Inoculation of willows (Salix spp.) with ectomycorrhizal fungi on mined boreal peatland

Inoculation with ectomycorrhizal fungi was explored as a means to improve productivity of experimental short-rotation plantations of the willowsSalix viminalis andSalix dasyclados for biomass production on surface-mined peatlands in northern Finland. Both willow species formed ectomycorrhizas withAmanita spp.,Cortinarius purpurascens, Entoloma nidorosum, otherEntoloma spp.,Hebeloma crustuliniforme, H. pusillum, Laccaria bicolor, andPaxillus involutus in greenhouse experiments.Field trials on a mined peatland site revealed (after one growing season) statistically significant growth stimulation after inoculation due to mycorrhiza formation in both willow species: plants inoculated withEntoloma were sometimes twice as large as control plants. However, such effects were observed only in plots receiving normal phosphate fertilization as opposed to low phosphate application, and were not consistent from season to season. With the inoculum of other species (Cortinarius, Hebeloma andPaxillus) some evidence of growth enhancement was found in the field, but these results were sometimes attributable to non-symbiotic effects of inoculation.     

Respiration activity of ectomycorrhizas from Cenococcum geophilum and Lactarius sp. in relation to soil water potential in five beech forests

Forest trees are involved in root symbioses with hundreds of species of ectomycorrhizal fungi which constitute functional guilds able to improve the water and mineral nutrition of host trees. In temperate ecosystems, water shortage is a main factor limiting tree vitality. To assess how soil water conditions affected the physiological state of beech (Fagus silvatica L.) ectomycorrhizal roots, we monitored glucose respiration of two ectomycorrhizal types (Lactarius sp. and Cenococcum geophilum) during two complete growing seasons. Five stands of contrasting soil conditions were chosen in north-eastern France. The top soil horizons were equipped with micropsychrometers for measuring water potential and temperature. Glucose respiration on individual ectomycorrhizas was measured in vitro by trapping [¹⁴C]-CO₂ from radiolabelled glucose. For soil water potential <-0.2 MPa, the potential respiration activity of C. geophilumectomycorrhizas was significantly less altered than that of Lactariussp. ectomycorrhizas, indicating that C. geophilumis more likely than Lactariussp. to maintain the physiological integrity of beech roots facing drought stress.     

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.     

The efficiency of evapotranspiration of landfill leachate in the soil–plant system with willow Salix amygdalina L.

The application of a specific species of willow—Salix amygdalina L., marked by high transpiration ability—is a cheap and effective method of landfill leachate disposal. A 2-year study examined the effectiveness of leachate evapotranspiration from soil–plant systems with willow species S. amygdalina L. Evapotranspiration from soil–plant systems planted with willow was from 1.28 up to 5.12 times higher than evaporation from soil surface barren of vegetation. This proves the usefulness of soil–plant systems with willow in landfill leachate treatment through vaporization. Evapotranspiration efficiency, as opposed to total amount of water added into the lysimeter, was not strong enough to vaporize all input of the landfill leachate in the lysimeters. This may indicate that the ground water requires isolation when soil systems remain under landfill leachate irrigation. Linear dependence between willow biomass growth and transpiration was observed to be significant (p < 0.05). Additionally, the research showed that the application of sewage sludge into the soil caused an increase in vaporization efficiency.     

Habitat matters: The role of spore bank fungi in early seedling establishment of Florida slash pines

This study investigated broad patterns in communities of ectomycorrhizal fungi from three Florida habitats (sandhills, scrub, and pine rocklands) and the ability of spore bank fungi to associate with Pinus elliottii (slash pine) and Pinus densa (south Florida slash pine). Efforts to replant pines in the endangered pine rocklands are vital to the persistence of this habitat, yet little is known about the ectomycorrhizal fungi communities or how they may differ from those in other pine-dominated habitats in Florida. We used high-throughput amplicon sequencing (HTS) to assess baseline fungal communities and greenhouse bioassays to bait ectomycorrhizal fungi using seedlings. HTS soil data recovered 188 ectomycorrhizal species but only a few subsequently colonized the bioassay seedlings. We recovered 21 ectomycorrhizal species on pine seedlings including common spore bank fungi such as Cenococcum, Suillus, and Tuber, but Rhizopogon species were dominant across all sites and habitats. Habitat type and site were significant variables influencing the community composition of the total soil fungal community, soil ectomycorrhizal community, and the fungi found on seedling root tips. However, we found no significant differences between the ectomycorrhizal communities on seedling roots from the two Pinus species.     

