ASVs were assigned to 11 phyla, 33 classes, 81 orders, 151 families, 278 genera, and 261 species that were known. The distribution of the mycobiome was driven by habitat specificity, indicating that habitat filtering is a crucial factor influencing the fungal assemblages at a local scale in this High Arctic region. Six growth forms and 19 fungal guilds were found. The ecological guild (e.g., lichenized, ectomycorrhizal) and growth form (e.g., yeast, thallus photosynthetic) varied significantly among various habitats. In addition, the occurrence of 31 fungal species that are considered to be potential pathogens was determined. These results will increase our understanding of fungal diversity and its functional significance in this distinctive High Arctic area and thereby establish the groundwork for prediction about how the mycobiome will alter in various environments as a result of anticipated climate change.

Structure and Function Analysis of Cultivated Meconopsis integrifolia Soil Microbial Community Based on High-Throughput Sequencing and Culturability

(1) Background: The structure, function, and community interactions of soil microbial communities of cultivated Meconopsis integrifolia were characterized by studying this alpine flower and traditional endangered Tibetan medicine. (2) Methods: Soil bacteria and fungi were studied based on high-throughput sequencing technology. Bacteria were isolated using culturomics and functionally identified as IAA-producing, organic phosphorus-dissolving, inorganic phosphorus-dissolving, and iron-producing carriers. (3) Results: The dominant bacterial phyla were found to be Proteobacteria and Acidobacteria, and unclassified_Rhizobiales was the most abundant genus. Ascomycota and Mortierellomycota were the dominant fungal phyla. The bacteria were mainly carbon and nitrogen metabolizers, and the fungi were predominantly Saprotroph-Symbiotroph. The identified network was completely dominated by positive correlations, but the fungi were more complex than the bacteria, and the bacterial keystones were unclassified_Caulobacteraceae and Pedobacter. Most of the keystones of fungi belonged to the phyla Ascomycetes and Basidiomycota. The highest number of different species of culturable bacteria belonged to the genus Streptomyces, with three strains producing IAA, 12 strains solubilizing organic phosphorus, one strain solubilizing inorganic phosphorus, and nine strains producing iron carriers. (4) Conclusions: At the cost of reduced ecological stability, microbial communities increase cooperation toward promoting overall metabolic efficiency and enabling their survival in the extreme environment of the Tibetan Plateau. These pioneering results have value for the protection of endangered Meconopsis integrifolia under global warming and the sustainable utilization of its medicinal value.

Experimental warming increases fungal alpha diversity in an oligotrophic maritime Antarctic soil

The climate of maritime Antarctica has altered since the 1950s. However, the effects of increased temperature, precipitation and organic carbon and nitrogen availability on the fungal communities inhabiting the barren and oligotrophic fellfield soils that are widespread across the region are poorly understood. Here, we test how warming with open top chambers (OTCs), irrigation and the organic substrates glucose, glycine and tryptone soy broth (TSB) influence a fungal community inhabiting an oligotrophic maritime Antarctic fellfield soil. In contrast with studies in vegetated soils at lower latitudes, OTCs increased fungal community alpha diversity (Simpson's index and evenness) by 102-142% in unamended soil after 5 years. Conversely, OTCs had few effects on diversity in substrate-amended soils, with their only main effects, in glycine-amended soils, being attributable to an abundance of Pseudogymnoascus. The substrates reduced alpha and beta diversity metrics by 18-63%, altered community composition and elevated soil fungal DNA concentrations by 1-2 orders of magnitude after 5 years. In glycine-amended soil, OTCs decreased DNA concentrations by 57% and increased the relative abundance of the yeast Vishniacozyma by 45-fold. The relative abundance of the yeast Gelidatrema declined by 78% in chambered soil and increased by 1.9-fold in irrigated soil. Fungal DNA concentrations were also halved by irrigation in TSB-amended soils. In support of regional- and continental-scale studies across climatic gradients, the observations indicate that soil fungal alpha diversity in maritime Antarctica will increase as the region warms, but suggest that the accumulation of organic carbon and nitrogen compounds in fellfield soils arising from expanding plant populations are likely, in time, to attenuate the positive effects of warming on diversity.

Colonization by the Mycorrhizal Helper Bacillus pumilus HR10 Is Enhanced During the Establishment of Ectomycorrhizal Symbiosis Between Hymenochaete sp. Rl and Pinus thunbergii

There are complex interactions between mycorrhizal helper bacteria (MHBs) and ectomycorrhizal (ECM) fungi, with MHBs promoting mycorrhizal synthesis and ECM fungi regulating plant rhizobacterial colonization, diversity, and function. In this study, to investigate whether the ECM fungus Hymenochaete sp. Rl affects the survival and colonization of the MHB strain Bacillus pumilus HR10 in the rhizosphere, the biomass of B. pumilus HR10 was measured in the rhizosphere and mycorrhizosphere. In addition, extracts of Hymenochaete sp. Rl and Pinus thunbergii were evaluated for their effect on B. pumilus HR10 colonization (growth, sporulation, biofilm formation, extracellular polysaccharide and extracellular protein contents, flagellar motility, and expression of colonization-related genes). The results showed that inoculation of Hymenochaete sp. Rl significantly increased the biomass of B. pumilus HR10 in the rhizosphere; however, while extracts of Hymenochaete sp. Rl and P. thunbergii did not affect the biomass or spore formation of HR10, they did affect its biofilm formation, extracellular polysaccharide and extracellular protein production, and flagellar motility. Furthermore, the addition of symbiont extracts affected the expression of chemotaxis-related genes in HR10. When the extracts were added separately, the expression of srf genes in HR10 increased; when the extracts were added simultaneously, the expression of the flagellin gene fliG in HR10 increased, but there was no significant effect on the expression of srf genes, consistent with the results on biofilm production. Thus, Hymenochaete sp. Rl and P. thunbergii roots had a positive effect on colonization by B. pumilus HR10 at the rhizosphere level through their secretions.

