Diversity and community structure of ectomycorrhizal fungi associated with Larix chinensis across the alpine treeline ecotone of Taibai Mountain

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.

Four New Species of Tomentella (Thelephorales, Basidiomycota) from Subtropical Forests in Southwestern China

Species of the basidiomycetous genus Tomentella are widely distributed throughout temperate forests. Numerous studies on the taxonomy and phylogeny of Tomentella have been conducted from the temperate zone in the Northern hemisphere, but few have been from subtropical forests. In this study, four new species, T. casiae, T. guiyangensis, T. olivaceomarginata and T. rotundata from the subtropical mixed forests of Southwestern China, are described and illustrated based on morphological characteristics and phylogenetic analyses of the internal transcribed spacer regions (ITS) and the large subunit of the nuclear ribosomal RNA gene (LSU). Molecular analyses using Maximum Likelihood and Bayesian analysis confirmed the phylogenetic positions of these four new species. Anatomical comparisons among the closely related species in phylogenetic and morphological features are discussed. Four new species could be distinguished by the characteristics of basidiocarps, the color of the hymenophoral surface, the size of the basidia, the shape of the basidiospores and some other features.

Ectomycorrhizal communities of adult and young European larch are diverse and dynamics at high altitudinal sites

Background/Aims

The European larch is a pioneer tree and a valuable economic resource in subalpine ecosystems, thus playing crucial roles to ecosystem services and human activities. However, their ectomycorrhizal fungal community remains unknown in high altitudinal natural habitats. Here, we explore the mycobiont diversity of Larix decidua var. decidua between naturally rejuvenated and adult trees, compare ectomycorrhizal colonization patterns in geographically disjunct areas within the Alps of South Tyrol, Italy, characterized by distinct climatic conditions, and explore turnover rates across various seasons.

Methods

Our approach combines morphotyping of mycorrhized root tips with molecular analysis. Particular effort was given to monitor both ectomycorrhizal host-specialist and -generalist fungi.

Results

Both adult and young trees show a 100% mycorrhization rate, with a total diversity of 68 ectomycorrhizal species. The ectomycorrhizal composition is dominated by typical host specialists of larch trees (e.g., Lactarius porninsis, Russula laricina, Suillus cavipes, S. grevillei, S. viscidus), which are widely distributed across sites. A rich diversity of host generalists was also detected. The composition of rare species within a habitat was comparatively consistent during one sampling campaign, but exhibited significant differences among individual sampling campaigns. The ectomycorrhizal compositions were only weakly correlated with distinct climatic conditions and tree ages. However, species richness and diversity, particularly of generalist fungi, was consistently higher in warmer, drier sites compared to cooler, more humid ones.

Conclusions

This study suggests potential mycobiont community shifts across climatic conditions with significant implications for the adaptability and resilience of subalpine forests in the face of climate change.

Supplementary Information

The online version contains supplementary material available at 10.1007/s11104-024-06721-8.

Effects of Male and Female Strains of Salix linearistipularis on Physicochemical Properties and Microbial Community Structure in Saline-Alkali Soil

The woody plant gender difference may lead to alteration in rhizosphere microbial communities and soil physicochemical properties. In this study, we investigated the differences in rhizosphere soil properties and microbial community structures of S. linearistipularis. Rhizosphere microorganisms were analyzed by high-throughput sequencing technology. The results showed that there were significant differences in rhizosphere soil nutrition between male and female S. linearistipularis plants in saline-alkali soil. The female S. linearistipularis plants significantly reduce soil pH values and significantly increase the soil water content (SWC), available total nitrogen (TN), soil organic matter (SOM), and soil urease activity (S-UE) compared to the male plant. The ACE, Chao, and Shannon index of the female plant was significantly higher than that of the male strain. At the level of Bacteriophyta, the relative abundance of Actinobacteriota in male and female S. linearistipularis was the highest, with 34.26% and 31.03%, respectively. Among the named bacterial genera, the relative abundance of Defluviicoccus of male and female plants was the highest, with 2.67% and 5.27%, respectively. At the level of Eumycophyta, the relative abundance of Ascomycetes in male and female plants was the highest, with 54.93% and 52.10%, respectively. Among the named fungi genera, the relative abundance of male and female plants of Mortierella was the highest, with 6.18% and 9.31%, respectively. In addition, soil pH, SOM, SWC, and S-UE activities were the main driving factors of soil microbial community structures. In the process of restoring saline-alkali land in the Songnen Plain, we may prioritise the planting of female S. linearistipularis, which also provides a theoretical basis for the microorganisms restoration of saline-alkali land in the Songnen plain.