Attributing functions to ectomycorrhizal fungal identities in assemblages for nitrogen acquisition under stress

Mycorrhizal fungi have a key role in nitrogen (N) cycling, particularly in boreal and temperate ecosystems. However, the significance of ectomycorrhizal fungal (EMF) diversity for this important ecosystem function is unknown. Here, EMF taxon-specific N uptake was analyzed via ¹⁵N isotope enrichment in complex root-associated assemblages and non-mycorrhizal root tips in controlled experiments. Specific ¹⁵N enrichment in ectomycorrhizas, which represents the N influx and export, as well as the exchange of ¹⁵N with the N pool of the root tip, was dependent on the fungal identity. Light or water deprivation revealed interspecific response diversity for N uptake. Partial taxon-specific N fluxes for ectomycorrhizas were assessed, and the benefits of EMF assemblages for plant N nutrition were estimated. We demonstrated that ectomycorrhizal assemblages provide advantages for inorganic N uptake compared with non-mycorrhizal roots under environmental constraints but not for unstressed plants. These benefits were realized via stress activation of distinct EMF taxa, which suggests significant functional diversity within EMF assemblages. We developed and validated a model that predicts net N flux into the plant based on taxon-specific ¹⁵N enrichment in ectomycorrhizal root tips. These results open a new avenue to characterize the functional traits of EMF taxa in complex communities.     

Arbuscular mycorrhizas and ectomycorrhizas of <Emphasis Type="Italic">Uapaca bojeri</Emphasis> L. (Euphorbiaceae): sporophore diversity,patterns of root colonization,and effects on seedling growth and soil microbial catabolic diversity

The main objectives of this study were (1) to describe the diversity of mycorrhizal fungal communities associated with Uapaca bojeri, an endemic Euphorbiaceae of Madagascar, and (2) to determine the potential benefits of inoculation with mycorrhizal fungi [ectomycorrhizal and/or arbuscular mycorrhizal (AM) fungi] on the growth of this tree species and on the functional diversity of soil microflora. Ninety-four sporophores were collected from three survey sites. They were identified as belonging to the ectomycorrhizal genera Afroboletus, Amanita, Boletus, Cantharellus, Lactarius, Leccinum, Rubinoboletus, Scleroderma, Tricholoma, and Xerocomus. Russula was the most frequent ectomycorrhizal genus recorded under U. bojeri. AM structures (vesicles and hyphae) were detected from the roots in all surveyed sites. In addition, this study showed that this tree species is highly dependent on both types of mycorrhiza, and controlled ectomycorrhization of this Uapaca species strongly influences soil microbial catabolic diversity. These results showed that the complex symbiotic status of U. bojeri could be managed to optimize its development in degraded areas. The use of selected mycorrhizal fungi such the Scleroderma Sc1 isolate in nursery conditions could be of great interest as (1) this fungal strain is very competitive against native symbiotic microflora, and (2) the fungal inoculation improves the catabolic potentialities of the soil microflora.     

