Temporal turnover of the soil microbiome composition is guild-specific.

Although spatial and temporal variation are both important components structuring microbial communities, the exact quantification of temporal turnover rates of fungi and bacteria has not been performed to date. In this study, we utilised repeated resampling of bacterial and fungal communities at specific locations across multiple years to describe their patterns and rates of temporal turnover. Our results show that microbial communities undergo temporal change at a rate of 0.010-0.025 per year (in units of Sorensen similarity), and the change in soil is slightly faster in fungi than in bacteria, with bacterial communities changing more rapidly in litter than soil. Importantly, temporal development differs across fungal guilds and bacterial phyla with different ecologies. While some microbial guilds show consistent responses across regional locations, others show site-specific development with weak general patterns. These results indicate that guild-level resolution is important for understanding microbial community assembly, dynamics and responses to environmental factors.

Distinct phylogeographic structure recognized within Desmazierella acicola.

Desmazierella acicola (anamorph Verticicladium trifidum, Chorioactidaceae) represents a frequent colonizer of pine needles in litter. Considering the global diversity and distribution of pine species, we expected different phylogenetic lineages to exist in different geographical and climatic areas inhabited by these hosts. We compared DNA sequence data with phenotypic characteristics (morphology of the anamorph and growth at three different temperatures) of 43 strains isolated mostly from pine and also spruce needle litter sampled in various geographical areas. Analyses of ITS rDNA recovered eight geographically structured lineages. Fragments of genes for the translation elongation factor 1-α, and the second largest subunit of RNA polymerase II reproduced similar lineages, although not all of them were monophyletic. The similarity in ITS sequences among the clade with samples from Continental-Atlantic Europe and four other clades was lower than 95%. Several lineages exhibit also a tendency toward host specificity to a particular pine species. Growth tests at different temperatures indicated a different tolerance to specific climatic conditions in different geographic areas. However, the surveyed phenotypic characteristics also showed high variation within lineages, most evident in the morphology of the anamorph. Until a morphological study of the teleomorph is carried out, all of these lineages should be treated as distinct populations within a single species.

Climate-driven shifts in plant and fungal communities can lead to topsoil carbon loss in alpine ecosystems.

Alpine tundra ecosystems suffer from ongoing warming-induced tree encroachment and vegetation shifts. While the effects of tree line expansion on the alpine ecosystem receive a lot of attention, there is also an urgent need for understanding the effect of climate change on shifts within alpine vegetation itself, and how these shifts will consequently affect soil microorganisms and related ecosystem characteristics such as carbon storage. For this purpose, we explored relationships between climate, soil chemistry, vegetation, and fungal communities across seven mountain ranges at 16 alpine tundra locations in Europe. Among environmental factors, our data highlighted that plant community composition had the most important influence on variation in fungal community composition when considered in combination with other factors, while climatic factors had the most important influence solely. According to our results, we suggest that rising temperature, associated with a replacement of ericoid-dominated alpine vegetation by non-mycorrhizal or arbuscular mycorrhizal herbs and grasses, will induce profound changes in fungal communities toward higher dominance of saprotrophic and arbuscular mycorrhizal fungi at the expense of fungal root endophytes. Consequently, topsoil fungal biomass and carbon content will decrease.

Bacterial community in soil and tree roots of Picea abies shows little response to clearcutting.

Clearcutting represents a standard management practice in temperate forests with dramatic consequences for the forest ecosystem. The removal of trees responsible for the bulk of primary production can result in a complex response of the soil microbiome. While studies have shown that tree root-symbiotic ectomycorrhizal fungi disappear from soil and decomposing fine roots of trees become a hotspot for fungal decomposition, the fate of the bacterial component of the soil microbiome following clearcutting is unclear. Here, we investigated the response of bacterial community composition for 2 years following clearcutting of a Picea abies stand in soil, rhizosphere and tree roots, by 16S rRNA amplicon sequencing. While in the first few months after clearcutting there was no significant response of bacterial community composition in the rhizosphere and soil, bacterial communities associated with tree roots underwent more profound changes over time. Acidobacteria were abundant in rhizosphere and soil, while Firmicutes were strongly represented in the roots. In addition, bacterial communities on decomposing roots were significantly different from those on pre-clearcut live roots. Compared with fungi, the response of bacterial communities to clearcutting was much less pronounced, indicating independent development of the two microbial domains.

Functional soil mycobiome across ecosystems.