Soil Fungal Community Characteristics at Timberlines of Sejila Mountain in Southeast Tibet, China

Soil fungal community characteristics of alpine timberlines are unclear. In this study, soil fungal communities in five vegetation zones across timberlines on the south and north slopes of Sejila Mountain in Tibet, China were investigated. The results show that the alpha diversity of soil fungi was not different between the north- and south-facing timberlines or among the five vegetation zones. Archaeorhizomyces (Ascomycota) was a dominant genus at the south-facing timberline, whereas the ectomycorrhizal genus Russula (Basidiomycota) decreased with decreasing Abies georgei coverage and density at the north-facing timberline. Saprotrophic soil fungi were dominant, but their relative abundance changed little among the vegetation zones at the south timberline, whereas ectomycorrhizal fungi decreased with tree hosts at the north timberline. Soil fungal community characteristics were related to coverage and density, soil pH and ammonium nitrogen at the north timberline, whereas they had no associations with the vegetation and soil factors at the south timberline. In conclusion, timberline and A. georgei presence exerted apparent influences on the soil fungal community structure and function in this study. The findings may enhance our understanding of the distribution of soil fungal communities at the timberlines of Sejila Mountain.

A Closer Examination of the 'Abundant-Center' for Ectomycorrhizal Fungal Community Associated With Picea crassifolia in China

A long-standing hypothesis in biogeography predicts that a species' abundance is highest at the center of its geographical range and decreases toward its edges. In this study, we test the abundant-center hypothesis of ectomycorrhizal (ECM) fungal communities associated with Picea crassifolia, an endemic species widely distributed in northwest China. We analyzed the taxonomic richness and the relative abundance of ECM fungi in four main distribution areas, from center to edges. In total, 234 species of ECM fungi were detected, and of these, 137 species were shared among all four sites. Inocybe, Sebacina, Tomentella, and Cortinarius were the dominant genera. ECM fungal richness and biodiversity were highest at the central and lower at peripheral sites. Our results indicated that ECM fungal species richness was consistent with the abundant-center hypothesis, while the relative abundances of individual fungal genera shifted inconsistently across the plant's range.

Composition and Functional Characteristics and Influencing Factors of Bacterioplankton Community in the Huangshui River, China

Bacterial community plays a key role in environmental and ecological processes of river ecosystems. Given the special climatic and geographical conditions, studying the compositional characteristics of microorganisms in highland rivers and the relationship between such microorganisms and water physicochemical factors is important for an in-depth understanding of microbial ecological mechanisms. In the present study, high-throughput sequencing was used to investigate and study the bacterioplankton community of the Huangshui River in the ecotone zone of the Qinghai Plateau and Loess Plateau. The results showed that the Huangshui River had significantly lower alpha diversity than the plain rivers. Despite the similarity in their environmental conditions, the main taxonomic compositions of the bacterial communities were distinct between the Huangshui River and polar regions (the Arctic and Antarctica). Proteobacteria accounted for the largest proportion (30.79–99.98%) of all the sequences, followed by Firmicutes (0–49.38%). Acidiphilium was the most numerous genera, which accounted for 0.03–86.16% of the assigned 16S reads, followed by Acidocella (0–95.9%), both belonging to Alphaproteobacteria. The diverse taxa of potential pathogens, such as Acinetobacter, Pseudomonas, and Aeromonas, were also identified. A principal coordinates analysis, coupled with a canonical correspondence analysis, showed spatial variations in the bacterial community composition. The water physical properties (e.g., Cr⁶⁺, total phosphorus, and COD_Mn); altitude; and land use (e.g., urban land cover and aquaculture) determined the distribution of the bacterioplankton composition. PICRUSt2 revealed that the overall functional profiles of the bacterial communities in different samples were similar, and our results suggested the potential health risks of water sources in this area. This work provided valuable insight into the composition of the plankton bacterial community and its relationship with the environmental factors in the Huangshui River in the ecotone zone of the Qinghai Plateau and Loess Plateau and a theoretical foundation for ecological health management.

Diversity of Ectomycorrhizal Fungal Communities in Four Types of Stands in Pinus massoniana Plantation in the West of China

