Species richness and substrate specificity of lignicolous fungi in the canopy of a temperate,mixed deciduous forest

In the more than twenty years in which long-term canopy research has been conducted, mycology has been largely disregarded. Our studies using a construction crane to gain access to the canopy of a forest in Leipzig, Germany are the first long term investigations assessing the diversity and ecology of wood-decaying fungi in a canopy. Thirty-seven individuals of nine different tree species with a large amount of dead wood were selected. Sampling focussed on the four most prominent tree species Acer pseudoplatanus, Fraxinus excelsior, Quercus robur and Tilia cordata. In the years 2002 and 2003 dead wood was collected in different canopy strata. Dead branches were removed and stored for two weeks in open boxes with high humidity to allow growth of fructifications in the laboratory. 118 different taxa were identified (108 species, 77 genera). Corticioid fungi (e.g., of Corticiaceae, Stereaceae, Hymenochaetaceae) dominated the fungal composition with 37 species, pyrenomycetes were present with 18 species. Agaric fungi (Agaricales and Cortinariales) were scarce. Species with minute basidiomes dominated the fungal composition of this systematic group. Agarics with larger sporomes were found only once and were restricted to strongly decayed branches in shaded canopy areas. Concerning species richness and fungal composition the four tree species mentioned above differed remarkably. As expected, many fungi that grew on bark or slightly decayed wood showed a distinct host and substratum specifity. It is noteworthy that fungi which are purportedly to be non-specific were found on single tree species only.     

Survey of subterranean termites (Isoptera: Rhinotermitidae) in a managed silvicultural plantation in Portugal, using a line-intersection method (LIS)

Subterranean termites (Reticulitermes grassei) were surveyed over successive seasons in a managed eucalyptus plantation in southeastern Portugal for 26 months. Termite activity in seven diameter categories of lying dead wood was investigated by a modified line intersection method (LIS). Each item sampled was inspected and assessed for termite attack and for general (i.e. fungal) decay status using standard protocols. Line intersection is quantitative to the extent that it can link foraging and decay parameters to woody biovolume. It was found that termites selected items with larger diameter, the observed trend showing an exponential character with greater termite attack as diameter increased. Attack by termites was positively associated with prior decay by fungi. A clear positive relationship was shown between rainfall and total woody biovolume containing live termites, underlining the importance of moisture for termite activity. Subterranean termites appeared to be important wood decomposers in the woodland studied, with an average of 30% of lying dead wood branches showing signs of termite attack.     

Marine fungi from two sandy beaches in Portugal

The occurrence of marine fungi associated with, pieces of wood, driftwood and dead plant stems, in the intertidal zone of two sandy beaches on the Portuguese west coast, was surveyed for 5 mo. Out of 90 samples scanned 70% had sporulating marine fungi. Thirty-five marine fungal taxa were identified (27 Ascomycota, six anamorphic fungi and two unidentified taxa), out of which 11 species were common to both beaches. Most taxa were infrequent (< or =10%), with the exception of Kirschsteiniothelia maritima (10-20%). The average number of fungi per sample was 0.91 for both beaches. Fifteen species are new records for Portugal. Samples were examined immediately after they were taken to the laboratory, as well as after incubation in moist chamber, for up to 10 mo.     

Effects of a great cormorant colony on wood-inhabiting fungal communities in a coastal Scots pine forest

We studied the changes in the wood-inhabiting fungal communities on dead wood of Scots pine (Pinus sylvestris) under varying duration and intensity of cormorant nesting. The activities of the birds created large amounts of dead wood, changed wood chemistry and altered stand characteristics. Analyses based on records of fruiting structures of fungi showed that fungal communities in the cormorant colony differed from communities in unaffected forest. Ornithogenic factors impacted least on generalist species and promoted the occurrence of fungi uncharacteristic of coniferous wood or wood in general. The rate of ornithogenic change was rapid: a shift in fungal assemblages was evident by the third year of expansion of the bird colony into unaffected forest. It featured the disappearance of tremelloid fungi, a decline of corticioid fungi and an increase of hyphomycetoid fungi. The proportion of coniferous wood specialists decreased and that of generalists increased. It is expected that the changes in fungal communities will persist until the forest is fully regenerated.     

Bark beetles have a decisive impact on fungal communities in Norway spruce stem sections

To study the importance of insects in the establishment of fungi, stem sections of Norway spruce were placed in mature managed conifer forests in Southeast Sweden. After one or two flying seasons, fungal communities in wood, bark and bark beetle samples were analysed by molecular methods. Excluding insects from stem sections with cages had a significant effect on the fungal community. Small wounds made in the bark to mimic insect activity did not significantly alter the fungal community, indicating that physical holes as such only played a minor role for the insect interaction with the fungal community development. Several white rot species were significantly more abundant in stem sections with insect access and were also detected from bark beetle samples. This suggests that insects do contribute to the development of early fungal succession on dead wood, but that creating small disturbances in the bark only have a minor contributing effect.     

Successional development of wood-inhabiting fungi associated with dominant tree species in a natural temperate floodplain forest

Fungi play a crucial role in dead wood decay, being the major decomposers of wood and affecting microbiota associated with dead wood. We sampled dead wood from five deciduous tree species over more than forty years of decay in a natural European floodplain forest with high tree species diversity. While the assembly of dead wood fungal communities shows a high level of stochasticity, it also indicates clear successional patterns, with fungal taxa either specific for early or late stages of wood decay. No clear patterns of fungal biomass content over time were observed. Out of 220 major fungal operational taxonomic units, less than 8% were associated with a single tree species, most of them with Quercus robur. Tree species and wood chemistry, particularly pH, were the most important drivers of fungal community composition. This study highlights the importance of dead wood and tree species diversity for preserving the biodiversity of fungi.     

