Forest Age and Plant Species Composition Determine the Soil Fungal Community Composition in a Chinese Subtropical Forest

Fungal diversity and community composition are mainly related to soil and vegetation factors. However, the relative contribution of the different drivers remains largely unexplored, especially in subtropical forest ecosystems. We studied the fungal diversity and community composition of soils sampled from 12 comparative study plots representing three forest age classes (Young: 10–40 yrs; Medium: 40–80 yrs; Old: ≥80 yrs) in Gutianshan National Nature Reserve in South-eastern China. Soil fungal communities were assessed employing ITS rDNA pyrotag sequencing. Members of Basidiomycota and Ascomycota dominated the fungal community, with 22 putative ectomycorrhizal fungal families, where Russulaceae and Thelephoraceae were the most abundant taxa. Analysis of similarity showed that the fungal community composition significantly differed among the three forest age classes. Forest age class, elevation of the study plots, and soil organic carbon (SOC) were the most important factors shaping the fungal community composition. We found a significant correlation between plant and fungal communities at different taxonomic and functional group levels, including a strong relationship between ectomycorrhizal fungal and non-ectomycorrhizal plant communities. Our results suggest that in subtropical forests, plant species community composition is the main driver of the soil fungal diversity and community composition.     

EcM fungal community structure, but not diversity, altered in a Pb-contaminated shooting range in a boreal coniferous forest site in Southern Finland

Boreal forests contain diverse fungal communities that form essential ectomycorrhizal symbioses with trees. To determine the effects of lead (Pb) contamination on ectomycorrhizal fungal communities associated with the dominant pine (Pinus sylvestris L.), we surveyed sporocarps for 3 years, analyzed morphotyped ectomycorrhizal root tips by direct sequencing, and 454-sequenced fungal communities that grew into in-growth bags during a 2-year incubation at a shooting range where sectors vary in the Pb load. We recorded a total of 32 ectomycorrhizal fungi that formed conspicuous sporocarps, 27 ectomycorrhizal fungal phylotypes from 294 root tips, and 116 ectomycorrhizal fungal operation taxonomic unit (OTUs) from a total of 8194 internal transcribed spacer-2 454 sequences. Our ordination analyses by nonparametric multidimensional scaling (NMS) indicated that the Pb enrichment induced a shift in the ectomycorrhizal community composition. This was visible as indicative trends in the sporocarp and root tip data sets, but was explicitly clear in the communities observed in the in-growth bags. The compositional shift in the ectomycorrhizal community was mainly attributable to an increase in the frequencies of OTUs assigned to genus Thelephora and to a decrease in the OTUs assigned to Pseudotomentella, Suillus, and Tylospora in Pb-contaminated areas when compared with the control. While the compositional shifts are clear, their functional consequences for the dominant trees or soil ecosystem function remain undetermined.     

Diversity and community structure of ectomycorrhizal fungi in a wooded meadow

Wooded meadows are seminatural plant communities that support high diversity of various taxa. Due to changes in land use, wooded meadows have severely declined during the last century. The dominant trees in wooded meadows acquire mineral nutrients via ectomycorrhizal fungi. Using anatomotyping and sequencing of root tips, interpolation and extrapolation methods, we studied the diversity and community structure of ectomycorrhizal fungi in two soil horizons of both managed and forested parts of a wooded meadow in Estonia. Species of Thelephoraceae, Sebacinaceae and the genus Inocybe dominated the whole ectomycorrhizal fungal community of 172 observed species. Forested and managed parts of the wooded meadow harboured different communities of ectomycorrhizal fungi, whereas soil horizon had a negligible effect on the fungal community composition. Diverse soil conditions and host trees likely support the high richness of ectomycorrhizal fungi in the wooded meadow ecosystem. Direct sequencing integrated with interpolation and extrapolation methods are promising to identify the fungi at the species level and to compare species richness between communities of ectomycorrhizal fungi.     

