Changes in Microfungal Communities in Roots of Quercus robur Stumps and their Possible Effect on Colonization by Armillaria

Sixteen fungal communities were sampled by isolating from 0.5–1 cm diameter roots of living trees and stumps of common oak (Quercus robur). The density of fungi was 1.5–2 times greater in roots from stumps than from living trees. The diversity of fungi was similar in living tree roots and stumps. Some of the fungal species with increased densities in stump roots (e.g. Aspergillus kanagawaensis, Chrysosporium pannorum, Cylindrocarpon destructans, C. didymum, Hormiactis candida, Monodictys lepraria, Mycelium radicis atrovirens, Penicillium daleae, P. janczewskii, and Trichocladium opacum) usually stimulated the growth of rhizomorphs of either Armillaria ostoyae or A. gallica in oak‐wood segments in vitro. Eight of 27 isolates that were studied stimulated the rhizomorph growth in both Armillaria spp. It is presumed that the increase in density of `stimulants' may predispose oak stumps to infection by A. ostoyae and A. gallica.     

Colonization of Fungi and Bacteria in Stumps and Roots of Scots Pine after Thinning and Treatment with Rotstop

The research areas were located in the Pisz Forest District, northeast Poland, in 10‐year‐old Scots pine (Pinus sylvestris L.) plantations, established in 2004 on a clear‐cut area. Reforestation was performed without a biological treatment against root pathogens, despite the presence of Heterobasidion annosum and Armillaria ostoyae in roots and stumps of trees growing previously. The aim of this research was to evaluate how thinning and treatment with the biological control agent Rotstop influences bacterial and fungal communities within roots and stumps. Twelve months after thinning, samples were collected from five stumps in each of two seasons, autumn and spring, from stands on two types of site, one previously forested and one agricultural (20 stumps in total). Wood samples were cultured on agar media, and (i) fungi in the upper part of the stump and (ii) in roots and (iii) bacteria in roots were genetically identified. Sequences were genetically identified by comparing sequences with records held in the GenBank database. We found great differences in the frequency of both fungi and bacteria in roots: they were more frequent (i) in healthy stumps compared to stumps infected with pathogens (H. annosum and A. ostoyae), (ii) in postagricultural soil than in forest soil and (iii) after spring rather than autumn biological treatment. The introduced species Phlebiopsis gigantea was only identified in the parts of the stumps which were above ground level. The bacterium Paenibacillus pini was associated with the presence of H. annosum infecting the stumps from the roots side. In areas seriously threatened by root pathogens, biological treatment can play only a limited role. It can spread to the upper part and impede the production of fruitbodies; however, it has no impact on the development of pathogens in deeper root areas.     

Diversity and ecology of <Emphasis Type="Italic">Armillaria</Emphasis> species in virgin forests in the Ukrainian Carpathians

In this study, we investigated the diversity and ecology of Armillaria species in virgin pure beech and mixed conifer forests (15,000 ha) of the Carpathian Biosphere Reserve in Ukraine. Armillaria rhizomorphs were systematically sampled, both from the soil and from the root collar of trees (epiphytic), on 79 plots (25 × 20 m) of a 1.5 × 1.5 km grid. In both forest massifs, rhizomorphs were present in the majority of the soil samples, with an estimated dry weight of 512 kg/ha in the pure beech forests and 223 kg/ha in the mixed conifer forests. Similarly, in both forest massifs, most of the trees inspected had rhizomorphs at the root collar. Species identification based on DNA analyses showed that all five annulated European Armillaria species occur in these virgin forests, as previously observed in managed forests in central Europe. However, differences in the frequencies of the single species were observed. The predominance of the preferentially saprotrophic A. cepistipes and A. gallica (84 and 15% of the specimens, respectively) and the absence of significant pathogenic activity suggest that in these virgin forests Armillaria species are most likely to behave as saprotrophs. Forest management may increase the frequency of the pathogenic species A. ostoyae, which is rare in virgin forests.     