Ectomycorrhizal (ECM) fungi can form symbioses with plant roots, which play an important role in regulating the rhizosphere microenvironment. As a broad-spectrum ECM tree species, Pinus massoniana forms symbiotic relationship called mycorrhiza with various ECM fungal species. In this study, four types of forests were selected from a 38-year-old Pinus plantation in eastern Sichuan, namely, pure P. massoniana forest (MC), P. massoniana mixed with Cunninghamia lanceolata forest (MS), P. massoniana–Cryptomeria fortunei forest (ML), and P. massoniana–broadleaved forest (MK), the species mixture ratio of all forests was 1:1. The ITS2 segment of ECM root tip sequenced by high-throughput sequencing using the Illumina MiSeq sequencing platform. (1) The ECM fungi of these four P. massoniana forests showed similar dominant genera but different relative abundances in community structure during the three seasons. (2) The alpha diversity index of ECM fungi was significantly influenced by season and forest type. (3) Soil pH, soil organic matter (SOM), total nitrogen (TN), C/N ratio, and total phosphorus (TP) influenced the ECM fungal community structure in different seasons. In summary, there were significant differences in ECM fungal communities among different forest types and different seasons; the colonization rate of ECM fungal in P. massoniana–Cunninghamia lanceolata was the highest, so we infer that Cunninghamia lanceolata is the most suitable tree species for mixed with P. massoniana in three mixture forests.

Saprotrophic fungal diversity predicts ectomycorrhizal fungal diversity along the timberline in the framework of island biogeography theory

Island biogeography theory (IBT) is one of the most fruitful paradigms in macroecology, positing positive species-area and negative species-isolation relationships for the distribution of organisms. Biotic interactions are also crucial for diversity maintenance on islands. In the context of a timberline tree species (Betula ermanii) as "virtual island", we surveyed ectomycorrhizal (EcM) fungal diversity along a 430-m vertical gradient on the top of Changbai Mountain, China, sampling fine roots and neighboring soils of B. ermanii. Besides elevation, soil properties and plant functional traits, endophytic and saprotrophic fungal diversity were assessed as candidate predictors to construct integrative models. EcM fungal diversity decreased with increasing elevation, and exhibited positive diversity to diameter at breast height and negative diversity to distance from forest edge relationships in both roots and soils. Integrative models further showed that saprotrophic fungal diversity was the strongest predictor of EcM fungal diversity, directly enhancing EcM fungal diversity in roots and soils. Our study supports IBT as a basic framework to explain EcM fungal diversity. The diversity-begets-diversity hypothesis within the fungal kingdom is more predictive for EcM fungal diversity within the IBT framework, which reveals a tight association between saprotrophic and EcM fungal lineages in the timberline ecosystem.

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.

Bacterial Diversity and Community Composition Distribution in Cold-Desert Habitats of Qinghai-Tibet Plateau, China

Bacterial communities in cold-desert habitats play an important ecological role. However, the variation in bacterial diversity and community composition of the cold-desert ecosystem in Qinghai–Tibet Plateau remains unknown. To fill this scientific gape, Illumina MiSeq sequencing was performed on 15 soil samples collected from different cold-desert habitats, including human-disturbed, vegetation coverage, desert land, and sand dune. The abundance-based coverage estimator, Shannon, and Chao indices showed that the bacterial diversity and abundance of the cold-desert were high. A significant variation reported in the bacterial diversity and community composition across the study area. Proteobacteria accounted for the largest proportion (12.4–55.7%) of all sequences, followed by Actinobacteria (9.2–39.7%), Bacteroidetes (1.8–21.5%), and Chloroflexi (2.7–12.6%). Furthermore, unclassified genera dominated in human-disturbed habitats. The community profiles of GeErMu, HongLiangHe, and CuoNaHu sites were different and metagenomic biomarkers were higher (22) in CuoNaHu sites. Among the soil physicochemical variables, the total nitrogen and electric conductivity significantly influenced the bacterial community structure. In conclusion, this study provides information regarding variation in diversity and composition of bacterial communities and elucidates the association between bacterial community structures and soil physicochemical variables in cold-desert habitats of Qinghai–Tibet Plateau.

The dominance of Suillus species in ectomycorrhizal fungal communities on Larix gmelinii in a post-fire forest in the Russian Far East

Wildfires can negatively affect ectomycorrhizal (EM) fungal communities. However, potential shifts in community structures due to wildfires have rarely been evaluated in the forests of eastern Eurasia, where surface fires are frequent. We investigated EM fungal communities in a Larix gmelinii-dominated forest that burned in 2003 in Zeya, in the Russian Far East. A total of 120 soil samples were collected from burned and adjacent unburned forest sites. The EM fungal root tips were morphotyped and internal transcribed spacer (ITS) sequences were obtained for fungal identification. We detected 147 EM fungal operational taxonomic units, and EM fungal richness was 25% lower at the burned site than at the unburned site. EM fungal composition was characterized by the occurrence of disturbance-adapted fungi (Amphinema and Wilcoxina) at the burned site and late-successional fungi (Lactarius, Russula and Cortinarius) at the unburned site. These findings suggest that the EM fungal communities did not recover to pre-fire levels 16 years after the fire. Suillus species were the dominant EM fungi on L. gmelinii, with greater richness and frequency at the burned site. Both Larix and Suillus exhibit adaptive traits to quickly colonize fire-disturbed habitats. Frequent surface fires common to eastern Eurasia are likely to play important roles in maintaining Larix forests, concomitantly with their closely associated EM fungi.