Elevation Matters More than Season in Shaping the Heterogeneity of Soil and Root Associated Ectomycorrhizal Fungal Community

Ectomycorrhizal (EcM) fungi play important roles in forest ecosystems, and their richness and composition can change along with elevation and season changes. However, no study has estimated the relative importance of altitudinal and seasonal heterogeneity in predicting the distribution of EcM fungal communities by simultaneously considering different sample types (root versus soil). In this study, we collected root and soil samples along a > 1,500-m elevation gradient during wet and dry seasons from Baima Snow Mountain, located in "the Mountains of Southwest China," one of the 34 biodiversity hot spots, and we analyzed them using next-generation sequencing. Regardless of the sample type, similar EcM fungal richness pattern with increasing elevation (decline in the forest zone, and an increase at the alpine meadow zone) and strong community turnovers among different elevational zones and between two seasons were detected, and changes of EcM fungal community similarity on 400-m altitude gradient were equivalent to the community turnover between dry and wet seasons. Elevation and edaphic factors were shown to have the largest effects on EcM fungal community. The heterogeneity of richness and community composition was stronger among different elevational zones than across different seasons, mainly because the elevation variations in the EcM fungal community were shaped by the combined effects of different environmental factors, while seasonal changes were mainly controlled by temperature and fast-changing soil nutrients. IMPORTANCE Altitude and season represent two important environmental gradients that shape the structure of biome, including the heterogeneity of EcM fungi. Previous studies have separately considered the influences of altitude and season on EcM fungal communities, but the relative importance of altitude and season is still unknown. The present study revealed that elevation influences the heterogeneity of EcM fungal community more than season; this may be because the variability of environmental factors is higher across different elevations than that across seasons.

Karst rocky desertification diverged the soil residing and the active ectomycorrhizal fungal communities thereby fostering distinctive extramatrical mycelia

Ectomycorrhizal fungi (EMF) are mutualists that play crucial roles in liberation, nutrient acquisition, transfer of growth-limiting resources and provision of water to host plants in terrestrial ecosystems, particularly in stressed prone climates. In this study, a field-based experiment was performed in Yunnan, China to assess the effect of karst rocky desertification (KRD) and natural forests (non-KRD) sites on the richness and composition of EMF communities. Inert sand-filled mesh bags were employed to characterize the active EMF and quantify the production of extramatrical mycelium (EMM). Results indicated that, EMF exhibited a significant differentiation among KRD and non-KRD sites, richness and diversity were higher across KRD areas, whereas the evenness showed the opposite trend. Ascomycota and Zygomycota were greater across KRD sites, however, Basidiomycota showed no difference across both study sites. The relative abundance of Clavaria, Butyriboletus, Odontia, Phyloporus, Helvella, Russula and Tomentella were higher across the KRD sites, whereas, Clavulinopsis, Endogone, Amanita, Inocybe and Clavulina were higher across the non-KRD sites. It's worth noting that, saprophytic (SAP) fungal community was found to be more abundant in the soil than the mesh bags at both sites particularly at KRD sites, which likely provide more free space and less competition for the EMF to thrive well in the mesh bags. In similar pattern, ergosterol concentration in mesh bags was observed relatively higher at KRD sites than the non-KRD sites. The Entoloma, Amanita, and Sebacina were found to be substantially higher in mesh bags than soil across both sites. Delicatula, Helvella and Tomentella on the other hand, showed higher relative abundance in mesh bags than soil over KRD sites, however they did not differ across non-KRD sites. Taken together, the presented results highlight relationship between the EMF community and the complex KRD environment, which is very important for the restoration of disturbed karst landscapes.

Permafrost thaw with warming reduces microbial metabolic capacities in subsurface soils

Microorganisms are major constituents of the total biomass in permafrost regions, whose underlain soils are frozen for at least two consecutive years. To understand potential microbial responses to climate change, here we examined microbial community compositions and functional capacities across four soil depths in an Alaska tundra site. We showed that a 5-year warming treatment increased soil thaw depth by 25.7% (p = .011) within the deep organic layer (15-25 cm). Concurrently, warming reduced 37% of bacterial abundance and 64% of fungal abundances in the deep organic layer, while it did not affect microbial abundance in other soil layers (i.e., 0-5, 5-15, and 45-55 cm). Warming treatment altered fungal community composition and microbial functional structure (p < .050), but not bacterial community composition. Using a functional gene array, we found that the relative abundances of a variety of carbon (C)-decomposing, iron-reducing, and sulphate-reducing genes in the deep organic layer were decreased, which was not observed by the shotgun sequencing-based metagenomics analysis of those samples. To explain the reduced metabolic capacities, we found that warming treatment elicited higher deterministic environmental filtering, which could be linked to water-saturated time, soil moisture, and soil thaw duration. In contrast, plant factors showed little influence on microbial communities in subsurface soils below 15 cm, despite a 25.2% higher (p < .05) aboveground plant biomass by warming treatment. Collectively, we demonstrate that microbial metabolic capacities in subsurface soils are reduced, probably arising from enhanced thaw by warming.

Reindeer grazing history determines the responses of subarctic soil fungal communities to warming and fertilization

Composition and functioning of arctic soil fungal communities may alter rapidly due to the ongoing trends of warmer temperatures, shifts in nutrient availability, and shrub encroachment. In addition, the communities may also be intrinsically shaped by heavy grazing, which may locally induce an ecosystem change that couples with increased soil temperature and nutrients and where shrub encroachment is less likely to occur than in lightly grazed conditions. We tested how 4 yr of experimental warming and fertilization affected organic soil fungal communities in sites with decadal history of either heavy or light reindeer grazing using high-throughput sequencing of the internal transcribed spacer 2 ribosomal DNA region. Grazing history largely overrode the impacts of short-term warming and fertilization in determining the composition of fungal communities. The less diverse fungal communities under light grazing showed more pronounced responses to experimental treatments when compared with the communities under heavy grazing. Yet, ordination approaches revealed distinct treatment responses under both grazing intensities. If grazing shifts the fungal communities in Arctic ecosystems to a different and more diverse state, this shift may dictate ecosystem responses to further abiotic changes. This indicates that the intensity of grazing cannot be left out when predicting future changes in fungi-driven processes in the tundra.

Systematic analysis of Russula in the North American Rocky Mountain alpine zone

Russula (Russulales) is an important ectomycorrhizal fungal genus in Arctic and alpine regions where it occurs with Salix, Betula, Dryas, and Polygonum, yet a complex phylogenetic analysis of the genus in these habitats is lacking. This research compared collections of Russula from the Rocky Mountain alpine (Colorado, Montana, Wyoming) with reference specimens from Arctic and alpine habitats, mostly in Europe, using an in-depth morphological study and a phylogenetic analysis of the nuc rDNA internal transcribed spacer region ITS1-5.8S-ITS2 (ITS barcode) and the second largest subunit of the RNA polymerase II gene (rpb2). One hundred thirty-nine Russula collections were sequenced, including type material. Ten species are reported from alpine or treeline habitats in the Rocky Mountains. This is the first formal report of R. cf. altaica, R. saliceticola, and R. subrubens from the Rocky Mountains and of R. purpureofusca in North America. Russula laevis is reported for the first time under this name with a voucher, and not as an environmental sample. Previous reports of R. nana and R. laccata are molecularly confirmed. Two species are reported from subalpine habitats at treeline: R. montana with conifers and R. cf. altaica with Betula. In this study, R. laccata, R. subrubens, and R. laevis were collected in alpine habitats but have been reported below treeline in Europe; these species may also be present at lower elevations in North America. Most species have an intercontinental distribution and have been reported in other alpine or Arctic habitats. Two unidentified and potentially new species were only found in North America and are discussed. A key to the alpine Russulas of North America is provided.