Species richness and seasonal abundance of ectomycorrhizal fungi in plantations of<Emphasis Type="Italic"> Eucalyptus dunnii</Emphasis> and<Emphasis Type="Italic"> Pinus taeda</Emphasis> in southern Brazil

The abundance and diversity of ectomycorrhizal fungi (EMF) was assessed based on the collection of basidiocarps during 12 months comprising the spring of 1995, and the summer, autumn, and winter of 1996, in three stands of young, middle-aged, and rotation age plantations of Pinus taeda and Eucalyptus dunnii, in the state of Santa Catarina, southern Brazil. A total of 3,085 collections yielded 34 presumed EMF taxa in ten genera, including mushroom-like and sequestrate species. Fruiting patterns of EMF differed with host and season, and host specificity was apparent in some. The overall relative importance (RI) and the Shannon diversity index (H) suggested that stands of E. dunnii had a more diverse aboveground EMF community than those of P. taeda. Overall, species of Scleroderma and Laccaria were not only the most abundant but also had the highest biomass values. The results show that a small number of species of abundant biomass and a larger number of species of less-abundant biomass characterize each forest class.     

Ectomycorrhizal fungal communities of native and non-native Pinus and Quercus species in a common garden of 35-year-old trees

Non-native tree species have been widely planted or have become naturalized in most forested landscapes. It is not clear if native trees species collectively differ in ectomycorrhizal fungal (EMF) diversity and communities from that of non-native tree species. Alternatively, EMF species community similarity may be more determined by host plant phylogeny than by whether the plant is native or non-native. We examined these unknowns by comparing two genera, native and non-native Quercus robur and Quercus rubra and native and non-native Pinus sylvestris and Pinus nigra in a 35-year-old common garden in Poland. Using molecular and morphological approaches, we identified EMF species from ectomycorrhizal root tips and sporocarps collected in the monoculture tree plots. A total of 69 EMF species were found, with 38 species collected only as sporocarps, 18 only as ectomycorrhizas, and 13 both as ectomycorrhizas and sporocarps. The EMF species observed were all native and commonly associated with a Holarctic range in distribution. We found that native Q. robur had ca. 120% higher total EMF species richness than the non-native Q. rubra, while native P. sylvestris had ca. 25% lower total EMF species richness than non-native P. nigra. Thus, across genera, there was no evidence that native species have higher EMF species diversity than exotic species. In addition, we found a higher similarity in EMF communities between the two Pinus species than between the two Quercus species. These results support the naturalization of non-native trees by means of mutualistic associations with cosmopolitan and novel fungi.     

Share the wealth: Trees with greater ectomycorrhizal species overlap share more carbon

The mutualistic symbiosis between forest trees and ectomycorrhizal fungi (EMF) is among the most ubiquitous and successful interactions in terrestrial ecosystems. Specific species of EMF are known to colonize specific tree species, benefitting from their carbon source, and in turn, improving their access to soil water and nutrients. EMF also form extensive mycelial networks that can link multiple root‐tips of different trees. Yet the number of tree species connected by such mycelial networks, and the traffic of material across them, are just now under study. Recently we reported substantial belowground carbon transfer between Picea, Pinus, Larix and Fagus trees in a mature forest. Here, we analyze the EMF community of these same individual trees and identify the most likely taxa responsible for the observed carbon transfer. Among the nearly 1,200 EMF root‐tips examined, 50%–70% belong to operational taxonomic units (OTUs) that were associated with three or four tree host species, and 90% of all OTUs were associated with at least two tree species. Sporocarp ¹³C signals indicated that carbon originating from labelled Picea trees was transferred among trees through EMF networks. Interestingly, phylogenetically more closely related tree species exhibited more similar EMF communities and exchanged more carbon. Our results show that belowground carbon transfer is well orchestrated by the evolution of EMFs and tree symbiosis.     