Fungi inhabiting knotwood of Pinus sylvestris infected by Porodaedalea pini

Abundance and diversity of fungi in naturally formed knots of Pinus sylvestris affected by Porodaedalea pini were investigated. Samples were taken from trees that were (i) affected, with internal heartwood decay and no conks, (ii) affected, with internal heartwood decay and conks and (iii) controls. The Illumina sequencing technology was used for amplification of DNA, sequencing and analysis. In total, 566,279 raw sequences were obtained from six samples. Sequences included 74% of culturable and 8.4% of non‐culturable fungi and 17.6% of organisms with no reference sequences in NCBI. Abundance of organisms in knotwood, measured as number of OTUs, ranged from 36,272 (29,506 for fungi) to 178,535 (177,484 for fungi) and differed significantly between two trees in a stand and between stands. The highest and lowest average number of fungal OTUs occurred in infected trees with no conks and in trees with conks, respectively. Number of taxa ranged from 171 to 415 and often differed significantly between two trees in one stand and between stands. Greatest diversity occurred in control trees. The number of fungal taxa shared by two trees in one stand was 67–152 and that shared by two stands was 51–141. The majority of fungi were Ascomycota. Those most common in pines affected by P. pini were Coniochaeta hoffmannii and C. fodinicola (19.65%–59.92%). Infundichalara microchona, Leotiomycetes spp. and Rhinocladiella atrovirens were also present. Another common species, Lecanora conizaeoides, occurred most often in control trees (0.30%–8.82%). Porodaedalea pini was detected only sporadically. Non‐culturable fungi were most frequent in the control trees. The greater average abundance and smaller average diversity of fungi in knots of trees infected by P. pini suggest that the pathogen successfully competes with some fungal species and does not inhibit the growth of survivors. Some fungi detected may contribute to production of natural biocides.     

Patterns of diversity and adaptation in Glomeromycota from three prairie grasslands

Arbuscular mycorrhizal (AM) fungi are widespread root symbionts that often improve the fitness of their plant hosts. We tested whether local adaptation in mycorrhizal symbioses would shape the community structure of these root symbionts in a way that maximizes their symbiotic functioning. We grew a native prairie grass (Andropogon gerardii) with all possible combinations of soils and AM fungal inocula from three different prairies that varied in soil characteristics and disturbance history (two native prairie remnants and one recently restored). We identified the AM fungi colonizing A. gerardii roots using PCR amplification and cloning of the small subunit rRNA gene. We observed 13 operational taxonomic units (OTUs) belonging to six genera in three families. Taxonomic richness was higher in the restored than the native prairies with one member of the Gigaspora dominating the roots of plants grown with inocula from native prairies. Inoculum source and the soil environment influenced the composition of AM fungi that colonized plant roots. Correspondingly, host plants and AM fungi responded significantly to the soil–inoculum combinations such that home fungi often had the highest fitness and provided the greatest benefit to A. gerardii. Similar patterns were observed within the soil–inoculum combinations originating from two native prairies, where five sequence types of a single Gigaspora OTU were virtually the only root colonizers. Our results indicate that indigenous assemblages of AM fungi were adapted to the local soil environment and that this process occurred both at a community scale and at the scale of fungal sequence types within a dominant OTU.     

The Effect of Felling on the Occurrence of Microfungi Stimulatory to Armillaria Rhizomorph Formation in Thin Roots of Quercus robur

Eight fungal assemblages were isolated from thin branch roots (0.5–1 mm diameter) of living oak trees (Quercus robur) and their stumps 2 years after felling. The roots were serially washed or surface‐sterilized with ethanol and hypochlorite. The thin roots were inhabited by fungi that are stimulants of Armillaria rhizomorphs as found previously in thick roots (0.5–1 cm diameter). However, unlike thick roots, the densities of the fungi in serially washed roots were significantly less in stump roots than in living roots. Among the most common ‘stimulants’, the frequencies of Cylindrocarpon didymum, Mortierella gracilis, Mor. microspora var. macrocystis, Mycelium radicis atrovirens, Nectria grammicospora, Pseudogymnoascus roseus and Sporothrix schenckii were usually significantly greater in stump roots than in living roots, while the frequencies of Chrysosporium merdarium, Cy. destructans, Mor. hygrophila, Penicillium adametzii, Pe. citrinum, Pe. daleae, Pe. janczewskii and Pe. spinulosum were usually significantly less in stump roots. The frequency of Trichoderma viride was less in the stump roots. Serial washing of roots was more effective than chemical surface‐sterilization in the detection of Armillaria rhizomorph ‘stimulants’. The significance of these findings in the ecology and risk assessment of Armillaria in plantations is discussed.     