Fungi support a wide range of ecosystem processes such as decomposition of organic matter and plant-soil relationships. Yet, our understanding of the factors driving the metaproteome of fungal communities is still scarce. Here, we conducted a field survey including data on fungal biomass (by phospholipid fatty acids, PLFA), community composition (by metabarcoding of the 18S rRNA gene from extracted DNA) and functional profile (by metaproteomics) to investigate soil fungi and their relation to edaphic and environmental variables across three ecosystems (forests, grasslands, and shrublands) distributed across the globe. We found that protein richness of soil fungi was significantly higher in forests than in shrublands. Among a wide suite of edaphic and environmental variables, we found that soil carbon content and plant cover shaped evenness and diversity of fungal soil proteins while protein richness correlated to mean annual temperature and pH. Functions shifted from metabolism in forests to information processing and storage in shrublands. The differences between the biomes highlight the utility of metaproteomics to investigate functional microbiomes in soil. SIGNIFICANCE: Understanding the structure and the function of fungal communities and the driving factors is crucial to determine the contribution to ecosystem services of fungi and what effect future climate has. While there is considerable knowledge on the ecosystem processes provided by fungi such as decomposition of organic matter and plant-soil relationships, our understanding of the driving factors of the fungal metaproteome is scarce. Here we present the first estimates of fungal topsoil protein diversity in a wide range of soils across global biomes. We report taxonomic differences for genes delivered by amplicon sequencing of the 18S rRNA gene and differences of the functional microbiome based on metaproteomics. Both methods gave a complementary view on the fungal topsoil communities, unveiling both taxonomic and functional changes with changing environments. Such a comprehensive multi-omic analysis of fungal topsoil communities has never been performed before, to our knowledge.

Author Correction: GlobalFungi, a global database of fungal occurrences from high-throughput-sequencing metabarcoding studies.

An amendment to this paper has been published and can be accessed via a link at the top of the paper.

GlobalFungi, a global database of fungal occurrences from high-throughput-sequencing metabarcoding studies.

Fungi are key players in vital ecosystem services, spanning carbon cycling, decomposition, symbiotic associations with cultivated and wild plants and pathogenicity. The high importance of fungi in ecosystem processes contrasts with the incompleteness of our understanding of the patterns of fungal biogeography and the environmental factors that drive those patterns. To reduce this gap of knowledge, we collected and validated data published on the composition of soil fungal communities in terrestrial environments including soil and plant-associated habitats and made them publicly accessible through a user interface at https://globalfungi.com . The GlobalFungi database contains over 600 million observations of fungal sequences across > 17 000 samples with geographical locations and additional metadata contained in 178 original studies with millions of unique nucleotide sequences (sequence variants) of the fungal internal transcribed spacers (ITS) 1 and 2 representing fungal species and genera. The study represents the most comprehensive atlas of global fungal distribution, and it is framed in such a way that third-party data addition is possible.

Root-Associated Fungal Communities From Two Phenologically Contrasting Silver Fir (Abies alba Mill.) Groups of Trees.

Root-associated fungal communities are important components in ecosystem processes, impacting plant growth and vigor by influencing the quality, direction, and flow of nutrients and water between plants and fungi. Linkages of plant phenological characteristics with belowground root-associated fungal communities have rarely been investigated, and thus our aim was to search for an interplay between contrasting phenology of host ectomycorrhizal trees from the same location and root-associated fungal communities (ectomycorrhizal, endophytic, saprotrophic and pathogenic root-associated fungi) in young and in adult silver fir trees. The study was performed in a managed silver fir forest site. Twenty-four soil samples collected under two phenologically contrasting silver fir groups were analyzed for differences in root-associated fungal communities using Illumina sequencing of a total root-associated fungal community. Significant differences in beta diversity and in mean alpha diversity were confirmed for overall community of ectomycorrhizal root-associated fungi, whereas for ecologically different non-ectomycorrhizal root-associated fungal communities the differences were significant only for beta diversity and not for mean alpha diversity. At genus level root-associated fungal communities differed significantly between early and late flushing young and adult silver fir trees. We discuss the interactions through which the phenology of host plants either drives or is driven by the root-associated fungal communities in conditions of a sustainably co-naturally managed silver fir forest.

A meta-analysis of global fungal distribution reveals climate-driven patterns.

The evolutionary and environmental factors that shape fungal biogeography are incompletely understood. Here, we assemble a large dataset consisting of previously generated mycobiome data linked to specific geographical locations across the world. We use this dataset to describe the distribution of fungal taxa and to look for correlations with different environmental factors such as climate, soil and vegetation variables. Our meta-study identifies climate as an important driver of different aspects of fungal biogeography, including the global distribution of common fungi as well as the composition and diversity of fungal communities. In our analysis, fungal diversity is concentrated at high latitudes, in contrast with the opposite pattern previously shown for plants and other organisms. Mycorrhizal fungi appear to have narrower climatic tolerances than pathogenic fungi. We speculate that climate change could affect ecosystem functioning because of the narrow climatic tolerances of key fungal taxa.