Ectomycorrhizal-Dominated Boreal and Tropical Forests Have Distinct Fungal Communities,but Analogous Spatial Patterns across Soil Horizons

Fungi regulate key nutrient cycling processes in many forest ecosystems, but their diversity and distribution within and across ecosystems are poorly understood. Here, we examine the spatial distribution of fungi across a boreal and tropical ecosystem, focusing on ectomycorrhizal fungi. We analyzed fungal community composition across litter (organic horizons) and underlying soil horizons (0–20 cm) using 454 pyrosequencing and clone library sequencing. In both forests, we found significant clustering of fungal communities by site and soil horizons with analogous patterns detected by both sequencing technologies. Free-living saprotrophic fungi dominated the recently-shed leaf litter and ectomycorrhizal fungi dominated the underlying soil horizons. This vertical pattern of fungal segregation has also been found in temperate and European boreal forests, suggesting that these results apply broadly to ectomycorrhizal-dominated systems, including tropical rain forests. Since ectomycorrhizal and free-living saprotrophic fungi have different influences on soil carbon and nitrogen dynamics, information on the spatial distribution of these functional groups will improve our understanding of forest nutrient cycling.     

Structure and species composition of ectomycorrhizal fungal communities colonizing seedlings and adult trees of Pinus montezumae in Mexican neotropical forests

Mexico is a center of diversity for pines, but few studies have examined the ectomycorrhizal (ECM) fungal communities associated with pines in this country. We investigated the ECM communities associated with Pinus montezumae seedlings and mature trees in neotropical forests of central Mexico and compared their structure and species composition. Root tips were sampled on both planted seedlings and naturally occurring adult trees. A total of 42 ECM operational taxonomic units (OTUs) was found on P.?montezumae. Diversity and similarity indices showed that community structure was similar for both plant growth stages, but phylogenetic diversity and Chao-estimated richness were higher for seedlings. Species composition differed between communities. The dominant OTUs belonged to the families Atheliaceae, Cortinariaceae, and Sebacinaceae, although different taxa appeared to colonize seedlings and adults. Only 12 OTUs were shared between seedlings and adults, which suggests that ECM fungi which colonize seedlings are still not fully incorporated into mycelial networks and that ECM taxa colonizing young individuals of P.?montezumae are likely to come from fungal propagules. Intra-generic diversity could be an insurance mechanism to maintain forest productivity under stressed conditions. This is the first report describing the abundance of Atheliaceae in tree roots in neotropical ecosystems.     

Molecular Identification of Ectomycorrhizal Mycelium in Soil Horizons

Molecular identification techniques based on total DNA extraction provide a unique tool for identification of mycelium in soil. Using molecular identification techniques, the ectomycorrhizal (EM) fungal community under coniferous vegetation was analyzed. Soil samples were taken at different depths from four horizons of a podzol profile. A basidiomycete-specific primer pair (ITS1F-ITS4B) was used to amplify fungal internal transcribed spacer (ITS) sequences from total DNA extracts of the soil horizons. Amplified basidiomycete DNA was cloned and sequenced, and a selection of the obtained clones was analyzed phylogenetically. Based on sequence similarity, the fungal clone sequences were sorted into 25 different fungal groups, or operational taxonomic units (OTUs). Out of 25 basidiomycete OTUs, 7 OTUs showed high nucleotide homology (≥99%) with known EM fungal sequences and 16 were found exclusively in the mineral soil. The taxonomic positions of six OTUs remained unclear. OTU sequences were compared to sequences from morphotyped EM root tips collected from the same sites. Of the 25 OTUs, 10 OTUs had ≥98% sequence similarity with these EM root tip sequences. The present study demonstrates the use of molecular techniques to identify EM hyphae in various soil types. This approach differs from the conventional method of EM root tip identification and provides a novel approach to examine EM fungal communities in soil.     