Evidence of hydraulic lift in a young beech and oak mixed forest using 18O soil water labelling

Hydraulic lift (HL) by tree roots in a young, broad-leaved, mixed temperate European forest was investigated during the 2008 growing season by injecting ¹⁸O-enriched soil water at a depth of 75–90 cm under drought conditions experimentally imposed in a rain-exclusion system. Based on sap flow, leaf water potential, 2-D root distribution measurements, soil isotope profiles, and xylem water isotope composition, water acquisition and use by two tree species, beech (Fagus sylvatica) and oak (Quercus petraea) was compared. We showed that, unlike oak, beech experienced a marked decrease in sap flow and predawn leaf water potential with increasing soil drought. This behaviour was logical considering the shallower root system in beech than in oak. Six days after ¹⁸O-labelling, we observed isotopic enrichment in the shallower soil layers. Since the intermediate soil layers did not display any enrichment, our results clearly pointed to hydraulic lift by tree roots. The superficial enrichment that was observed in the vicinity of oak trunks and the increase in the isotopic signature of xylem sap in the oak trees but not in the beech trees confirmed the predominant role of oak in the hydraulic lift at our site. Even though facilitation for water acquisition among species was not observed here, our results suggest a potential positive contribution of species like oak toward maintaining species diversity in mixed forest ecosystems submitted to severe drought events.     

Outbreak of Phytophthora cinnamomi causing severe decline of avocado trees in southern Turkey

Since the summer 2017, severe decline symptoms have been observed on 10- to 25-year-old avocado trees in almost all commercial orchards planted in the Mediterranean coastal region of Turkey. Young, newly planted trees in infected orchards were also affected by the disease. Affected trees showed wilting, leaf discoloration, defoliation and severe dieback. Some trees were completely desiccated. Although fine roots of symptomatic trees usually were decayed, reddish brown cankers also occurred on taproots and lateral roots of heavily infected trees. The pathogens were isolated from necrotic root and soil samples of symptomatic trees, using selective medium and soil baiting, and were identified based on morphological features and DNA sequences of the internal transcribed spacer (ITS) region. One isolate each of Phytophthora cryptogea and P. palmivora was identified, while all other isolates were P. cinnamomi. In addition, a subcortical fan-shaped mycelium, characteristic of Armillaria spp., was observed in the stem base of a symptomatic tree and identified as Armillaria gallica by DNA sequences of the internal transcribed spacer (ITS) and the translational elongation factor 1-α (EF 1-α) gene regions. Pathogenicity of Phytophthora isolates was tested by stem inoculation on one-year-old avocado seedlings. Two months after inoculation, canker lesions developed on stems of seedlings inoculated by any of the three Phytophthora spp. In contrast, collenchyma callus formed over the wound points on control plants over the same time period. This is the first report of P. cinnamomi, P. cryptogea, P. palmivora and A. gallica causing root rot of avocado trees in Turkey. In addition, P. cryptogea and A. gallica are reported for the first time associated with disease on this host. Due to the severe symptoms and widespread occurrence, P. cinnamomi should be considered a potential threat to avocado cultivation and natural ecosystems of this region of Turkey.     

Soil microbial communities associated with giant sequoia: How does the world's largest tree affect some of the world's smallest organisms?