Fungal ethnoecology: observed habitat preferences and the perception of changes in fungal abundance by mushroom collectors in Poland

BACKGROUND

Scientists frequently raise the topic of data deficiency related to the abundance and distribution of macrofungi in the context of climate change. Our study is the first detailed documentation on locals' perception of fungal ecology which covers a large mycophilous region of Europe (Mazovia, Poland).

METHODS

A total of 695 semi-structured interviews were carried out among local informants in 38 localities proportionally distributed throughout the study area (one locality approximately every 30 km). Interview questions concerned fungi species collected, their perceived habitats, and whether any changes had been noted in their abundance. As many as 556 respondents provided information concerning fungal ecology. In these descriptions, 35 taxa were mentioned by at least 5 respondents.

RESULTS

The data collected during interviews allowed us to create collective folk descriptions of habitat preferences and a list of 98 different macro-, meso-, and microhabitats of macrofungi described by the respondents. This list of recurring habitats assigned to particular macrofungal taxa coincides with, and sometimes exceeds, data available in scientific publications. Some habitat preferences observed by the informants have not yet been researched or tested by science. Out of 695 respondents, 366 (53%) noticed a steady decrease in local macrofungi abundance, and only one person claimed to have observed a steady increase. Imleria badia was the only species with increased abundance, as noted by fifteen independent respondents. The main listed reason for abundance decrease was drought (f = 186).

CONCLUSIONS

Collected information on the ecology of fungi shows that local knowledge does not generally diverge from scientific knowledge. The acquired information related to macrofungal abundance and ecology may also be used as a tool for the formulation of new scientific questions and theories. The analysis of local fungi observations might contribute to broadening knowledge about local changes in fungi and enable new estimations related to large-scale analysis of macrofungal abundance.

Glacier retreat in the High Arctic: opportunity or threat for ectomycorrhizal diversity?

Climate change causes Arctic glaciers to retreat faster, exposing new areas for colonization. Several pioneer plants likely to colonize recent deglaciated, nutrient-poor areas depend on fungal partners for successful establishment. Little is known about general patterns or characteristics of facilitating fungal pioneers and how they vary with regional climate in the Arctic. The High Arctic Archipelago Svalbard represents an excellent study system to address these questions, as glaciers cover ∼60% of the land surface and recent estimations suggest at least 7% reduction of glacier area since 1960s. Roots of two ectomycorrhizal (ECM) plants (Salix polaris and Bistorta vivipara) were sampled in eight glacier forelands. Associated ECM fungi were assessed using DNA metabarcoding. About 25% of the diversity was unknown at family level, indicating presence of undescribed species. Seven genera dominated based on richness and abundance, but their relative importance varied with local factors. The genus Geopora showed surprisingly high richness and abundance, particularly in dry, nutrient-poor forelands. Such forelands will diminish along with increasing temperature and precipitation, and faster succession. Our results support a taxonomical shift in pioneer ECM diversity with climate change, and we are likely to lose unknown fungal diversity, without knowing their identity or ecological importance.

Soil fungal community composition and functional similarity shift across distinct climatic conditions

A large part of ecosystem function in woodland systems depends on soil fungal communities. However, global climate change has the potential to fundamentally alter these communities as fungal species are filtered with changing environmental conditions. In this study, we examined the potential effects of climate on host-associated (i.e. tree-associated) soil fungal communities at climatically distinct sites in the Tehachapi Mountains in California, where more arid conditions represent likely regional climate futures. We found that soil fungal community composition changes strongly across sites, with species richness and diversity being highest at the most arid site. However, host association may buffer the effects of climate on community composition, as host-associated fungal communities are more similar to each other across climatically distinct sites than the whole fungal community. Lastly, an examination of functional traits for ectomycorrhizal fungi, a well-studied guild of fungal mutualist species, showed that stress-tolerant traits were more abundant at arid sites than mesic sites, providing a mechanistic understanding of these community patterns. Taken together, our results indicate that fungal community composition will likely shift with future climate change but that host association may buffer these effects, with shifts in functional traits having implications for future ecosystem function.

Ectomycorrhizal fungal communities associated with Larix gemelinii Rupr. in the Great Khingan Mountains, China

Larix gemelinii is an important tree species in the Great Khingan Mountains in Northeast China with a high economic and ecological value for its role in carbon sequestration and as a source of lumber and nuts. However, the ectomycorrhizal (EM) fungal diversity and community composition of this tree remain largely undefined. We examined EM fungal communities associated with L. gemelinii from three sites in the Great Khingan Mountains using Illumina Miseq to sequence the rDNA ITS2 region and evaluated the impact of spatial, soil, and climatic variables on the EM fungal community. A total of 122 EM fungal operational taxonomic units (OTUs) were identified from 21 pooled-root samples, and the dominant EM fungal lineages were /tricholoma, /tomentella-thelephora, /suillus-rhizopogon, and /piloderma. A high proportion of unique EM fungal OTUs were present; some abundant OTUs largely restricted to specific sites. EM fungal richness and community assembly were significantly correlated with spatial distance and climatic and soil variables, with mean annual temperature being the most important predictor for fungal richness and geographic distance as the largest determinant for community turnover. Our findings indicate that L. gemelinii has a rich and distinctive EM fungal community contributing to our understanding of the montane EM fungal community structure from the perspective of a single host plant that has not been previously reported.

Diversity and community structure of ectomycorrhizal fungi in Pinus thunbergii coastal forests bordering the Yellow Sea of China

Ectomycorrhizas play a fundamental role in the function of forest ecosystems, being essential for plant nutrition absorption and soil quality. Many afforestation and reforestation programmes have begun to recover and maintain coastal forests in China, using pine species including Pinus thunbergii. We investigated the ectomycorrhizal colonization status of P. thunbergii in coastal pine forests of the Yellow Sea of China. We identified a total of 53 ectomycorrhizal fungal species in 74 soil samples collected from three sites and found that Thelephoraceae (10 spp.) and Russulaceae (8 spp.) were the most species-rich ectomycorrhizal fungal lineages. Russula sp. 1 was the most abundant species, accounting for 15.3% of the total ectomycorrhizal tips identified. Most of the remaining species were rare. At this small scale, host identity had no significant effect on the ectomycorrhizal fungal community composition (A = 0.036, P = 0.258), but sampling sites did (A = 0.135, P = 0.041). In addition, Na⁺ and K⁺ content and soil pH had significant effects on the ectomycorrhizal fungal community. The ectomycorrhizal fungal community associated with different host plants will become an important new direction for research, as ectomycorrhiza may have the potential to improve host capacity to establish in salt-stressed environments. This will provide a theoretical basis and technical support for saline soil reforestation and rehabilitation using pine species with compatible, native ectomycorrhizal fungi in Yellow Sea coastal areas.