Ectomycorrhizal fungal diversity in Quercus ilex Mediterranean woodlands: variation among sites and over soil depth profiles in hyphal exploration types, species richness and community composition

Understanding the factors underlying the distribution of biodiversity is a challenging issue in ecology. Here, we examined the distribution patterns of ectomycorrhizal fungal diversity across the soil profile in three Quercus ilex forests. Contact exploration type strongly dominated at all sites, but was most prevalent in the upper, organic-rich soil layers. At each site, three quarters of the ectomycorrhizal tips and 59 % of taxa were restricted to the ten first centimeters of the soil profile. The relative abundance of the dominant family Russulaceae increased with increasing soil depth. Species composition varied significantly among sites, with most species being rare. Species that occurred in only one of the three sites accounted for 78.9 % of all species, and 57.3 % of species were represented by a single ECM root tip. Our results suggest that (i) rare species at both local and regional scales contribute to the highly diverse fungal assemblages in Mediterranean forests and (ii) multi-sites studies including the whole soil profile are needed to provide comprehensive overviews of the taxonomic and functional diversities of ectomycorrhizal communities.     

Molecular phylogenetic biodiversity assessment of arctic and boreal ectomycorrhizal Lactarius Pers. (Russulales; Basidiomycota) in Alaska, based on soil and sporocarp DNA

Despite the critical roles fungi play in the functioning of ecosystems, especially as symbionts of plants and recyclers of organic matter, their biodiversity is poorly known in high-latitude regions. In this paper, we discuss the molecular diversity of one of the most diverse and abundant groups of ectomycorrhizal fungi: the genus Lactarius Pers. We analysed internal transcribed spacer rDNA sequences from both curated sporocarp collections and soil polymerase chain reaction clone libraries sampled in the arctic tundra and boreal forests of Alaska. Our genetic diversity assessment, based on various phylogenetic methods and operational taxonomic unit (OTU) delimitations, suggests that the genus Lactarius is diverse in Alaska, with at least 43 putative phylogroups, and 24 and 38 distinct OTUs based on 95% and 97% internal transcribed spacer sequence similarity, respectively. Some OTUs were identified to known species, while others were novel, previously unsequenced groups. Non-asymptotic species accumulation curves, the disparity between observed and estimated richness, and the high number of singleton OTUs indicated that many Lactarius species remain to be found and identified in Alaska. Many Lactarius taxa show strong habitat preference to one of the three major vegetation types in the sampled regions (arctic tundra, black spruce forests, and mixed birch-aspen-white spruce forests), as supported by statistical tests of UniFrac distances and principal coordinates analyses (PCoA). Together, our data robustly demonstrate great diversity and nonrandom ecological partitioning in an important boreal ectomycorrhizal genus within a relatively small geographical region. The observed diversity of Lactarius was much higher in either type of boreal forest than in the arctic tundra, supporting the widely recognized pattern of decreasing species richness with increasing latitude.     

Community composition of root‐associated fungi in a Quercus‐dominated temperate forest: “codominance” of mycorrhizal and root‐endophytic fungi

In terrestrial ecosystems, plant roots are colonized by various clades of mycorrhizal and endophytic fungi. Focused on the root systems of an oak‐dominated temperate forest in Japan, we used 454 pyrosequencing to explore how phylogenetically diverse fungi constitute an ecological community of multiple ecotypes. In total, 345 operational taxonomic units (OTUs) of fungi were found from 159 terminal‐root samples from 12 plant species occurring in the forest. Due to the dominance of an oak species (Quercus serrata), diverse ectomycorrhizal clades such as Russula, Lactarius, Cortinarius, Tomentella, Amanita, Boletus, and Cenococcum were observed. Unexpectedly, the root‐associated fungal community was dominated by root‐endophytic ascomycetes in Helotiales, Chaetothyriales, and Rhytismatales. Overall, 55.3% of root samples were colonized by both the commonly observed ascomycetes and ectomycorrhizal fungi; 75.0% of the root samples of the dominant Q. serrata were so cocolonized. Overall, this study revealed that root‐associated fungal communities of oak‐dominated temperate forests were dominated not only by ectomycorrhizal fungi but also by diverse root endophytes and that potential ecological interactions between the two ecotypes may be important to understand the complex assembly processes of belowground fungal communities.     

