Ectomycorrhizal Species Richness Research Articles

The interactive effects of soil fertility and tree mycorrhizal association explain spatial variation of diversity–biomass relationships in a subtropical forest

Abstract Observed biodiversity–ecosystem function (BEF) relationships are highly variable, particularly in natural forests. However, our understanding of the factors that generate these often contradictory patterns, especially the role of different mycorrhizal associations, is still limited. By relating tree species richness and above‐ground biomass (AGB) in a fully mapped 24‐ha subtropical forest dynamics plot, we evaluated the impacts of soil fertility and tree mycorrhizal type in mediating BEF relationships at multiple spatial scales. Our results demonstrate a highly positive total richness effect on AGB for arbuscular mycorrhizal (AM) trees but a negative effect on AGB for ectomycorrhizal (EcM) trees, and their relationships were highly spatial scale dependent. However, the observed BEF relationships turned into positive at small spatial scales (i.e. 10 and 20 m) after controlling for other confounding factors (i.e. topography, soil fertility and AM proportion). In addition, we found significant interactions between soil fertility and species richness on AGB. Specifically, the positive effect of total species richness on AGB for major mycorrhizal types gradually weakened with increasing soil fertility, while the positive effect of EcM species richness on AM AGB gradually enhanced at small spatial scales, suggesting the observed diversity effects can be largely attributed to resource niche complementarity and the role of EcM fungi. Synthesis. We conclude that the variable BEF relationships among forest communities could be explained by spatial variation in abiotic environments and community mycorrhizal composition because different types of symbionts perform different nutrient uptake strategies and ability in protection from antagonists. Our findings provide novel insights into the understanding of the variation in the shape of BEF relationships in natural forests, which is critical for forest management, conservation and restoration in a changing world.

Impact of nitrogen and phosphorus addition on resident soil and root mycobiomes in beech forests

N and P are essential macronutrients for all organisms. How shifts in the availability of N or P affect fungal communities in temperate forests is not well understood. Here, we conducted a factorial P × N fertilization experiment to disentangle the effects of nutrient availability on soil-residing, root-associated, and ectomycorrhizal fungi in beech (Fagus sylvatica) forests differing in P availability. We tested the hypotheses that in P-poor forests, P fertilization leads to enhanced fungal diversity in soil and roots, resulting in enhanced P nutrition of beech, and that N fertilization aggravates P shortages, shifting the fungal communities toward nitrophilic species. In response to fertilizer treatments (1 × 50 kg ha−1 P and 5 × 30 kg ha−1 N within 2 years), the labile P fractions increased in soil and roots, regardless of plant-available P in soil. Root total P decreased in response to N fertilization and root total P increased in response to P addition at the low P site. Ectomycorrhizal species richness was unaffected by fertilizer treatments, but the relative abundances of ectomycorrhizal fungi increased in response to P or N addition. At the taxon level, fungal assemblages were unaffected by fertilizer treatments, but at the order level, different response patterns for saprotrophic fungi among soil and ectomycorrhizal fungi on roots were found. Boletales increased in response to P, and Russulales decreased under N + P addition. Our results suggest that trait conservatism in related species afforded resistance of the resident mycobiome composition to nutritional imbalances.

Post-fire dynamics of ectomycorrhizal fungal communities in a Scots pine (Pinus sylvestris L.) forest of Poland.