Tundra Type Drives Distinct Trajectories of Functional and Taxonomic Composition of Arctic Fungal Communities in Response to Climate Change - Results From Long-Term Experimental Summer Warming and Increased Snow Depth

The arctic tundra is undergoing climate-driven changes and there are serious concerns related to the future of arctic biodiversity and altered ecological processes under possible climate change scenarios. Arctic land surface temperatures and precipitation are predicted to increase further, likely causing major transformation in terrestrial ecosystems. As a response to increasing temperatures, shifts in vegetation and soil fungal communities have already been observed. Little is known, however, how long-term experimental warming coupled with increased snow depth influence the trajectories of soil fungal communities in different tundra types. We compared edaphic variables and fungal community composition in experimental plots simulating the expected increase in summer warming and winter snow depth, based on DNA metabarcoding data. Fungal communities in the sampled dry and moist acidic tundra communities differed greatly, with tundra type explaining ca. one-third of compositional variation. Furthermore, dry and moist tundra appear to have different trajectories in response to climate change. Specifically, while both warming and increased snow depth had significant effects on fungal community composition and edaphic variables in dry tundra, the effect of increased snow was greater. However, in moist tundra, fungal communities mainly were affected by summer warming, while increased snow depth had a smaller effect and only on some functional groups. In dry tundra, microorganisms generally are limited by moisture in the summer and extremely low temperatures in winter, which is in agreement with the stronger effect of increased snow depth relative to warming. On the contrary, moist tundra soils generally are saturated with water, remain cold year-round and show relatively small seasonal fluctuations in temperature. The greater observed effect of warming on fungi in moist tundra may be explained by the narrower temperature optimum compared to those in dry tundra.

Soil Microbes Trade-Off Biogeochemical Cycling for Stress Tolerance Traits in Response to Year-Round Climate Change

Winter air temperatures are rising faster than summer air temperatures in high-latitude forests, increasing the frequency of soil freeze/thaw events in winter. To determine how climate warming and soil freeze/thaw cycles affect soil microbial communities and the ecosystem processes they drive, we leveraged the Climate Change across Seasons Experiment (CCASE) at the Hubbard Brook Experimental Forest in the northeastern United States, where replicate field plots receive one of three climate treatments: warming (+5°C above ambient in the growing season), warming in the growing season + winter freeze/thaw cycles (+5°C above ambient +4 freeze/thaw cycles during winter), and no treatment. Soil samples were taken from plots at six time points throughout the growing season and subjected to amplicon (rDNA) and metagenome sequencing. We found that soil fungal and bacterial community composition were affected by changes in soil temperature, where the taxonomic composition of microbial communities shifted more with the combination of growing-season warming and increased frequency of soil freeze/thaw cycles in winter than with warming alone. Warming increased the relative abundance of brown rot fungi and plant pathogens but decreased that of arbuscular mycorrhizal fungi, all of which recovered under combined growing-season warming and soil freeze/thaw cycles in winter. The abundance of animal parasites increased significantly under combined warming and freeze/thaw cycles. We also found that warming and soil freeze/thaw cycles suppressed bacterial taxa with the genetic potential for carbon (i.e., cellulose) decomposition and soil nitrogen cycling, such as N fixation and the final steps of denitrification. These new soil communities had higher genetic capacity for stress tolerance and lower genetic capacity to grow or reproduce, relative to the communities exposed to warming in the growing season alone. Our observations suggest that initial suppression of biogeochemical cycling with year-round climate change may be linked to the emergence of taxa that trade-off growth for stress tolerance traits.

Ectomycorrhizal Fungi: Participation in Nutrient Turnover and Community Assembly Pattern in Forest Ecosystems

Ectomycorrhizal fungi (EcMF) are involved in soil nutrient cycling in forest ecosystems. These fungi can promote the uptake of nutrients (e.g., nitrogen (N) and phosphorus (P)) and water by host plants, as well as facilitate host plant growth and resistance to stresses and diseases, thereby maintaining the aboveground primary productivity of forest ecosystems. Moreover, EcMF can acquire the carbon (C) sources needed for their growth from the host plants. The nutrient regulation mechanisms of EcMF mainly include the decay of soil organic matter via enzymatic degradation, nonenzymatic mechanism (Fenton chemistry), and priming effects, which in turn promote C and N cycling. At the same time, EcMF can secrete organic acids and phosphatases to improve the availability of soil P, or increase mycelium inputs to facilitate plant acquisition of P. The spatiotemporal distribution of EcMF is influenced by a combination of historical factors and contemporary environmental factors. The community of EcMF is associated with various factors, such as climate change, soil conditions, and host distribution. Under global climate change, investigating the relationships between the nutrient cycling functions of EcMF communities and their distribution patterns under various spatiotemporal scales is conducive to more accurate assessments of the ecological effects of EcMF on the sustainable development of forest.

Notes, outline and divergence times of Basidiomycota

The Basidiomycota constitutes a major phylum of the kingdom Fungi and is second in species numbers to the Ascomycota. The present work provides an overview of all validly published, currently used basidiomycete genera to date in a single document. An outline of all genera of Basidiomycota is provided, which includes 1928 currently used genera names, with 1263 synonyms, which are distributed in 241 families, 68 orders, 18 classes and four subphyla. We provide brief notes for each accepted genus including information on classification, number of accepted species, type species, life mode, habitat, distribution, and sequence information. Furthermore, three phylogenetic analyses with combined LSU, SSU, 5.8s, rpb1, rpb2, and ef1 datasets for the subphyla Agaricomycotina, Pucciniomycotina and Ustilaginomycotina are conducted, respectively. Divergence time estimates are provided to the family level with 632 species from 62 orders, 168 families and 605 genera. Our study indicates that the divergence times of the subphyla in Basidiomycota are 406–430 Mya, classes are 211–383 Mya, and orders are 99–323 Mya, which are largely consistent with previous studies. In this study, all phylogenetically supported families were dated, with the families of Agaricomycotina diverging from 27–178 Mya, Pucciniomycotina from 85–222 Mya, and Ustilaginomycotina from 79–177 Mya. Divergence times as additional criterion in ranking provide additional evidence to resolve taxonomic problems in the Basidiomycota taxonomic system, and also provide a better understanding of their phylogeny and evolution.