Fungi ahoy! Diversity on marine wooden substrata in the high North

Marine fungi are severely understudied in the polar regions. We used molecularly identified cultures to study fungi inhabiting 50 intertidal and sea-floor logs along the North Norwegian coast. The aim was to explore the taxonomic and ecological diversity and to examine factors shaping the marine wood-inhabiting fungal communities. The 577 pure cultures analyzed clustered into 147 operational taxonomic units (OTUs) based on 97 % ITS sequence similarity. Ascomycota dominated, but OTUs belonging to Basidiomycota, Mucoromycotina and Chytridiomycota were also isolated. Nine OTUs could not be assigned to any fungal phylum. Almost half of the OTUs were considered non-marine. The western and eastern part of the Norwegian Barents Sea coast hosted different communities. Geography, substratum and site level variables contributed to shaping these communities. We characterized a previously overlooked fungal community in a poorly studied area, discovered high diversity and report many taxa for the first time from the marine environment.     

Host effects in high ectomycorrhizal diversity tropical rainforests on ultramafic soils in New Caledonia

Tropical rainforests have been thought to have low prevalence and diversity of ectomycorrhizal symbioses. However, to date, tropical regions have been poorly sampled for ectomycorrhizal fungi. Here, we investigated ectomycorrhizal fungal community diversity and the role of host plants in shaping this diversity in three main ultramafic rainforests in New Caledonia, an archipelago renowned for its exceptional plant diversity and recognized as a biodiversity hotspot. Sampling of ectomycorrhizal root tips and fruit bodies in Nothofagus aequilateralis-dominated, Arillastrum gummiferum-dominated and mixed rainforests showed high fungal diversity with, in total, 28 lineages and 311 operational taxonomic units (OTUs), of which 95% might be endemic. We also found that host preference and host density influenced ectomycorrhizal community composition and contributed to the high fungal diversity of New Caledonian rainforests. Finally, the /cortinarius lineage dominated the below- and above-ground communities, which suggests that this lineage plays a central role in ultramafic ecosystems functioning.     

Ectomycorrhizal fungal communities associated with Masson pine (Pinus massoniana Lamb.) in Pb–Zn mine sites of central south China

To advance our understanding of ectomycorrhizal fungal communities in mining areas, the diversity and composition of ectomycorrhizal fungi associated with Masson pine (Pinus massoniana Lamb.) and soil chemistry were investigated in Taolin lead–zinc (Pb–Zn) mine tailings (TLT), two fragmented forest patches in a Huayuan Pb–Zn mineland (HY1 and HY2), and a non-polluted forest in Taolin in central south China. Ectomycorrhizal fungal species were identified by morphotyping and sequence analyses of the internally transcribed spacer regions of ribosomal DNA. The two study sites in the Huayuan mineland (HY1 and HY2) were significantly different in soil Pb, Zn, and cadmium (Cd) concentrations, but no significant difference was observed in ectomycorrhizal colonization, ectomycorrhizal fungal richness, diversity, or rank–abundance. In addition, the similarity of ectomycorrhizal fungal communities between HY1 and HY2 was quite high (S?rensen similarity index?=?0.47). Thus, the concentration of heavy metals may not be determining factors in the structure of these communities. In the tailings, however, significantly lower ectomycorrhizal colonization and ectomycorrhizal fungal richness were observed. The amounts of Pb and Zn in the tailing sand were higher than the non-polluted forest but far lower than in HY1. Thus, these heavy metals did not account for the reduced colonization and ectomycorrhizal fungal richness in TLT. The ectomycorrhizal fungal community in TLT was dominated by four pioneer species (Rhizopogon buenoi, Tomentella ellisii, Inocybe curvipes, and Suillus granulatus), which collectively accounted for 93.2?% of root tip colonization. The immature soil conditions in tailing (low N and P, sand texture, and lack of organic matter) may only allow certain pioneer ectomycorrhizal fungal species to colonize the site. When soil samples from four sites were combined, we found that the occurrences of major ectomycorrhizal fungal taxa were not clearly related to the concentrations of Pb, Zn, and Cd. In conclusion, our results suggest that ectomycorrhizal fungal communities in mining areas are not necessarily affected by heavy metals themselves but could be largely determined by soil maturity.     