BackgroundGlobal warming and drying have markedly enhanced in most forests the risk of fires across the world, which can affect the taxonomic and functional composition of key tree-associated organisms such as ectomycorrhizal (ECM) fungi. The present study was conducted to characterise the alterations in the extent of root ECM colonisation, the ECM fungal communities, and their exploration types (i.e., indicator of ECM soil foraging strategies) in regenerated pines within a burned site as compared with an unburned site (five years after the fire event) in the Forest District Myszyniec, Poland.MethodsTo assess the ECM fungal communities of burned and control sites, soil soil-root monoliths were collected from the study sites in September 2019. A total of 96 soil subsamples were collected for soil analysis and mycorrhizal assessment (6 trees × 2 sites × 4 study plots × 2 microsites (north and south) = 96 subsamples).ResultsThe percentage of root ECM colonisation was significantly lower in the burned site in comparison with the unburned (control) site. However, the ECM species richness did not differ between the control and burned sites. The identified ECM species in both sites were Imleria badia, Thelephora terrestris, Russula paludosa, R. badia, R. turci, R. vesca, Lactarius plumbeus, Phialocephala fortinii, and Hyaloscypha variabilis. The most frequent species in the burned and control sites were I. badia and T. terrestris, respectively. The relative abundances of contact, medium-distance smooth and long-distance exploration types in the burned site were significantly different from the control site, dominated by the medium-distance exploration type in both sites. The abundance of the long-distance exploration type in the burned site was markedly greater (27%) than that of the control site (14%), suggesting that the fire event had favoured this ECM foraging strategy. The results demonstrated that the fire led to reduced ECM colonisation of Scots pine trees in the burned site whereas the species richness was not affected, which can be attributed to degrees of fire-resistance in the ECM species, survival of ECM propagules in deeper soil layers, and/or continuous entry of spores/propagules of the ECM fungi from the adjacent forests via wind, water run-off or animals.

Retention of Matured Trees to Conserve Fungal Diversity and Edible Sporocarps from Short-Rotation Pinus radiata Plantations in Ethiopia.

This study is conducted in the short-rotation plantations from the Afromontane Region of Ethiopia. Sporocarps were sampled weekly in a set of permanent plots (100 m2) in young, medium-aged, and mature Pinus radiata (Don) plantations. Fungal richness, diversity, and sporocarp yields were estimated. Composite soil samples were also collected from each plot to determine explanatory edaphic variables for taxa composition. We collected 92 fungal taxa, of which 8% were ectomycorrhizal (ECM). Taxa richness, the Shannon diversity index, and ECM species richness were higher in mature stands. Interestingly, 26% of taxa were classified as edible. Sporocarp yield showed increasing trends towards matured stands. OM and C/N ratio significantly affected fungal composition and sporocarp production. The deliberate retention of mature trees in a patch form rather than clear felling of the plantations could be useful to conserve and promote fungal diversity and production, including valuable taxa such as Morchella, Suillus, and Tylopilus in older stands. This approach has important implications for forest floor microhabitats, which are important for macrofungal occurrence and production. Thus, this strategy could improve the economic outputs of these plantations in the Afromontane Region, while the mature trees could serve as a bridge for providing fungal inocula to the new plantations.

Effect of contaminated soil on multitrophic interactions in a terrestrial system

The effect of contaminated soil on multitrophic interactions in a terrestrial system was studied in a mesocosm experiment with European beech, larvae of summer chafer, and entomopathogenic nematodes (EPN). Beech seedlings were grown in non-contaminated forest and garden soil contaminated with potential toxic elements Cd, Pb and Zn, and in the absence/presence of summer chafer larvae. Root morphology and ectomycorrhizal communities were analysed. Volatile organic compounds (VOC) emitted from beech roots were investigated by GC-MS. Humulene, β-caryophyllene, borneol and camphor were selected for chemotaxis assay with EPN Steinernema feltiae, S. carpocapsae and Heterorhabditis bacteriophora. Increased root tip density was observed as a response to soil contamination and root herbivory. Soil contamination decreased ectomycorrhizal species richness. Analyses of VOC yielded 14 different compounds. Results showed that the least mobile nematode species towards the VOC tested was S. feltiae. β-caryophyllene was an attractant for S. carpocapsae and humulene a weak attractant for H. bacteriophora. Beech roots emitted VOC that affected movement of EPN. β-caryophyllene was detected in beech roots regardless of treatment, indicating that VOC that affect movement of EPN are emitted even in the absence of direct root herbivore attack.