Ectomycorrhizal fungal communities in ice-age relict forests of Pinus pumila on nine mountains correspond to summer temperature

Ectomycorrhizal (ECM) fungi are critical symbionts of major forest trees, and their communities are affected by various environmental factors including temperature. However, previous knowledge concerning temperature effects does not exclude the effects of host species and coexisting plants, which usually change with temperature, and should be rigorously tested under the same vegetation type. Herein we examined ECM fungal communities in ice-age relict forests dominated by a single host species (Pinus pumila) distributed on nine mountains across >1000 km in Japan. Direct sequencing of rDNA ITS regions identified 154 ECM fungal species from 4134 ECM root-tip samples. Gradient analyses revealed a large contribution of temperature, especially summer temperature, to ECM fungal communities. Additionally, we explored global sequence records of each fungal species to infer its potential temperature niche, and used it to estimate the temperature of the observed communities. The estimated temperature was significantly correlated with the actual temperature of the research sites, especially in summer seasons, indicating inherent temperature niches of the fungal components could determine their distribution among the sites. These results indicate that temperature is still a significant determinant in structuring ECM fungal communities after excluding the effects of host species and coexisting plants. The results also imply that the rising temperature under global warming may have been affecting soil microbes unnoticeably, while such microbial community change may have been contributing to the resilience of the same vegetation.

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.

Ectomycorrhizal fungi may not act as a barrier inhibiting host plant absorption of heavy metals

Whether the huge external hyphal system of ectomycorrhizae that promotes host plants' acquisition of water and nutrients can selectively inhibit their transport of heavy metals at the same time remains unclear. In this experiment, we designed and conducted two types of soil-pot test to clarify the effects of EMF on the absorption and transport of copper (Cu) and cadmium (Cd) by host Pinus thunbergii seedlings. In the root-bag test, external hyphae took the initiative into the Cu/Cd-contaminated bulk soil, absorb and transport Cu and Cd to the rhizosphere soils and further transport it to the shoots of the host plants. Inoculation with EMF also promoted the uptake of nutrients by host plants, thereby increasing their biomass and improving Cu/Cd tolerance compared with non-inoculated plants. Inoculation with EMF species with higher Cu or Cd tolerance generated more phytostabilization and phytoextraction of Cu or Cd by host plants. In a short-term exposure test, inoculation with EMF accelerated the absorption of Cu and Cd by P. thunbergii within 12 h of Cu or Cd irrigation. Therefore, we concluded that EMF do not act as a barrier inhibiting the absorption of heavy metals by host plants, but rather promote this absorption. Improving the plant's nutritional status and promoting growth, diluting heavy metal concentrations, thereby reducing the toxic effects of heavy metals on host plants. These results provide the theoretical basis for the application of EMF in plant-microbial combinations for the phytostabilization and phytoextraction of heavy metal-contaminated soils.

Ectomycorrhizal fungal communities in alpine relict forests of Pinus pumila on Mt. Norikura, Japan

Ectomycorrhizal (ECM) symbioses are indispensable for the establishment of host trees, yet available information of ECM symbiosis in alpine forests is scarce. Pinus pumila is a typical ice age relict tree species in Japan and often forms monodominant dwarf vegetation above the tree line in mountains. We studied ECM fungi colonizing P. pumila on Mt. Norikura, Japan, with reference to host developmental stages, i.e., from current-year seedlings to mature trees. ECM fungal species were identified based on rDNA ITS sequences. Ninety-two ECM fungal species were confirmed from a total of 2480 root tips examined. Species in /suillus-rhizopogon and /wilcoxina were dominant in seedling roots. ECM fungal diversity increased with host development, due to the addition of species-rich fungal lineages (/cenococcum, /cortinarius, and /russula-lactarius) in late-successional stages. Such successional pattern of ECM fungi is similar to those in temperate pine systems, suggesting the predominant role of /suillus-rhizopogon in seedling establishment, even in relict alpine habitats fragmented and isolated for a geological time period. Most of the ECM fungi detected were also recorded in Europe or North America, indicating their potential Holarctic distribution and the possibility of their comigration with P. pumila through land bridges during ice ages. In addition, we found significant effects of soil properties on ECM fungal communities, which explained 34.1% of the total variation of the fungal communities. While alpine vegetation is regarded as vulnerable to the ongoing global warming, ECM fungal communities associated with P. pumila could be altered by the edaphic change induced by the warming.