Giant sequoia (Sequoiadendron giganteum) is an iconic conifer that lives in relict populations on the western slopes of the California Sierra Nevada. In these settings, it is unusual among the dominant trees in that it associates with arbuscular mycorrhizal fungi rather than ectomycorrhizal fungi. However, it is unclear whether differences in microbial associations extend more broadly to nonmycorrhizal components of the soil microbial community. To address this question, we used next‐generation amplicon sequencing to characterize bacterial/archaeal and fungal microbiomes in bulk soil (0–5 cm) beneath giant sequoia and co‐occurring sugar pine (Pinus lambertiana) individuals. We did this across two groves with distinct parent material in Yosemite National Park, USA. We found tree‐associated differences were apparent despite a strong grove effect. Bacterial/archaeal richness was greater beneath giant sequoia than sugar pine, with a core community double the size. The tree species also harbored compositionally distinct fungal communities. This pattern depended on grove but was associated with a consistently elevated relative abundance of Hygrocybe species beneath giant sequoia. Compositional differences between host trees correlated with soil pH and soil moisture. We conclude that the effects of giant sequoia extend beyond mycorrhizal mutualists to include the broader community and that some but not all host tree differences are grove‐dependent.     

Estimating the relative nutrient uptake from different soil depths in Quercus robur, Fagus sylvatica and Picea abies

The distribution of fine roots and external ectomycorrhizal mycelium of three species of trees was determined down to a soil depth of 55 cm to estimate the relative nutrient uptake capacity of the trees from different soil layers. In addition, a root bioassay was performed to estimate the nutrient uptake capacity of Rb⁺ and NH₄⁺ by these fine roots under standardized conditions in the laboratory. The study was performed in monocultures of oak (Quercus robur L.), European beech (Fagus sylvatica L.) and Norway spruce [Picea abies (L.) Karst.] on sandy soil in a tree species trial in Denmark. The distribution of spruce roots was found to be more concentrated to the top layer (0–11 cm) than that of oak and beech roots, and the amount of external ectomycorrhizal mycelia was correlated to the distribution of the roots. The uptake rate of [⁸⁶Rb⁺] by oak roots declined with soil depth, while that of beech or spruce roots was not influenced by soil depth. In modelling the nutrient sustainability of forest soils, the utilization of nutrient resources in deep soil layers has been found to be a key factor. The present study shows that the more shallow-rooted spruce can have a similar capacity to take up nutrients from deeper soil layers than the more deeply rooted oak. The distribution of roots and mycelia may therefore not be a reliable parameter for describing nutrient uptake capacity by tree roots at different soil depths.     

Contracting montane cloud forests: a case study of the Andean alder (Alnus acuminata) and associated fungi in the Yungas

Alnus acuminata is a keystone tree species in the Yungas forests and host to a wide range of fungal symbionts. While species distribution models (SDMs) are routinely used for plants and animals to study the effects of climate change on montane forest communities, employing SDMs in fungi has been hindered by the lack of data on their geographic distribution. The well‐known host specificity and common biogeographic history of A. acuminata and associated ectomycorrhizal (ECM) fungi provide an exceptional opportunity to model the potential habitat for this symbiotic assemblage and to predict possible climate‐driven changes in the future. We (1) modeled the present and future distributions of suitable habitats for A. acuminata; (2) characterized fungal communities in different altitudinal zones of the Yungas using DNA metabarcoding of soil and root samples; and (3) selected fungi that were significant indicators of Alnus. Fungal communities were strongly structured according to altitudinal forest types and the presence of Alnus. Fungal indicators of Alnus, particularly ECM and root endophytic fungi, were also detected in Alnus roots. Current and future (year 2050) habitat models developed for A. acuminata predict a 25–50 percent decrease in suitable area and an upslope shift of the suitable habitat by ca. 184–380 m, depending on the climate change scenario. Although A. acuminata is considered to be an effective disperser, recent studies suggest that Andean grasslands are remarkably resistant to forest invasion, and future range contraction for A. acuminata may be even more pronounced than predicted by our models.     