Studies on Ectomycorrhiza: An Appraisal

Ectomycorrhizal (ECM) fungi are obligate symbionts of dominant vascular plants, liverworts and hornworts. There are reports of about 20,000 to 25,000 ECM fungi that promote plant growth by facilitating enhanced water and nutrient absorption, and provide tolerance to environmental stresses. These below-ground fungi play a key role in terrestrial ecosystems as they regulate plant diversity, nutrient and carbon cycles, and influence soil structure and ecosystem multifunctionality. Because ECM fungi are obligate root symbionts, host plant can have a strong effect on ECM species richness and community composition. The biogeographic pattern and detailed functioning and regulation of these mycorrhizosphere processes are still poorly understood and require detailed study. More recent researches have placed emphasis on a wider, multifunctional perspective, including the effects of ectomycorrhizal symbiosis on plant and microbial communities, and on ecosystem processes. Over the years the main focus in ECM research has been on the study of diversity and specificity of ECM strains, the role of ECM in regeneration of degraded ecosystem, the growth and establishment of seedlings through nutrient acquisition and the mediation of plant responses to various types of stress. In this review, recent progresses in ectomycorrhizal biology are presented, especially the potential role of ECM symbioses in resistance or tolerance to various biotic and abiotic stresses, and in maintinance of plant diversity for proper ecosystem functioning.

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

Alpine treeline ecotones represent ecosystems that are vulnerable to climate change. We investigated the ectomycorrhizal (ECM) community, which has potential to stabilize alpine ecosystems. ECM communities associated with Larix chinensis were studied in four zones along a natural ecotone from a mixed forest stand over pure forest stands, the timberline, and eventually, the treeline (3050-3450m) in Tabai Mountain, China. Sixty operational taxonomic units (OTUs) of ECM fungi were identified by sequencing the rDNA internal transcribed spacer of ECM tips. The richness of ECM species increased with elevation. The soil C/N ratio was the most important factor explaining ECM species richness. The treeline zone harbored some unique ECM fungi whereas no unique genera were observed in the timberline and pure forest zone. Elevation and topography were equally important factors influencing ECM communities in the alpine region. We suggest that a higher diversity of the ECM fungal community associated with L. chinensis in the treeline zone could result from niche differentiation.

Phylogenetic and functional traits of ectomycorrhizal assemblages in top soil from different biogeographic regions and forest types.

Ectomycorrhizal (EM) fungal taxonomic, phylogenetic, and trait diversity (exploration types) were analyzed in beech and conifer forests along a north-to-south gradient in three biogeographic regions in Germany. The taxonomic community structures of the ectomycorrhizal assemblages in top soil were influenced by stand density and forest type, by biogeographic environmental factors (soil physical properties, temperature, and precipitation), and by nitrogen forms (amino acids, ammonium, and nitrate). While α-diversity did not differ between forest types, β-diversity increased, leading to higher γ-diversity on the landscape level when both forest types were present. The highest taxonomic diversity of EM was found in forests in cool, moist climate on clay and silty soils and the lowest in the forests in warm, dry climate on sandy soils. In the region with higher taxonomic diversity, phylogenetic clustering was found, but not trait clustering. In the warm region, trait clustering occurred despite neutral phylogenetic effects. These results suggest that different forest types and favorable environmental conditions in forests promote high EM species richness in top soil presumably with both high functional diversity and phylogenetic redundancy, while stressful environmental conditions lead to lower species richness and functional redundancy.

Can we predict Sphaeropsis sapinea outbreak by monitoring fungal diversity in austrian pine plantations?