Ectomycorrhizal fungal community structure across a bog-forest ecotone in southeastern Alaska

We examined the ectomycorrhizal (ECM) fungal community across a bog-forest ecotone in southeastern Alaska. The bog and edge were both characterized by poorly drained Histosols and a continuous layer of Sphagnum species, ericaceous shrubs, Carex species, and shore pine [Pinus contorta Dougl. ex Loud. var. contorta]. The forest had better-drained Inceptisols and Spodosols, a tree community comprised of western hemlock [Tsuga heterophylla (Raf.) Sarg.], yellow cedar (Thuja plicata Donn ex D. Don.), Sitka spruce [Picea sitchensis (Bong.) Carr.] and shore pine, and an understorey of ericaceous shrubs and herbs. ECM root tip density (tips cm^–3 soil) was significantly greater in the forest than the edge or bog and ECM colonization was significantly different in all three plant communities. The below ground ECM fungal taxa were analyzed using molecular techniques (PCR-RFLP and DNA sequencing). Three ECM fungal taxa, Suillus tomentosus (Kauffman) Singer, Cenococcum geophilum Fr.:Fr, and a Russula species, differed in relative frequency, yet were among the four most frequent in all three plant communities. Although differences in ECM fungal richness were observed across plant communities, unequal sampling of ECM roots due to root density and colonization differences confounded richness comparisons. Using resampling procedures for creating taxon-accumulation curves as a function of sampled ECM roots revealed similarities in cumulative ECM fungal taxa richness across the ecotone.     

Molecular diversity of soil basidiomycete communities in northern-central New South Wales, Australia

Basidiomycete communities were profiled using terminal RFLP (TRFLP) and amplified ribosomal DNA restriction analysis (ARDRA) approaches at seven field sites under differing land use in northern-central New South Wales (NSW), Australia. TRFLP data indicated greater basidiomycete species richness at sites with natural vegetation. Sixty-seven basidiomycete ARDRA-types were detected. Various putatively ectomycorrhizal fungi were detected at all sites with native vegetation. Most ectomycorrhizal taxa had affinities to the genus Tomentella, while two Pisolithus taxa and putatively ectomycorrhizal Cantharellales taxa were also detected. Although soils under woodland or grassland communities supported a range of putatively saprotrophic taxa, only members of the Ceratobasidiales were detected in soils under agricultural land use. This study is the first investigation of fungal communities in soils of northern-central NSW, Australia.     

Potentially pathogenic and biocontrol Ascomycota associated with green wall structures of basket willow (<Emphasis Type="Italic">Salix viminalis</Emphasis> L.) revealed by phenotypic characters and ITS phylogeny

Ascomycota are among the fungi that cause serious willow diseases in all natural habitats worldwide. This study was conducted to determine if basket willow used in green wall structures (GWS) built of willow stems were infected by potentially important fungal diseases or their antagonists in urban areas of eastern Canada. In total, 13 different phenotypic genera belonging to eight families of ascomycetous fungi were isolated and identified according to their sexual and/or asexual forms. Venturia pathogenic species complex were represented by three different anamorphs: Fusicladium, Fusicladium-Cladosporium, and Pollaccia as anamorph. They were responsible for the highest incidence value on leaves (IF > 15%). Cryptodiaporthe, Drepanopeziza, and Glomerella dominated on bark (IF > 5%). A significantly higher incidence value of fungal communities was found on first year than on second year GWS. The correspondence analysis using χ² distance showed that communities of potentially pathogenic species are closely related to diseased plants, while healthy plants often contain biocontrol species such as Cladobotryum mycoparasite on healthy bark and Alternaria sp. antagonist on healthy leaves. The phylogenetic positions of the different fungal taxa and their relationship have been revealed by use of PCR amplified internal transcriber spacer (ITS) region of rDNA.     

Host effects on ectomycorrhizal fungal communities: insight from eight host species in mixed conifer-broadleaf forests

To advance our understanding of host effects on the community structure of ectomycorrhizal fungi (EMF), EMF communities were compared among different host species, genera and families in two mixed conifer-broadleaf forests in Japan. Using molecular identification methods we examined EMF root tips of eight coexisting species belonging to six genera (three families): Abies and Tsuga (Pinaceae), Betula and Carpinus (Betulaceae) and Fagus and Quercus (Fagaceae). In total, 205 EMF species were detected, and the total richness was estimated to exceed 300 species using major estimators. Of the 55 EMF species occurring three or more times, eight showed significantly biased host preference. A Mantel test showed a significantly negative correlation between EMF community similarity and host taxonomic distance. Detrended correspondence analysis separated EMF communities mainly by host taxonomic and successional status. Thus, EMF communities are similar on hosts with similar taxonomic and successional status. A significant proportion of EMF exhibited host specificity, which may contribute to the extremely diverse EMF community in conifer-broadleaf forests.     