Vegetation, pH and Water Content as Main Factors for Shaping Fungal Richness, Community Composition and Functional Guilds Distribution in Soils of Western Greenland

Fungi are the most abundant and one of the most diverse components of arctic soil ecosystems, where they are fundamental drivers of plant nutrient acquisition and recycling. Nevertheless, few studies have focused on the factors driving the diversity and functionality of fungal communities associated with these ecosystems, especially in the scope of global warming that is particularly affecting Greenland and is leading to shrub expansion, with expected profound changes of soil microbial communities. We used soil DNA metabarcoding to compare taxonomic and functional composition of fungal communities in three habitats [bare ground (BG), biological soil crusts (BSC), and vascular vegetation (VV) coverage] in Western Greenland. Fungal richness increased with the increasing complexity of the coverage, but BGs and BSCs samples showed the highest number of unique OTUs. Differences in both fungal community composition and distribution of functional guilds identified were correlated with edaphic factors (mainly pH and water content), in turn connected with the different type of coverage. These results suggest also possible losses of diversity connected to the expansion of VV and possible interactions among the members of different functional guilds, likely due to the nutrient limitation, with potential effects on elements recycling.

Mycorrhizal types differ in ecophysiology and alter plant nutrition and soil processes

Mycorrhizal fungi benefit plants by improved mineral nutrition and protection against stress, yet information about fundamental differences among mycorrhizal types in fungi and trees and their relative importance in biogeochemical processes is only beginning to accumulate. We critically review and synthesize the ecophysiological differences in ectomycorrhizal, ericoid mycorrhizal and arbuscular mycorrhizal symbioses and the effect of these mycorrhizal types on soil processes from local to global scales. We demonstrate that guilds of mycorrhizal fungi display substantial differences in genome-encoded capacity for mineral nutrition, particularly acquisition of nitrogen and phosphorus from organic material. Mycorrhizal associations alter the trade-off between allocation to roots or mycelium, ecophysiological traits such as root exudation, weathering, enzyme production, plant protection, and community assembly as well as response to climate change. Mycorrhizal types exhibit differential effects on ecosystem carbon and nutrient cycling that affect global elemental fluxes and may mediate biome shifts in response to global change. We also note that most studies performed to date have not been properly replicated and collectively suffer from strong geographical sampling bias towards temperate biomes. We advocate that combining carefully replicated field experiments and controlled laboratory experiments with isotope labelling and -omics techniques offers great promise towards understanding differences in ecophysiology and ecosystem services among mycorrhizal types.

Ectomycorrhizal fungi and soil enzymes exhibit contrasting patterns along elevation gradients in southern Patagonia

The biological and functional diversity of ectomycorrhizal (ECM) associations remain largely unknown in South America. In Patagonia, the ECM tree Nothofagus pumilio forms monospecific forests along mountain slopes without confounding effects of vegetation on plant-fungi interactions. To determine how fungal diversity and function are linked to elevation, we characterized fungal communities, edaphic variables, and eight extracellular enzyme activities along six elevation transects in Tierra del Fuego (Argentina and Chile). We also tested whether pairing ITS1 rDNA Illumina sequences generated taxonomic biases related to sequence length. Fungal community shifts across elevations were mediated primarily by soil pH with the most species-rich fungal families occurring mostly within a narrow pH range. By contrast, enzyme activities were minimally influenced by elevation but correlated with soil factors, especially total soil carbon. The activity of leucine aminopeptidase was positively correlated with ECM fungal richness and abundance, and acid phosphatase was correlated with nonECM fungal abundance. Several fungal lineages were undetected when using exclusively paired or unpaired forward ITS1 sequences, and these taxonomic biases need reconsideration for future studies. Our results suggest that soil fungi in N. pumilio forests are functionally similar across elevations and that these diverse communities help to maintain nutrient mobilization across the elevation gradient.

A single ectomycorrhizal plant root system includes a diverse and spatially structured fungal community

Although only a relatively small proportion of plant species form ectomycorrhizae with fungi, it is crucial for growth and survival for a number of widespread woody plant species. Few studies have attempted to investigate the fine scale spatial structure of entire root systems of adult ectomycorrhizal (EcM) plants. Here, we use the herbaceous perennial Bistorta vivipara to map the entire root system of an adult EcM plant and investigate the spatial structure of its root-associated fungi. All EcM root tips were sampled, mapped and identified using a direct PCR approach and Sanger sequencing of the internal transcribed spacer region. A total of 32.1% of all sampled root tips (739 of 2302) were successfully sequenced and clustered into 41 operational taxonomic units (OTUs). We observed a clear spatial structuring of the root-associated fungi within the root system. Clusters of individual OTUs were observed in the younger parts of the root system, consistent with observations of priority effects in previous studies, but were absent from the older parts of the root system. This may suggest a succession and fragmentation of the root-associated fungi even at a very fine scale, where competition likely comes into play at different successional stages within the root system.

Temperature niche position and breadth of ectomycorrhizal fungi: Reduced diversity under warming predicted by a nested community structure

Species with narrow niche breadths are assumed to be more susceptible to environmental changes than those with wide niche breadths. Although information on niche properties is necessary for predicting biological responses to environmental changes, such information is largely missing for soil microbes. In this study, we present the temperature niche positions and breadths of a functionally important group of eukaryotic soil microbes, ectomycorrhizal (EM) fungi. We compiled high-quality EM fungal sequence data from 26 forested sites in Japan (with mean annual temperatures ranging from 1.6 to 23.6°C) to create temperature niche profiles for each individual fungal species. Nested theory and a newly developed weighted-randomization null model were applied to 75 fungal operational taxonomic units (OTUs) with high occurrence records to examine potential preferences for certain temperature positions and breadths. Our analyses revealed that (a) many EM fungal OTUs were restricted to habitats with low mean annual temperatures, (b) fungal OTUs observed at colder sites exhibited narrower temperature breadths than expected by chance, (c) the composition of EM fungal OTUs exhibited a nested pattern along the temperature gradient, and (d) EM fungal richness was highest at colder sites, where the greatest degree of overlap in OTU occurrence was observed. These findings imply that future warming may limit the distribution of many EM fungal species that are currently adapted to only cold climates. This could eventually reduce EM fungal biodiversity, which is linked to forest function through symbiotic associations with trees. This study demonstrates the distribution and environmental ranges of various EM fungal species and can contribute to develop species distribution models with the aim of conserving microbes in the face of climate change.