Temporal dynamics of ectomycorrhizal fungal communities in Shorea siamensis forest fragments

Investigating the dynamics of ectomycorrhizal fungal (EMF) communities in seasonally dry tropical forests is essential for sustainable management and for understanding the resilience of this forest type in future climate change scenarios. EMF communities in secondary forest fragments with Shorea siamensis as a single host tree species in central Thailand were sampled seasonally for 2.5 y. Ten EMF taxa were identified from ectomycorrhizal morphotypes, with/tomentella-thelephora and/russula-lactarius as the dominant taxa. Seasonal differences in EMF diversity were not detected; the dominant morphotypes were present in both seasons and their abundance varied. Most EMF taxa exhibited wide environmental ranges and only a few taxa were correlated with soil moisture. Seasonal dynamics of ectomycorrhizal colonization was likely influenced by climatic factors and the phenology of host species. Together, these results suggested that climatic variation may have a long-term and subtle influence on the composition of ectomycorrhizal communities.     

Changes in the root-associated fungal communities along a primary succession gradient analysed by 454 pyrosequencing

We investigated changes in the root-associated fungal communities associated with the ectomycorrhizal herb Bistorta vivipara along a primary succession gradient using 454 amplicon sequencing. Our main objective was to assess the degree of variation in fungal richness and community composition as vegetation cover increases along the chronosequence. Sixty root systems of B. vivipara were sampled in vegetation zones delimited by dated moraines in front of a retreating glacier in Norway. We extracted DNA from rinsed root systems, amplified the ITS1 region using fungal-specific primers and analysed the amplicons using 454 sequencing. Between 437 and 5063 sequences were obtained from each root system. Clustering analyses using a 98.5% sequence similarity cut-off yielded a total of 470 operational taxonomic units (OTUs), excluding singletons. Between eight and 41 fungal OTUs were detected within each root system. Already in the first stage of succession, a high fungal diversity was present in the B. vivipara root systems. Total number of OTUs increased significantly along the gradient towards climax vegetation, but the average number of OTUs per root system stayed unchanged. There was a high patchiness in distribution of fungal OTUs across root systems, indicating that stochastic processes to a large extent structure the fungal communities. However, time since deglaciation had impact on the fungal community structure, as a systematic shift in the community composition was observed along the chronosequence. Ectomycorrhizal basidiomycetes were the dominant fungi in the roots of B. vivipara, when it comes to both number of OTUs and number of sequences.     

高通量测序分析大兴安岭典型森林土壤细菌和真菌群落特征

【背景】大兴安岭地区是我国对气候变化响应最敏感的区域,而土壤微生物在维持寒区森林生态系统结构和功能中发挥重要作用。【目的】探究大兴安岭不同森林类型土壤微生物群落结构及与环境因子的关系。【方法】采用Illumina MiSeq高通量测序技术,分析3种典型森林(白桦林、落叶松林和樟子松林)土壤细菌和真菌群落组成和多样性。【结果】3种林型中共获得2 786个细菌操作分类单元(Operational Taxonomic Unit,OTU),隶属于38门531属,其中优势菌门为变形菌门(Proteobacteria, 31.45%-40.32%)、酸杆菌门(Acidobacteria, 14.24%-40.16%)和放线菌门(Actinobacteria,7.13%-22.15%);1803个真菌OTU隶属于8门263属,其中优势菌门为担子菌门(Basidiomycota,40.43%-62.75%)和子囊菌门(Ascomycota,35.81%-53.68%)。主坐标分析表明,3种林型中细菌和真菌群落组间差异远大于组内差异。Mantel检验结果显示:细菌群落结构与pH、总氮(Total Nitrogen,TN)、总磷(Total Phosphorus,TP)和含水量(Soil Water Content,SWC)具有显著相关性(P0.05),其中pH的相关性系数最大;真菌群落结构与SWC、TN和TP具有显著相关性(P0.05),其中TN的相关性系数最大。冗余分析结果发现,TP与变形菌门、担子菌门相对丰度呈显著正相关,TN和SWC与酸杆菌门、子囊菌门呈显著正相关,pH与放线菌门呈显著正相关(P0.05)。【结论】不同林型间土壤微生物群落结构存在显著差异,明晰其分布规律及主要环境驱动因子,是把握寒区森林生态系统过程的关键。     