Survival of inoculated Laccaria bicolor in competition with native ectomycorrhizal fungi and effects on the growth of outplanted Douglasfir seedlings

The survival, development and mycorrhizal efficiency of a selected strain of Laccaria bicolor along with naturally occurring ectomycorrhizal fungi in a young plantation of Douglas fir was examined. Symbionts were identified and their respective colonization abilities were determined. Eight species of symbiotic fungi, which may have originated in adjacent coniferous forests, were observed on the root systems. Mycorrhizal diversity differed between inoculated (5 taxa) and control (8 taxa) seedlings. Ectomycorrhizal fungi which occurred naturally in the nursery on control seedlings (Thelephora terrestris and Suillus sp.) did not survive after outplanting. Both inoculated and naturally occurring Laccaria species, as well as Cenococcum geophilum, survived on the old roots and colonized the newly formed roots, limiting the colonization by other naturally occurring fungi. Other fungi, such as Paxillus involutus, Scleroderma citrinum and Hebeloma sp. preferentially colonized the old roots near the seedling's collar. Russulaceae were found mainly in the middle section of the root system. Mycorrhizal colonization by Laccaria species on inoculated seedlings (54%) was significantly greater than on controls (13%) which were consequently dominated by the native fungi. Significant differences (up to 239%) were found in the growth of inoculated seedlings, especially in root and shoot weight, which developed mainly during the second year after outplanting. Seedling growth varied with the species of mycorrhizae and with the degree of root colonization. Competitiveness and effectiveness of the introduced strain on improving growth performances of seedlings are discussed.     

Ectomycorrhizal and arbuscular mycorrhizal colonization of two species of floodplain willows

To understand the relationships between the distribution of Chosenia arbutifolia and Salix sachalinensis and their mycorrhizal colonization, changes in the quality and types of ectomycorrhizas and arbuscular mycorrhizas of the seedlings of two species were studied at five different sites with different soil conditions in the floodplain of the Satsunai River, Hokkaido. High ectomycorrhizal and low arbuscular mycorrhizal colonization were found in roots of both plants. Ectomycorrhizal colonization of S. sachalinensis in wet sandy or muddy soil conditions was at the same level as that in dry gravelly sites. In contrast, ectomycorrhizal colonization of C. arbutifolia seedlings was lower from wet sandy sites than that from dry gravelly sites. In all study sites, the same three morphological types of ectomycorrhizas were dominant.     

Changes in ectomycorrhizal community structure on two containerized oak hosts across an experimental hydrologic gradient

Shifts in ectomycorrhizal (ECM) community structure were examined across an experimental hydrologic gradient on containerized seedlings of two oak species, Quercus montana and Quercus palustris, inoculated from a homogenate of roots from mature oak trees. At the end of one growing season, seedlings were harvested, roots were sorted by morphotype, and proportional colonization of each type was determined. DNA was subsequently extracted from individual root tips for polymerase chain reaction, restriction fragment length polymorphism, and rDNA sequencing of the ITS1/5.8S/ITS2 region to determine identities of fungal morphotypes. Twelve distinct molecular types were identified. Analysis of similarity showed that ECM fungal assemblages shifted significantly in composition across the soil moisture gradient. Taxa within the genus Tuber and the family Thelephoraceae were largely responsible for the changes in fungal assemblages. There were also significant differences in ECM community assemblages between the two oak host species. These results demonstrate that the structure of ECM fungal communities depends on both the abiotic and biotic environments and can shift with changes in soil moisture as well as host plant, even within the same genus.     