Patterns in Ectomycorrhizal Diversity, Community Composition, and Exploration Types in European Beech, Pine, and Spruce Forests

Ectomycorrhizal (EM) fungi are pivotal drivers of ecosystem functioning in temperate and boreal forests. They constitute an important pathway for plant-derived carbon into the soil and facilitate nitrogen and phosphorus acquisition. However, the mechanisms that drive ectomycorrhizal diversity and community composition are still subject to discussion. We investigated patterns in ectomycorrhizal diversity, community composition, and exploration types on root tips in Fagus sylvatica,Picea abies, and Pinus sylvestris stands across Europe. Host tree species is the most important factor shaping the ectomycorrhizal community as well as the distribution of exploration types. Moreover, abiotic factors such as soil properties, N deposition, temperature, and precipitation, were found to significantly influence EM diversity and community composition. A clear differentiation into functional traits by means of exploration types was shown for all ectomycorrhizal communities across the three analyzed tree species. Contact and short-distance exploration types were clearly significantly more abundant than cord- or rhizomorph-forming long-distance exploration types of EM fungi. Medium-distance exploration types were significantly lower in abundance than contact and short-distance types, however they were the most frequent EM taxa and constituted nearly half of the EM community. Furthermore, EM taxa exhibit distinct ecological ranges, and the type of soil exploration seemed to determine whether EM taxa have small or rather big environmental ranges.

Changes in composition and abundance of functional groups of arctic fungi in response to long-term summer warming

We characterized fungal communities in dry and moist tundra and investigated the effect of long-term experimental summer warming on three aspects of functional groups of arctic fungi: richness, community composition and species abundance. Warming had profound effects on community composition, abundance, and, to a lesser extent, on richness of fungal functional groups. In addition, our data show that even within functional groups, the direction and extent of response to warming tend to be species-specific and we recommend that studies on fungal communities and their roles in nutrient cycling take into account species-level responses.

Abrupt changes in the composition and function of fungal communities along an environmental gradient in the high Arctic

Fungi play a key role in soil-plant interactions, nutrient cycling and carbon flow and are essential for the functioning of arctic terrestrial ecosystems. Some studies have shown that the composition of fungal communities is highly sensitive to variations in environmental conditions, but little is known about how the conditions control the role of fungal communities (i.e., their ecosystem function). We used DNA metabarcoding to compare taxonomic and functional composition of fungal communities along a gradient of environmental severity in Northeast Greenland. We analysed soil samples from fell fields, heaths and snowbeds, three habitats with very contrasting abiotic conditions. We also assessed within-habitat differences by comparing three widespread microhabitats (patches with high cover of Dryas, Salix, or bare soil). The data suggest that, along the sampled mesotopographic gradient, the greatest differences in both fungal richness and community composition are observed amongst habitats, while the effect of microhabitat is weaker, although still significant. Furthermore, we found that richness and community composition of fungi are shaped primarily by abiotic factors and to a lesser, though still significant extent, by floristic composition. Along this mesotopographic gradient, environmental severity is strongly correlated with richness in all fungal functional groups: positively in saprotrophic, pathogenic and lichenised fungi, and negatively in ectomycorrhizal and root endophytic fungi. Our results suggest complex interactions amongst functional groups, possibly due to nutrient limitation or competitive exclusion, with potential implications on soil carbon stocks. These findings are important in the light of the environmental changes predicted for the Arctic.

Experimental soil warming shifts the fungal community composition at the alpine treeline

Increased CO₂ emissions and global warming may alter the composition of fungal communities through the removal of temperature limitation in the plant-soil system, faster nitrogen (N) cycling and changes in the carbon (C) allocation of host plants to the rhizosphere. At a Swiss treeline featuring Larix decidua and Pinus uncinata, the effects of multiple years of CO₂ enrichment and experimental soil warming on the fungal community composition in the organic horizons were analysed using 454-pyrosequencing of ITS2 amplicons. Sporocarp production and colonization of ectomycorrhizal root tips were investigated in parallel. Fungal community composition was significantly altered by soil warming, whereas CO₂ enrichment had little effect. Tree species influenced fungal community composition and the magnitude of the warming responses. The abundance of ectomycorrhizal fungal taxa was positively correlated with N availability, and ectomycorrhizal taxa specialized for conditions of high N availability proliferated with warming, corresponding to considerable increases in inorganic N in warmed soils. Traits related to N utilization are important in determining the responses of ectomycorrhizal fungi to warming in N-poor cold ecosystems. Shifts in the overall fungal community composition in response to higher temperatures may alter fungal-driven processes with potential feedbacks on ecosystem N cycling and C storage at the alpine treeline.

Does warming by open-top chambers induce change in the root-associated fungal community of the arctic dwarf shrub Cassiope tetragona (Ericaceae)?

Climate change may alter mycorrhizal communities, which impact ecosystem characteristics such as carbon sequestration processes. These impacts occur at a greater magnitude in Arctic ecosystems, where the climate is warming faster than in lower latitudes. Cassiope tetragona (L.) D. Don is an Arctic plant species in the Ericaceae family with a circumpolar range. C. tetragona has been reported to form ericoid mycorrhizal (ErM) as well as ectomycorrhizal (ECM) symbioses. In this study, the fungal taxa present within roots of C. tetragona plants collected from Svalbard were investigated using DNA metabarcoding. In light of ongoing climate change in the Arctic, the effects of artificial warming by open-top chambers (OTCs) on the fungal root community of C. tetragona were evaluated. We detected only a weak effect of warming by OTCs on the root-associated fungal communities that was masked by the spatial variation between sampling sites. The root fungal community of C. tetragona was dominated by fungal groups in the Basidiomycota traditionally classified as either saprotrophic or ECM symbionts, including the orders Sebacinales and Agaricales and the genera Clavaria, Cortinarius, and Mycena. Only a minor proportion of the operational taxonomic units (OTUs) could be annotated as ErM-forming fungi. This indicates that C. tetragona may be forming mycorrhizal symbioses with typically ECM-forming fungi, although no characteristic ECM root tips were observed. Previous studies have indicated that some saprophytic fungi may also be involved in biotrophic associations, but whether the saprotrophic fungi in the roots of C. tetragona are involved in biotrophic associations remains unclear. The need for more experimental and microscopy-based studies to reveal the nature of the fungal associations in C. tetragona roots is emphasized.

Changes in richness and community composition of ectomycorrhizal fungi among altitudinal vegetation types on Mount Kinabalu in Borneo

The distribution patterns of tropical ectomycorrhizal (ECM) fungi along altitudinal gradients remain largely unknown. Furthermore, despite being an iconic site for biodiversity research, virtually nothing is known about the diversity and spatial patterns of fungi on Mt Kinabalu and neighbouring mountain ranges. We carried out deep DNA sequencing of soil samples collected between 425 and 4000 m above sea level to compare richness and community composition of ECM fungi among altitudinal forest types in Borneo. In addition, we tested whether the observed patterns are driven by habitat or by geometric effect of overlapping ranges of species (mid-domain effect). Community composition of ECM fungi was strongly correlated with elevation. In most genera, richness peaked in the mid-elevation montane forest zone, with the exception of tomentelloid fungi, which showed monotonal decrease in richness with increasing altitude. Richness in lower-mid- and mid-elevations was significantly greater than predicted under the mid-domain effect model. We provide the first insight into the composition of ECM fungal communities and their strong altitudinal turnover in Borneo. The high richness and restricted distribution of many ECM fungi in the montane forests suggest that mid-elevation peak richness is primarily driven by environmental characteristics of this habitat and not by the mid-domain effect.