Fungal diversity plays an important role in forest ecosystems stability as well in the health status of mycorrhizal forest trees. At research area in Istria, Croatia, pathogenic fungus Sphaeropsis tip blight (Sphaeropsis sapinea (Fr.) Dyko et Sutton) caused substantial damage in Austrian pine (Pinus nigra J. F. Arnold) plantations during the last decades. This research continues on previous done in Austrian pine plantations on predisposition to S. sapinea infections, where site and stress conditions were determined as key factors, but also, the ectomycorrhizal (ECM) fungi were confirmed as biological indicators of the health status in selected plantations. We analyzed fungal diversity of Austrian pine plantations to determine the dependence of species richness and its diversity index, both for total and ECM species only, in relation to S. sapinea infection rate and crown transparency of selected trees. Fungal samples were collected during 2013 at nine permanent research plots in autumn season. Their total and ECM species richness and diversity index were correlated to Sphaeropsis tip blight infection level and crown transparency. Our results did not confirm the hypothesis that Austrian pine plantations with higher total species richness and its diversity index are more resistant to S. sapinea infection nor to crown transparency. Oppositely, ectomycorrhizal species richness and its diversity index might be used as good biological indicators of S. sapinea presence and crown transparency of studied plantations.

Disrupting ectomycorrhizal symbiosis: Indirect effects of an annual invasive plant on growth and survival of beech (Fagus sylvatica) saplings

Understanding how invasive plants modify symbiotic interactions between ectomycorrhizal (EM) fungi and native host trees is a central goal in invasion biology. We examined the effect of the annual invasive plant Impatiens glandulifera on the EM association and performance of Fagus sylvatica saplings in a controlled field experiment at three sites in a deciduous forest in Switzerland. A total of 1188 one-year-old F. sylvatica saplings were planted either in plots invaded by I. glandulifera, in plots from which the invasive plant had been manually removed or in plots which were not yet colonized by the invasive plant. The 54 (3×18) plots were equally distributed over three sites. Saplings, including their full root systems were harvested after 3, 6 and 15 months. Exudates of the invasive plant were extracted from resin bags buried in the soil during the seedling, flowering and senescent stage of I. glandulifera. EM colonization on F. sylvatica saplings growing in invaded plot was 33% lower after 3 months and 66% lower after 15 months than saplings growing in plots from which I. glandulifera had been removed and in uninvaded plots. Survival and biomass of saplings were reduced by 16% and 30% after 15 months in plots invaded by I. glandulifera. Analysis of the internal transcribed spacer region of fungal rDNA (ITS) showed that the number of EM species was highly correlated with the number of EM morphotypes, indicating that the latter can be considered as a surrogate for EM species richness on roots of F. sylvatica saplings. EM morphotype richness on saplings was 32% lower after 15 months in invaded plots as compared to control plots. Chemical analysis revealed a high amount of naphthoquinones in plots with I. glandulifera suggesting that this putative allelochemical can be responsible for the reduction in both EM colonization and morphotype richness. Our findings demonstrate the negative impact of an annual invasive plant on the ectomycorrhizal symbiosis and performance of native F. sylvatica saplings.

Drivers of macrofungal composition and distribution in Yulong Snow Mountain, southwest China

Although environmental factors strongly affect the distribution of macrofungi, few studies have so far addressed this issue. Therefore, to further our understanding of how macrofungi respond to changes in the environment, we investigated the diversityand community composition of fungi based on the presence of fruiting bodies in different environments along an elevation gradient in a subalpine Pine forest at Yulong Snow Mountain in southwest China. Two-hundred and twenty-eight specimens of macrofungi from twelve plots were identified using macro-morphological characteristics. We found that soil temperature had a significantly positive influence on total macrofungal and ectomycorrhizal species richness and diversity, while elevation gradients had a significantly negative influence. Furthermore, total macrofungal and ectomycorrhizal species community composition were significantly influenced by soil temperature and elevation gradients. No significant relationships were found between environment variables and the diversity and community composition of saprotrophic fungi in subalpine pine forest.