Comparison of Bacterial and Fungal Communities Between Natural and Planted Pine Forests in Subtropical China

To improve our understanding of the changes in bacterial and fungal diversity in natural pine and planted forests in subtropical region of China, we examined bacterial and fungal communities from a native and a nearby planted pine forest of the Mt. Lushan by constructing clone libraries of 16S and 18S rRNA genes. For bacterial communities, Proteobacteria and Acidobacteria were dominant bacterial taxa in both two types of forest soils. The Shannon–Wiener diversity index, rarefaction curve analysis, and LibShuff analysis suggest that these two forests contained similar diversity of bacterial communities. Low soil acidity (pH ≈ 4) of our study forests might be one of the most important selection factors determining growth of acidophilic Acidobacteria and Proteobacteria. However, the natural forest harbored greater level of fungal diversity than the planted forest according to the Shannon–Wiener diversity index and rarefaction curve analysis. Basidiomycota and Ascomycota were dominant fungal taxa in the soils of natural and planted forests, respectively. Our results suggest that fungal community was more sensitive than the bacterial community in characterizing the differences in plant cover impacts on the microbial flora in the natural and planted forests. The natural and planted forests may function differently due to the differences in soil fungal diversity and relative abundance.     

Influence of host species on ectomycorrhizal communities associated with two co-occurring oaks (Quercus spp.) in a tropical cloud forest

Interactions between host tree species and ectomycorrhizal fungi are important in structuring ectomycorrhizal communities, but there are only a few studies on host influence of congeneric trees. We investigated ectomycorrhizal community assemblages on roots of deciduous Quercus crassifolia and evergreen Quercus laurina in a tropical montane cloud forest, one of the most endangered tropical forest ecosystems. Ectomycorrhizal fungi were identified by sequencing internal transcribed spacer and partial 28S rRNA gene. We sampled 80 soil cores and documented high ectomycorrhizal diversity with a total of 154 taxa. Canonical correspondence analysis indicated that oak host was significant in explaining some of the variation in ectomycorrhizal communities, despite the fact that the two Quercus species belong to the same red oak lineage (section Lobatae ). A Tuber species, found in 23% of the soil cores, was the most frequent taxon. Similar to oak-dominated ectomycorrhizal communities in temperate forests, Thelephoraceae, Russulaceae and Sebacinales were diverse and dominant.     