Disturbance of forest by trampling: Effects on mycorrhizal roots of seedlings and mature trees of Fagus sylvatica

The effects of disturbance by recreational activities (trampling) on changes in soil organic matter (SOM) and on mycorrhizal roots of seedlings and mature trees were studied in four stands of a beech (Fagus sylvatica L.) forest near Basel, Switzerland. At each site, comparable disturbed and undisturbed plots were selected. Disturbance reduced ground cover vegetation and leaf litter. Beech seedlings had lower biomass after disturbance. Ergosterol concentration in seedling roots, an indicator of mycorrhizal fungi, was lower in two of the four disturbed plots compared to undisturbed plots; these two disturbed sites had especially low litter levels. Based on ergosterol measurements, mycorrhizas of mature trees did not appear to be negatively affected by trampling. Total fine roots and SOM were higher in the disturbed than in the undisturbed plots at three sites. At the fourth site, fine roots and SOM in the disturbed areas were lower than in the undisturbed areas most probably due to nutrient input following picnic activities. Principal component analysis revealed a close correlation between SOM and fine roots of mature trees as well as litter and seedling biomass. Trampling due to recreational activities caused considerable damage to the vegetation layer and in particular to the beech seedlings and their mycorrhizal fine roots, whereas, roots of mature trees were apparently resilient to trampling.     

Early seed fall and seedling emergence: precursors to tropical restoration

We explore processes of seed immigration and seedling recruitment before an experimental rainforest restoration matures enough to affect either. Twenty-four 30 × 30-m plots were fenced in 12 ha of pasture in 2006. Seeds were collected in ninety-six 1-m⁻² seed traps; recruits were censused in ~12,000 m² in which establishment was allowed. We tested effects of distance from forest, living trees, and stumps of trees cut during site preparation on seed rain in 2007 and effects of these and soil depth on recruits through June 2008. Seed fall and recruitment were not correlated with distance to forest 90–400 m away, nor to living shade trees outside the 160 × 485-m experimental grid. Recruitment differed for animal- and wind-dispersed species in a topographically complex landscape. Recruitment of wind-dispersed species was random with respect to soil depth or distance to recent stumps. Recruitment of animal-dispersed species was multimodal; partial correlations with number of stumps within 30 m of plots were significant with soil depth held constant (P < 0.025), as were correlations of recruitment with soil depth with number of stumps held constant (P < 0.01). Animal-dispersed recruits were often not conspecifics of adults that had been cut, indicating a legacy of attraction by fruiting trees of animals bearing seeds from distant sources. Ecological implications are that recruitment in pastures released from grazing reflects a mix of widely scattered wind-dispersed pioneers and, where animal-dispersed trees exist, multi-modal and decidedly non-random recruitment of pioneer and later successional animal-dispersed trees from seed banks.     

Microclimatic differentiation of gene pools in the Lobaria pulmonaria symbiosis in a primeval forest landscape

Population genetics of the tree‐colonizing lichen Lobaria pulmonaria were studied in the largest primeval beech forest of Europe, covering 10 000 ha. During an intensive survey of the area, we collected 1522 thallus fragments originating from 483 trees, which were genotyped with eight mycobiont‐ and 14 photobiont‐specific microsatellite markers. The mycobiont and photobiont of L. pulmonaria were found to consist of two distinct gene pools, which are co‐existing within small areas of 3–180 ha in a homogeneous beech forest. The small‐scale distribution pattern of the symbiotic gene pools show habitat partitioning of lineages associated with either floodplains or mountain forests. Using approximate Bayesian computation (ABC), we dated the divergence of the two fungal gene pools of L. pulmonaria as the Early Pleistocene. Both fungal gene pools survived the Pleistocene glacial cycles in the Carpathians, although possibly in climatically different refugia. Fungal diversification prior to these cycles and the selection of photobionts with different altitudinal distributions explain the current sympatric, but ecologically differentiated habitat partitioning of L. pulmonaria. In addition, the habitat preferences of the mycobiont are determined by other factors and are rather independent of those of the photobiont at the landscape level. The distinct gene pools should be considered evolutionarily significant units and deserve specific conservation priorities in the future, for example gene pool A, which is a Pliocene relict.     