Profiling functions of ectomycorrhizal diversity and root structuring in seedlings of Norway spruce (Picea abies) with fast‐ and slow‐growing phenotypes

We studied the role of taxonomical and functional ectomycorrhizal (ECM) fungal diversity in root formation and nutrient uptake by Norway spruce (Picea abies) seedlings with fast- and slow-growing phenotypes. Seedlings were grown with an increasing ECM fungal diversity gradient from one to four species and sampled before aboveground growth differences between the two phenotypes were apparent. ECM fungal colonization patterns were determined and functional diversity was assayed via measurements of potential enzyme activities of eight exoenzymes probably involved in nutrient mobilization. Phenotypes did not vary in their receptiveness to different ECM fungal species. However, seedlings of slow-growing phenotypes had higher fine-root density and thus more condensed root systems than fast-growing seedlings, but the potential enzyme activities of ectomycorrhizas did not differ qualitatively or quantitatively. ECM species richness increased host nutrient acquisition potential by diversifying the exoenzyme palette. Needle nitrogen content correlated positively with high chitinase activity of ectomycorrhizas. Rather than fast- and slow-growing phenotypes exhibiting differing receptiveness to ECM fungi, our results suggest that distinctions in fine-root structuring and in the belowground growth strategy already apparent at early stages of seedling development may explain later growth differences between fast- and slow-growing families.

Measuring ectomycorrhizal fungal dispersal: macroecological patterns driven by microscopic propagules

Dispersal plays a prominent role in most conceptual models of community assembly. However, direct measurement of dispersal across a whole community is difficult at ecologically relevant spatial scales. For cryptic organisms, such as fungi and bacteria, the scale and importance of dispersal limitation has become a major point of debate. We use an experimental island biogeographic approach to measure the effects of dispersal limitation on the ecological dynamics of an important group of plant symbionts, ectomycorrhizal fungi. We manipulated the isolation of uncolonized host seedlings across a natural landscape and used a range of molecular techniques to measure the dispersal rates of ectomycorrhizal propagules and host colonization. Some species were prolific dispersers, producing annual spore loads on the order of trillions of spores per km(2). However, fungal propagules reaching host seedlings decreased rapidly with increasing distance from potential spore sources, causing a concomitant reduction in ectomycorrhizal species richness, host colonization and host biomass. There were also strong differences in dispersal ability across species, which correlated well with the predictable composition of ectomycorrhizal communities associated with establishing pine forest. The use of molecular tools to measure whole community dispersal provides a direct confirmation for a key mechanism underlying island biogeography theory and has the potential to make microbial systems a model for understanding the role of dispersal in ecological theory.

Is the potential for the formation of common mycorrhizal networks influenced by fire frequency?

We investigated the influence of fire return interval length on the ectomycorrhizal (ECM) community of a Pinus pinaster dominated forest and on the potential for common ECM networks (CMNs) between understorey shrubs and P. pinaster. ECM root tips were sampled from five shrub species belonging to the genera Arbutus, Cistus and Halimium and from maritime pine in four areas of central Portugal characterized by differing fire return interval length. Fungal symbionts were identified using molecular techniques with direct sequencing of the nrDNA ITS region. Twenty nine ECM species and sixteen non-ECM root inhabitants were identified. Six years after wildfire disturbance ECM species richness did not differ significantly between unburnt and burnt areas. Nine ECM fungal species were common to pine and shrubs and both their frequency of occurrence and proportion were significantly higher in the unburnt area when compared with both areas subjected to fire. Our study revealed that while the potential for CMNs between understorey shrub species and pine seemed to be maintained in the long fire return interval area, recurrent fires significantly reduced the frequency of occurrence and the proportion of common symbiont species. High fire frequencies could therefore delay the process of re-colonization by pine seedlings limiting their dispersal in new settings.

Species richness and nitrogen supply regulate the productivity and respiration of ectomycorrhizal fungi in pure culture

Abstract The effects of biodiversity of aboveground organisms have been widely investigated in a range of ecosystems, yet whether similar responses are also seen in belowground microbial communities, such as ectomycorrhizal (EM) fungi, are little understood. We investigated, in vitro , the effects of a gradient of 1–8 species of EM fungi interacting with substratum carbon:nitrogen (C:N) ratio on biomass production and CO 2 efflux. The model experimental systems enabled us to recover and measure biomass of individuals within communities and calculate net selection and complementarity effects. Both biomass and CO 2 efflux increased with species richness particularly under high N concentrations. Moreover, net biodiversity effects were largely positive, driven by both selection and complementarity effects. Our results reveal, in pure culture, the implications of EM species richness on community productivity and C cycling, particularly under high N conditions, and constitute the basis for future experiments under natural conditions.