天山林区土壤真菌多样性及其群落结构

土壤真菌群落结构对森林生态系统功能的维持具有重要作用,目前对天山林区土壤微生物的种类和群落结构了解甚少。为了解天山不同植被类型下土壤真菌的群落动态及优势菌属,使用Illumina MiSeq高通量测序技术,研究天山林区根际土与非根际土中真菌群落组成及多样性。结果表明:(1)对有效序列进行OTU聚类(operational taxonomic unit)后共得到14121个OTUs,经注释划分为7个门、33个纲、109个目、255个科、444个属、677个种;(2)子囊菌门(Ascomycota)和担子囊菌门(Basidiomycota)是天山植物的优势菌门,灌丛中相对丰度较高的有帚枝霉属(Sarocladium)、鬼笔属(Lysurus)、Microidium;云杉林中相对丰度较高的属有镰刀属(Fusarium)、赤霉属(Gibberella)、丝盖伞属(Inocybe);(3)灌丛与云杉林土壤真菌的群落结构和丰富度有显著差异,灌丛土壤真菌的多样性和丰富度更高,云杉林中阴坡的土壤真菌丰富度较高而阳坡和林窗较低;(4)丝盖伞属(Inocybe)、被孢霉属(Mortierella)、赤霉属(Gibberella)、镰刀属(Fusarium)与云杉的生长可能具有密切的关系。本文推测,根际土壤真菌的多样性和丰富度较低可能是导致云杉幼苗成活率低等更新障碍的问题。     

Richness,species composition and functional groups in Agaricomycetes communities along a vegetation and elevational gradient in the Andean Yungas of Argentina

The Neotropics are among the least explored regions from a mycological perspective. A few recent molecular studies in South America have shown high fungal diversity as well as numerous groups of mostly undescribed taxa. Through soil metabarcoding analysis we compared richness and species composition among macrofungal communities, belonging to Agaricales, Russulales, Boletales and Phallomycetidae groups, in three elevational forests types in the subtropical Yungas of Northwestern Argentina (Piedmont forest; Montane forest, Montane cloud forest). The aims of this study were to assess richness of taxonomic and functional groups along the elevation gradient and to assess the relationships between environmental variables and species composition in the studied fungal communities. The results have shown rich Agaricomycetes communities, diversely structured among forests habitats. The elevation gradient differentially affected the richness and distribution of Agaricales, Russulales, Boletales and Phallomycetidae. Based on fungal trophic modes and guilds, the gradient also affected the ectomycorrhizal taxa distribution. When considering the basidiomata growth forms (agaricoid, boletoid, gasteroid, etc.), only the secotioid type showed significant elevational differences. Additional analyses indicated that saprotrophic nutritional mode was dominant along the entire gradient, being partially replaced by biotrophic modes at higher elevations. Fungal communities in the Montane cloud forests are most dissimilar when compared with communities at the Piedmont forest and Montane forest, which is consistent with the different biogeographic origins of these forests. DNA metabarcoding sequence analysis provided detailed information on the diversity and taxonomic and functional composition of macrofungal communities.     

Microbial Diversity in Engineered Haloalkaline Environments Shaped by Shared Geochemical Drivers Observed in Natural Analogues

Microbial communities in engineered terrestrial haloalkaline environments have been poorly characterized relative to their natural counterparts and are geologically recent in formation, offering opportunities to explore microbial diversity and assembly in dynamic, geochemically comparable contexts. In this study, the microbial community structure and geochemical characteristics of three geographically dispersed bauxite residue environments along a remediation gradient were assessed and subsequently compared with other engineered and natural haloalkaline systems. In bauxite residues, bacterial communities were similar at the phylum level (dominated by Proteobacteria and Firmicutes) to those found in soda lakes, oil sands tailings, and nuclear wastes; however, they differed at lower taxonomic levels, with only 23% of operational taxonomic units (OTUs) shared with other haloalkaline environments. Although being less diverse than natural analogues, bauxite residue harbored substantial novel bacterial taxa, with 90% of OTUs nonmatchable to cultured representative sequences. Fungal communities were dominated by Ascomycota and Basidiomycota, consistent with previous studies of hypersaline environments, and also harbored substantial novel (73% of OTUs) taxa. In bauxite residues, community structure was clearly linked to geochemical and physical environmental parameters, with 84% of variation in bacterial and 73% of variation in fungal community structures explained by environmental parameters. The major driver of bacterial community structure (salinity) was consistent across natural and engineered environments; however, drivers differed for fungal community structure between natural (pH) and engineered (total alkalinity) environments. This study demonstrates that both engineered and natural terrestrial haloalkaline environments host substantial repositories of microbial diversity, which are strongly shaped by geochemical drivers.