A unigene set for European beech (Fagus sylvatica L.) and its use to decipher the molecular mechanisms involved in dormancy regulation

Systematic sequencing is the method of choice for generating genomic resources for molecular marker development and candidate gene identification in nonmodel species. We generated 47 357 Sanger ESTs and 2.2M Roche‐454 reads from five cDNA libraries for European beech (Fagus sylvatica L.). This tree species of high ecological and economic value in Europe is among the most representative trees of deciduous broadleaf forests. The sequences generated were assembled into 21 057 contigs with MIRA software. Functional annotations were obtained for 85% of these contigs, from the proteomes of four plant species, Swissprot accessions and the Gene Ontology database. We were able to identify 28 079 in silico SNPs for future marker development. Moreover, RNAseq and qPCR approaches identified genes and gene networks regulated differentially between two critical phenological stages preceding vegetative bud burst (the quiescent and swelling buds stages). According to climatic model‐based projection, some European beech populations may be endangered, particularly at the southern and eastern edges of the European distribution range, which are strongly affected by current climate change. This first genomic resource for the genus Fagus should facilitate the identification of key genes for beech adaptation and management strategies for preserving beech adaptability.     

The occurrence of flowering and fruiting on individual trees over 3 years and their effects on subsequent crown condition

Summary The level of fruiting in four forest trees species (Picea sitchensis, P. abies, Pinus sylvestris and Fagus sylvatica) was monitored in Great Britain over the period 1989–1991. In addition, assessments of crown transparency were available for many of the trees for 1987 and 1988. The monitoring period encompassed severe summer droughts in 1989 and 1990, with wetter conditions in 1991. Variations in the level of fruiting in spruce and beech (Fagus sylvatica L.) were seen, with a marked peak in 1990. No pattern was apparent in Scots pine (Pinus sylvestris L.). Coning, which was greater in trees with the least transparent crowns, had no discernible effect on the crown transparency of the conifers. Cupule production in beech was greatest in trees with the most transparent crowns, and trees with high numbers of cupules in 1990 tended to have greater crown dieback recorded in 1991.     

Subcellular Nutrient Element Localization and Enrichment in Ecto- and Arbuscular Mycorrhizas of Field-Grown Beech and Ash Trees Indicate Functional Differences

Mycorrhizas are the chief organ for plant mineral nutrient acquisition. In temperate, mixed forests, ash roots (Fraxinus excelsior) are colonized by arbuscular mycorrhizal fungi (AM) and beech roots (Fagus sylvatica) by ectomycorrhizal fungi (EcM). Knowledge on the functions of different mycorrhizal species that coexist in the same environment is scarce. The concentrations of nutrient elements in plant and fungal cells can inform on nutrient accessibility and interspecific differences of mycorrhizal life forms. Here, we hypothesized that mycorrhizal fungal species exhibit interspecific differences in mineral nutrient concentrations and that the differences correlate with the mineral nutrient concentrations of their associated root cells. Abundant mycorrhizal fungal species of mature beech and ash trees in a long-term undisturbed forest ecosystem were the EcM Lactarius subdulcis, Clavulina cristata and Cenococcum geophilum and the AM Glomus sp. Mineral nutrient subcellular localization and quantities of the mycorrhizas were analysed after non-aqueous sample preparation by electron dispersive X-ray transmission electron microscopy. Cenococcum geophilum contained the highest sulphur, Clavulina cristata the highest calcium levels, and Glomus, in which cations and P were generally high, exhibited the highest potassium levels. Lactarius subdulcis-associated root cells contained the highest phosphorus levels. The root cell concentrations of K, Mg and P were unrelated to those of the associated fungal structures, whereas S and Ca showed significant correlations between fungal and plant concentrations of those elements. Our results support profound interspecific differences for mineral nutrient acquisition among mycorrhizas formed by different fungal taxa. The lack of correlation between some plant and fungal nutrient element concentrations may reflect different retention of mineral nutrients in the fungal part of the symbiosis. High mineral concentrations, especially of potassium, in Glomus sp. suggest that the well-known influence of tree species on chemical soil properties may be related to their mycorrhizal associates.     