Ectomycorrhizal fungal response to warming is linked to poor host performance at the boreal-temperate ecotone

Rising temperatures associated with climate change have been shown to negatively affect the photosynthetic rates of boreal forest tree saplings at their southern range limits. To quantify the responses of ectomycorrhizal (EM) fungal communities associated with poorly performing hosts, we sampled the roots of Betula papyrifera and Abies balsamea saplings growing in the B4Warmed (Boreal Forest Warming at an Ecotone in Danger) experiment. EM fungi on the root systems of both hosts were compared from ambient and +3.4 °C air and soil warmed plots at two sites in northern Minnesota. EM fungal communities were assessed with high-throughput sequencing along with measures of plant photosynthesis, soil temperature, moisture, and nitrogen. Warming selectively altered EM fungal community composition at both the phylum and genus levels, but had no significant effect on EM fungal operational taxonomic unit (OTU) diversity. Notably, warming strongly favored EM Ascomycetes and EM fungi with short-contact hyphal exploration types. Declining host photosynthetic rates were also significantly inversely correlated with EM Ascomycete and EM short-contact exploration type abundance, which may reflect a shift to less carbon demanding fungi due to lower photosynthetic capacity. Given the variation in EM host responses to warming, both within and between ecosystems, better understanding the link between host performance and EM fungal community structure will to clarify how climate change effects cascade belowground.

Experimental Climate Change Modifies Degradative Succession in Boreal Peatland Fungal Communities

Peatlands play an important role in global climate change through sequestration of atmospheric CO₂. Climate-driven changes in the structure of fungal communities in boreal peatlands that favor saprotrophic fungi can substantially impact carbon dynamics and nutrient cycling in these crucial ecosystems. In a mesocosm study using a full factorial design, 100 intact peat monoliths, complete with living Sphagnum and above-ground vascular vegetation, were subjected to three climate change variables (increased temperature, reduced water table, and elevated CO₂ concentrations). Peat litterbags were placed in mesocosms, and fungal communities in litterbags were monitored over 12 months to assess the impacts of climate change variables on peat-inhabiting fungi. Changes in fungal richness, diversity, and community composition were assessed using Illumina MiSeq sequencing of ribosomal DNA (rDNA). While general fungal richness reduced under warming conditions, Ascomycota exhibited higher diversity under increased temperature treatments over the course of the experiment. Both increased temperature and lowered water table position drove shifts in fungal community composition with a strong positive effect on endophytic and mycorrhizal fungi (including one operational taxonomic unit (OTU) tentatively identified as Barrenia panicia) and different groups of saprotrophs identified as Mortierella, Galerina, and Mycena. These shifts were observed during a predicted degradative succession in the decomposer community as different carbon substrates became available. Since fungi play a central role in peatland communities, increased abundances of saprotrophic fungi under warming conditions, at the expense of reduced fungal richness overall, may increase decomposition rates under future climate scenarios and could potentially aggravate the impacts of climate change.

Enhanced summer warming reduces fungal decomposer diversity and litter mass loss more strongly in dry than in wet tundra

Many Arctic regions are currently experiencing substantial summer and winter climate changes. Litter decomposition is a fundamental component of ecosystem carbon and nutrient cycles, with fungi being among the primary decomposers. To assess the impacts of seasonal climatic changes on litter fungal communities and their functioning, Betula glandulosa leaf litter was surface-incubated in two adjacent low Arctic sites with contrasting soil moisture regimes: dry shrub heath and wet sedge tundra at Disko Island, Greenland. At both sites, we investigated the impacts of factorial combinations of enhanced summer warming (using open-top chambers; OTCs) and deepened snow (using snow fences) on surface litter mass loss, chemistry and fungal decomposer communities after approximately 1 year. Enhanced summer warming significantly restricted litter mass loss by 32% in the dry and 17% in the wet site. Litter moisture content was significantly reduced by summer warming in the dry, but not in the wet site. Likewise, fungal total abundance and diversity were reduced by OTC warming at the dry site, while comparatively modest warming effects were observed in the wet site. These results suggest that increased evapotranspiration in the OTC plots lowered litter moisture content to the point where fungal decomposition activities became inhibited. In contrast, snow addition enhanced fungal abundance in both sites but did not significantly affect litter mass loss rates. Across sites, control plots only shared 15% of their fungal phylotypes, suggesting strong local controls on fungal decomposer community composition. Nevertheless, fungal community functioning (litter decomposition) was negatively affected by warming in both sites. We conclude that although buried soil organic matter decomposition is widely expected to increase with future summer warming, surface litter decay and nutrient turnover rates in both xeric and relatively moist tundra are likely to be significantly restricted by the evaporative drying associated with warmer air temperatures.

Long-term increase in snow depth leads to compositional changes in arctic ectomycorrhizal fungal communities

Many arctic ecological processes are regulated by soil temperature that is tightly interconnected with snow cover distribution and persistence. Recently, various climate-induced changes have been observed in arctic tundra ecosystems, e.g. shrub expansion, resulting in reduction in albedo and greater C fixation in aboveground vegetation as well as increased rates of soil C mobilization by microbes. Importantly, the net effects of these shifts are unknown, in part because our understanding of belowground processes is limited. Here, we focus on the effects of increased snow depth, and as a consequence, increased winter soil temperature on ectomycorrhizal (ECM) fungal communities in dry and moist tundra. We analyzed deep DNA sequence data from soil samples taken at a long-term snow fence experiment in Northern Alaska. Our results indicate that, in contrast with previously observed responses of plants to increased snow depth at the same experimental site, the ECM fungal community of the dry tundra was more affected by deeper snow than the moist tundra community. In the dry tundra, both community richness and composition were significantly altered while in the moist tundra, only community composition changed significantly while richness did not. We observed a decrease in richness of Tomentella, Inocybe and other taxa adapted to scavenge the soil for labile N forms. On the other hand, richness of Cortinarius, and species with the ability to scavenge the soil for recalcitrant N forms, did not change. We further link ECM fungal traits with C soil pools. If future warmer atmospheric conditions lead to greater winter snow fall, changes in the ECM fungal community will likely influence C emissions and C fixation through altering N plant availability, fungal biomass and soil-plant C-N dynamics, ultimately determining important future interactions between the tundra biosphere and atmosphere.