Plant functional traits along environmental gradients in seasonally dry and fire-prone ecosystem

Questions: How does the abundance and richness of plant assemblages with different functional (regeneration and nutrient acquisition) traits vary with fire regime, moisture availability and substrate fertility? What is the role of different functional traits in maintaining plant diversity under changing environmental conditions in seasonally dry and fire-prone environments? Location: Southwest Western Australia. Methods: Plant species abundance and soil nutrients were determined at 16 forest sites with variable fire histories across an aridity gradient. All plant species were classified based on their functional traits as (1) perennial or annual, (2) ectomycorrhizal, arbuscular mycorrhizal, ericoid mycorrhizal, orchid mycorrhizal, proteoid or other non-mycorrhizal, (3) resprouters or seeder, and (4) nitrogen fixer or non-fixer. We used a multivariate (fourth-corner) technique to simultaneously test the significance and direction of the relationship between each of these traits and fire frequency, fire interval length, aridity, and soil N, P and C fractions. Results: The functional response of the vegetation to fire regime was minor and restricted to annual species, which comprised only ∼4% of taxa. Proteoid and ectomycorrhizal species dominated over species with arbuscular and orchid mycorrhizal roots, N-fixers dominated over non-fixers, and seeders dominated over resprouters when N fertility was low but organic labile P was high. Further, proteoid and ectomycorrhizal species richness increased with aridity, while arbuscular mycorrhizal species richness decreased. Conclusions: While the functional composition of southwest Australian vegetation is largely insensitive to changes in fire regime, nutrient acquisition and, to a lesser extent, regeneration traits provide mechanisms for the vegetation community to adjust to changes in resource availability. Thus, diversity responses to environmental change in seasonally dry and fire-prone ecosystems are likely to be primarily mediated by the composition of nutrient acquisition traits in the vegetation community.

Ectomycorrhizal fungal communities on seedlings and conspecific trees of Pinus mugo grown on the coastal dunes of the Curonian Spit in Lithuania

Ectomycorrhizal (ECM) communities of mature trees and regenerating seedlings of a non-native tree species Pinus mugo grown in a harsh environment of the coastal region of the Curonian Spit National Park in Lithuania were assessed. We established three study sites (S1, S2, and S3) that were separated from each other by 15 km. The ECM species richness was rather low in particular for mature, 100-year-old trees: 12 ectomycorrhizal taxa were identified by molecular analysis from 11 distinguished morphotypes. All 12 taxa were present on seedlings and on mature trees, with between 8–11 and 9–11 taxa present on seedlings and mature trees, respectively. Cenococcum geophilum dominated all ECM communities, but the relative abundance of C. geophilum mycorrhizas was nearly two times higher on seedlings than on mature trees. Mycorrhizal associations formed by Wilcoxina sp., Lactarius rufus, and Russula paludosa were also abundant. Several fungal taxa were only occasionally detected, including Cortinarius sp., Cortinarius obtusus, Cortinarius croceus, and Meliniomyces sp. Shannon’s diversity indices for the ECM assemblages of P. mugo ranged from 0.98 to 1.09 for seedling and from 1.05 to 1.31 for mature trees. According to analysis of similarity, the mycorrhizal communities were similar between the sites (R = 0.085; P = 0.06) and only slightly separated between seedlings and mature trees (R = 0.24; P < 0.0001). An incidental fruiting body survey that was conducted weakly reflected the below-ground assessment of the ECM fungal community and once again showed that ECM and fruiting body studies commonly supply different partial accounts of the true ECM fungal diversity. Our results show that P. mugo has moved into quite distinct habitats and is able to adapt a suite of ECM symbionts that sufficiently support growth and development of this tree and allow for natural seedling regeneration.