Spatial soil heterogeneity has a greater effect on symbiotic arbuscular mycorrhizal fungal communities and plant growth than genetic modification with Bacillus thuringiensis toxin genes

Maize, genetically modified with the insect toxin genes of Bacillus thuringiensis (Bt), is widely cultivated, yet its impacts on soil organisms are poorly understood. Arbuscular mycorrhizal fungi (AMF) form symbiotic associations with plant roots and may be uniquely sensitive to genetic changes within a plant host. In this field study, the effects of nine different lines of Bt maize and their corresponding non‐Bt parental isolines were evaluated on AMF colonization and community diversity in plant roots. Plants were harvested 60 days after sowing, and data were collected on plant growth and per cent AMF colonization of roots. AMF community composition in roots was assessed using 454 pyrosequencing of the 28S rRNA genes, and spatial variation in mycorrhizal communities within replicated experimental field plots was examined. Growth responses, per cent AMF colonization of roots and AMF community diversity in roots did not differ between Bt and non‐Bt maize, but root and shoot biomass and per cent colonization by arbuscules varied by maize cultivar. Plot identity had the most significant effect on plant growth, AMF colonization and AMF community composition in roots, indicating spatial heterogeneity in the field. Mycorrhizal fungal communities in maize roots were autocorrelated within approximately 1 m, but at greater distances, AMF community composition of roots differed between plants. Our findings indicate that spatial variation and heterogeneity in the field has a greater effect on the structure of AMF communities than host plant cultivar or modification by Bt toxin genes.     

Fungal community composition shifts along a leaf degradation gradient in a European beech forest

Aims

The fungal communities in living and decomposed leaves of European Beech (Fagus sylvatica) were compared to identify the phyllosphere fungi involved in litter decomposition at a site in Bavaria, Germany.

Methods

New primers were designed to cover a broad range of fungal ribosomal DNA sequence diversity. Following ‘environmental PCR’, clone libraries from each of five samples of living leaves (surface-sterilized and untreated), freshly fallen, initially and highly decomposed leaves, were screened using RFLP fingerprinting.

Results

Statistical analysis (ANOSIM) revealed that the fungal communities colonizing living (a) and initially decomposed leaves (c) significantly differed between each other and from freshly fallen (b) and highly decomposed leaves (d). Fungal assemblages of a and d were statistically indistinguishable from each other and from the endophyllous fungal community in living leaves.

Conclusions

The results showed that endophyllous fungi play a role throughout the whole decomposition process of beech leaf litter. Therefore, clarification of the life cycle of certain endophytic and/or soil fungi may only be achieved by considering both phyllosphere and soil habitats.     

General microflora,arbuscular mycorrhizal colonization and occurrence of endophytes in the rhizosphere of two age groups of <Emphasis Type="Italic">Ginkgo biloba</Emphasis> L.of Indian Central Himalaya

The populations of the general microflora (bacteria, actinomycetes and fungi) in the rhizosphere and their corresponding non-rhizosphere soil samples of Ginkgo biloba L. of two age groups (Group A, <25 years-young trees; Group B, >60 years-old trees) growing under a temperate location of Indian Himalayan Region (IHR) have been determined. Observations were also made for the diversity, distribution and colonization of arbuscular mycorrhizal (AM) fungi and occurrence of endophytes in roots of G. biloba. The population of general microflora was found to be higher in the rhizosphere of Group B trees, more clearly reflected in terms of rhizosphere: soil (R:S) ratios. Contrary to this, per cent colonization and spore densities of AM fungi were higher in the rhizosphere of Group A trees as compared to the rhizosphere of Group B. AM fungal colonization was observed mostly in form of loose coils. All the spores detected, belonged to the genus Glomus with five different types. Presence of endophytes (both bacteria and fungi) was observed in the cortical cells of G. biloba roots, more profound in case of Group B trees. Data suggest that, while the species of Glomus dominated the rhizosphere of G. biloba, an inverse correlation exist between the colonization of general microflora and the colonization of AM fungi including endophytes.