Multiple species of ectomycorrhizal fungi are frequently detected on individual oak root tips in a tropical cloud forest

The ecological importance of ectomycorrhizal (EM) fungi in tropical ecosystems is increasingly recognized, but few studies have used molecular methods to examine EM fungal communities in tropical forests. The diversity and composition of the EM community on Quercus crassifolia in a tropical montane cloud forest in southern Mexico were characterized using DNA sequencing of single root tips. Individual root tips commonly harbored multiple fungal species that resulted in mixed polymerase chain reaction (PCR) products. By cloning and performing gel extractions on mixed PCR samples, we identified two or more EM fungi on 26% of the root tips. When non-EM fungi were considered, this figure increased to 31% of root tips. A total of 44 EM taxa and nine non-EM taxa were detected on roots from 21 soil cores (104 root tips). Taxa in the families Russulaceae, Cortinariaceae, Inocybaceae, and Thelephoraceae were frequent. This is the first study to characterize the belowground EM community in a tropical montane cloud forest. Electronic supplementary material  The online version of this article (doi:) contains supplementary material, which is available to authorized users.     

Comparative structural study ofQuercus serrata andQ. acutissima formed byPisolithus tinctorius andHebeloma cylindrosporum

Ectomycorrhizas were synthesized in pots and growth pouches betweenQuercus serrata, Q. acutissima, and two ectomycorrhizal fungi,Pisolithus tinctorius andHebeloma cylindrosporum. Root morphology and the structure of the mantle and Hartig net were compared using light, fluorescence, scanning and transmission electron microscopy.P. tinctorius initially colonized root cap cells, and eventually produced a highly branched lateral root system with a complete mantle, whereasH. cylindrosporum promoted root elongation with few hyphae on the root apex surface indicating that interaction between roots differs with fungal species. Hartig net structure and hyphal inclusions varied between all the combinations tested. There were structural differences between mycorrhizas ofH. cylindrosporum/Q. acutissima grown in soil and growth pouches, which indicate that the growth pouch environment can induce artefacts in roots. Fruit bodies ofH. cylindrosporum developed in pots withQ. acutissima. AlthoughP. tinctorius has been used to inoculate oak seedlings in the nursery, results of this study indicate thatH. cylindrosporum may also be an effective ectomycorrhizal fungus forQ. serrata andQ. acutissima.     

Seed germination and seedling physiology of Larix kaempferi and Pinus densiflora in seedbeds with charcoal and elevated CO2

We investigated the effect of ectomycorrhizal colonization, charcoal and CO₂ levels on the germination of seeds of Larix kaempferi and Pinus densiflora, and also their subsequent physiological activity and growth. The seeds were sown in brown forest soil or brown forest soil mixed with charcoal, at ambient CO₂ (360 μmol mol⁻¹) or elevated CO₂ (720 μmol mol⁻¹), with or without ectomycorrhiza. The proportions of both conifer seeds that germinated in forest soil mixed with charcoal were significantly greater than for seeds sown in forest soil grown at each CO₂ level (P < 0.05; t-test). However, the ectomycorrhizal colonization rate of each species grown in brown forest soil mixed with charcoal was significantly lower than in forest soil at each CO₂ treatment [CO₂] (P < 0.01; t-test). The phosphorus concentrations in needles of each seedling colonized with ectomycorrhiza and grown in forest soil were greater than in nonectomycorrhizal seedlings at each CO₂ level, especially for L. kaempferi seedlings (P < 0.05; t-test), but the concentrations in seedlings grown in brown forest soil mixed with charcoal were not increased at any CO₂ level. Moreover, the maximum net photosynthetic rate of each seedling for light and CO₂ saturation (P _max) increased when the seedlings were grown with ectomycorrhiza at 720 μmol mol⁻¹ [CO₂]. Ectomycorrhizal colonization led to an increase in the stem diameter of each species grown in each soil treatment at each CO₂ level. However, charcoal slowed the initial growth of both species of seedling, constraining ectomycorrhizal development. These results indicate that charcoal strongly assists seed germination and physiological activity.