Temporal dynamics of ectomycorrhizal community composition on root systems of oak seedlings infected with Burgundy truffle

Truffles, the hypogeous ascocarps of the ectomycorrhizal genus Tuber, are currently cultivated in orchards to partially offset declining wild production in Europe. Truffle cultivation begins with inoculation of seedling root systems in the greenhouse. Once the mycorrhizal relationship is well established, colonized seedlings are transplanted to a suitable field site. In the USA, little is known about the effect of indigenous ectomycorrhizal species on colonization of host trees by the European Burgundy truffle fungus (T. aestivum). Here we identify the ectomycorrhizal community composition on inoculated seedlings grown in the greenhouse in three types of potting media. We subsequently monitored the ectomycorrhizal community composition for two years after seedlings were transplanted into a field site that had been prepared for truffle cultivation by lime applications. We found that the infection rates of contaminant ectomycorrhizal species present in the greenhouse declined to low levels in this field site. We also found that after two years in the field, both T. aestivum colonization levels and indigenous ectomycorrhizal species richness and abundance increased, indicating that indigenous species, in the short term, did not displace T. aestivum.

Belowground ectomycorrhizal communities in three Norway spruce stands with different degrees of decline in the Czech Republic

We investigated the ectomycorrhizal communities on the roots of adult trees and seedlings associated with three Norway spruce stands in the Czech Republic using morphological and molecular tools. The stands had different degrees of forest decline due to air pollution. The aims of the study were to obtain information about the belowground ectomycorrhizal community in a heavily damaged spruce forest and to assess whether missing ectomycorrhizal fungal partners could be one of the reasons for the observed lack of regeneration. The ectomycorrhizal species richness on the roots of adult trees was significantly lower in the heavily damaged site Mumlavska hora than in the other two, but less drastically so than that found in a fruitbody survey. The roots of adult trees and seedlings were fully mycorrhizal at this site although they were less species-rich. The most abundant ectomycorrhizal species on the root system of adult trees in all three forest stands was Tylospora fibrillosa, a member of the athelioid clade. It made up over 60% of root tips in Mumlavska hora and its proportion was at least twice that in the other two sites. This species was also an efficient colonizer of roots from seedlings, in particular, in the most damaged site. The different soil properties in this site may have caused the observed differences in the ectomycorrhizal species richness and composition. For example, cation exchange capacity and soil base saturation were lower and the soil more often saturated. However, the number of living trees and their defoliation status may well directly impact the ectomycorrhizal species composition by presumably affecting the amount of carbon delivered to the symbiotic fungal partners. Athelioids and thelephoroids are an important component of the belowground ectomycorrhizal community in most temperate and boreal forests, but the role they play might even be more crucial in stressed forest ecosystems. Based on our results, we suggest that factors other than missing ectomycorrhizal inoculum constrain natural regeneration in the heavily damaged site Mumlavska hora.

Contrasting ectomycorrhizal fungal communities on the roots of co‐occurring oaks (Quercus spp.) in a California woodland

Plant host species is considered an important factor influencing ectomycorrhizal (EM) communities. To gain insights into the role of host species in structuring EM communities, EM communities on sympatric oak (Quercus) species were compared in the Sierra Nevada foothills of California. Using molecular methods (polymerase chain reaction, cloning, restriction fragment length polymorphism and DNA sequencing), EM fungi on roots of deciduous Quercus douglasii and evergreen Quercus wislizeni trees were identified from 64 soil cores. The total EM species richness was 140, of which 40 taxa were detected on both oak hosts. Greater diversity and frequency of EM fungi with epigeous fruiting habit were found on Q. wislizeni, while taxa in the Ascomycota were more frequent and diverse on Q. douglasii. Using ordination, it was determined that both soil extractable phosphorus and oak host species explained a significant proportion of the variation in EM species distribution. These results indicate that plant host species can be an important factor influencing EM fungal community composition, even within congeneric trees.