Ectomycorrhizal and saprotrophic fungi respond differently to long-term experimentally increased snow depth in the High Arctic

Changing climate is expected to alter precipitation patterns in the Arctic, with consequences for subsurface temperature and moisture conditions, community structure, and nutrient mobilization through microbial belowground processes. Here, we address the effect of increased snow depth on the variation in species richness and community structure of ectomycorrhizal (ECM) and saprotrophic fungi. Soil samples were collected weekly from mid‐July to mid‐September in both control and deep snow plots. Richness of ECM fungi was lower, while saprotrophic fungi was higher in increased snow depth plots relative to controls. [Correction added on 23 September 2016 after first online publication: In the preceding sentence, the richness of ECM and saprotrophic fungi were wrongly interchanged and have been fixed in this current version.] ECM fungal richness was related to soil NO₃‐N, NH₄‐N, and K; and saprotrophic fungi to NO₃‐N and pH. Small but significant changes in the composition of saprotrophic fungi could be attributed to snow treatment and sampling time, but not so for the ECM fungi. Delayed snow melt did not influence the temporal variation in fungal communities between the treatments. Results suggest that some fungal species are favored, while others are disfavored resulting in their local extinction due to long‐term changes in snow amount. Shifts in species composition of fungal functional groups are likely to affect nutrient cycling, ecosystem respiration, and stored permafrost carbon.

Molecular inference, multivariate morphometrics and ecological assessment are applied in concert to delimit species in the Russula clavipes complex

Species of Russula subsect. Xerampelinae are notoriously difficult to identify and name and have not been subject to molecular study. A group of species, referred to here as the R. clavipes complex, growing in association with Salix, Betula and Populus as well as coniferous tree species from temperate to arctic and alpine habitats, were examined. Analyses of the nuc rDNA internal transcribed spacer (ITS) region and a numerical analysis of morphological characters were used. The R. clavipes complex is a monophyletic group within Russula subsect. Xerampelinae, according to molecular results. The complex includes three species: R. nuoljae is a phylogenetically and morphologically well-supported species while the other two, R. clavipes and R. pascua, are similar based on ITS data and morphology but separate based on their ecology. Russula pseudoolivascens is conspecific with R. clavipes Several combinations of characters traditionally used in the taxonomy of R. subsect. Xerampelinae are inappropriate for species delimitation in this group and the adequacy of the ITS for species identification in this group is discussed. Detailed microscopic observations on the type collection of R. nuoljae are presented and illustrated, along with a key to the European members of R. subsect. Xerampelinae.

Root-associated fungi of Vaccinium carlesii in subtropical forests of China: intra- and inter-annual variability and impacts of human disturbances

Ericoid mycorrhiza (ERM) are expected to facilitate establishment of ericaceous plants in harsh habitats. However, diversity and driving factors of the root-associated fungi of ericaceous plants are poorly understood. In this study, hair-root samples of Vaccinium carlesii were taken from four forest types: old growth forests (OGF), secondary forests with once or twice cutting (SEC I and SEC II), and Cunninghamia lanceolata plantation (PLF). Fungal communities were determined using high-throughput sequencing, and impacts of human disturbances and the intra- and inter-annual variability of root-associated fungal community were evaluated. Diverse fungal taxa were observed and our results showed that (1) Intra- and inter-annual changes in root-associated fungal community were found, and the Basidiomycota to Ascomycota ratio was related to mean temperature of the sampling month; (2) Human disturbances significantly affected structure of root-associated fungal community of V. carlesii, and two secondary forest types were similar in root-associated fungal community and were closer to that of the old growth forest; (3) Plant community composition, edaphic parameters, and geographic factors significantly affected root-associated fungal communities of V. carlesii. These results may be helpful in better understanding the maintenance mechanisms of fungal diversity associated with hair roots of ERM plants under human disturbances.

Microbial diversity and functional capacity in polar soils

Global change is disproportionately affecting cold environments (polar and high elevation regions), with potentially negative impacts on microbial diversity and functional processes. In most cold environments the combination of low temperatures, and physical stressors, such as katabatic wind episodes and limited water availability result in biotic systems, which are in trophic terms very simple and primarily driven by microbial communities. Metagenomic approaches have provided key insights on microbial communities in these systems and how they may adapt to stressors and contribute towards mediating crucial biogeochemical cycles. Here we review, the current knowledge regarding edaphic-based microbial diversity and functional processes in Antarctica, and the Artic. Such insights are crucial and help to establish a baseline for understanding the impact of climate change on Polar Regions.

Effects of warming on ectomycorrhizal colonization and nitrogen nutrition of Picea asperata seedlings grown in two contrasting forest ecosystems

Ectomycorrhiza (ECM) plays an important role in plant nitrogen (N) nutrition and regulates plant responded to climate warming. We conducted a field experiment in a natural forest and a plantation in the eastern Tibetan Plateau to estimate the warming effects of open-top chambers (OTC) on ECM and N nutrition of Picea asperata seedlings. Four-year warming significantly decreased ECM colonization, ECM fungal biomass, fine root vigor, and the N concentration of leaf, stem and coarse root, but significantly increased fine root N concentration and N content of leaf, stem, fine root and whole plant in natural forest. Contrarily, warming induced no obvious change in most of these parameters in plantation. Moreover, warming decreased rhizospheric soil inorganic N content in both forests. Our results showed that four-year warming was not beneficial for ECM colonization of P. asperata seedlings in the two forests, and the seedlings in natural forest were more sensitive and flexible to experimental warming than in plantation. The changes of ECM colonization and fine root biomass for effective N uptake would be good for plant growth and remit N leaching under future warming in natural forest.

Long-term warming alters richness and composition of taxonomic and functional groups of arctic fungi

Fungi, including symbionts, pathogens and decomposers, play crucial roles in community dynamics and nutrient cycling in terrestrial ecosystems. Despite their ecological importance, the response of most arctic fungi to climate warming is unknown, so are their potential roles in driving the observed and predicted changes in tundra communities. We carried out deep DNA sequencing of soil samples to study the long-term effects of experimental warming on fungal communities in dry heath and moist tussock tundra in Arctic Alaska. The data presented here indicate that fungal community composition responds strongly to warming in the moist tundra, but not in the dry tundra. While total fungal richness was not significantly affected by warming, there were clear correlations among operational taxonomic unit richness of various ecological and taxonomic groups and long-term warming. Richness of ectomycorrhizal, ericoid mycorrhizal and lichenized fungi generally decreased with warming, while richness of saprotrophic, plant and animal pathogenic, and root endophytic fungi tended to increase in the warmed plots. More importantly, various taxa within these functional guilds followed opposing trends that highlight the importance of species-specific responses to warming. We recommend that species-level ecological differences be taken into account in climate change and nutrient cycling studies that involve arctic fungi.