古田山国家级自然保护区木腐真菌物种多样性及分布

木腐真菌是微生物的一个重要类群, 主要以倒木为生长基质, 通过产生各种水解酶将倒木的纤维素、木质素和半纤维素分解为小分子物质, 对促进森林生态系统中的营养物质循环发挥着重要的生态功能。于2016年8月在浙江古田山国家级自然保护区开展的木腐真菌野外调查, 利用形态学和DNA序列分析对采集的标本进行了物种鉴定, 并分析了木腐真菌的物种组成和地理成分。在采集的158份标本中鉴定木腐真菌45属92种, 其中白腐真菌78种, 褐腐真菌14种。古田山的木腐真菌物种区系组成中, 热带-亚热带成分比例最高。在158份木腐真菌标本中, 97份标本采自直径大于10 cm的倒木或树桩上, 分属于76个种, 是木腐真菌生长的主要基质大小类型; 48份标本采自直径为2-10 cm的枝干上, 分属38个种; 13份标本采自直径小于2 cm的枝干上, 分属12种。不同腐烂等级倒木上生长的真菌数量和种类差异明显, 其中一级腐烂倒木上采集到9份标本(7种), 二级腐烂倒木上采集到86份标本(45种), 三级腐烂倒木上49份标本(29种), 四级腐烂倒木上14份标本(14种)。结果表明, 林分中倒木直径大小和腐烂程度是影响木腐真菌生长与分布的重要因子。     

Increased CO<Subscript>2</Subscript> evolution caused by heat treatment in wood-decaying fungi

Wood-decaying fungi are regarded as the main decomposers of woody debris in boreal forests. Given that fungal respiration makes a significant contribution to terrestrial carbon flows, it is important to understand how the wood-decaying fungal metabolism is regulated in relation to different environmental conditions and disturbances. In the present study, we investigated the effect of temperature stress on wood decomposition rate in 18 species of wood-decaying fungi, representing a broad range of species–habitat associations. Heat shock duration and temperature were calibrated to match the conditions of a forest fire. We found a general increase in fungal decay rate after heat shock; the response was more pronounced in species associated with fire-prone forests. The underlying mechanism is unclear, but possibly relates to an up-regulation at the cellular level in response to heat shock. Our results show that the decomposition rate of dead wood can be strongly affected by environmental triggers.     

丰林国家级自然保护区木腐真菌多样性与寄主倒木的关系

木腐真菌是一类以木材为生长基质的大型真菌, 通过分泌各种水解酶全部或部分降解木材中的木质素、纤维素和半纤维素, 促进森林生态系统的物质循环, 具有重要的生态功能。本研究调查了丰林国家级自然保护区固定样地中木腐真菌的多样性和倒木特征, 并进行了木腐真菌的物种多样性和数量与倒木的种类、数量、腐朽程度、直径大小等的相关性分析。结果显示: 在样地内共采集木腐真菌标本295份, 经鉴定为93种, Shannon多样性指数为3.86, Simpson指数为0.96。相关性分析发现木腐真菌的数量和种类与直径为2-5 cm和5-10 cm的倒木、2级腐烂的倒木和红松倒木均显著相关。样地中优势倒木寄主分别为槭属(Acer)、榛属(Corylus)、云杉属(Picea)和松属(Pinus), 这4类倒木上生长的木腐真菌种类组成具有明显的差异, 槭属和榛属倒木上的共有优势种主要是三色拟迷孔菌(Daedaleopsis tricolor)、云芝(Trametes versicolor)和桦附毛孔菌(Trichaptum pargamenum), 而松属和云杉属的共有优势种主要有白囊耙齿菌(Irpex lacteus)、云芝、冷杉附毛孔菌(Trichaptum abietinum)和褐紫附毛孔菌(T. fuscoviolaceum)。倒木产生真菌子实体的概率研究表明, 同一类寄主倒木上发生木腐真菌子实体的概率在调查面积增加到0.36 ha后趋于一个定值, 松属倒木中仅有10.2%产生真菌子实体, 槭属和云杉属分别是12.9%和13.4%, 榛属最高, 达到53.7%。本研究结果对于预测森林生态系统中木腐真菌的发生具有重要理论意义。     

Fungal diversity on submerged wood in a tropical stream and an artificial lake

Two collections of submerged wood were made from the Mushroom Research Centre in northern Thailand. One collection comprising 100 samples was made from an artificial lake, which had been made by damming a stream running through a secondary forest. The other collection comprising 90 samples was made from an adjacent non dammed shallow stream running through a similar forest. A total of 68 fungal taxa were recorded during the study and the Shannon–Weiner index (H′) was applied to evaluate the diversities of freshwater fungi. Sørensen’s index (S′) was calculated to evaluate the similarity of different fungal communities. The variation of freshwater fungi on submerged wood between lentic and lotic habitat is discussed and compared with previous studies. A dramatic decrease in species richness and diversity, with significantly changed species composition were observed in the artificial lake as compared to the non dammed stream.     

Quantifying fungal viability in air and water samples using quantitative PCR after treatment with propidium monoazide (PMA)

A method is described to discriminate between live and dead cells of the infectious fungi Aspergillus fumigatus, Aspergillus flavus, Aspergillus terreus, Mucor racemosus, Rhizopus stolonifer and Paecilomyces variotii. To test the method, conidial suspensions were heat inactivated at 85 degrees C or held at 5 degrees C (controls) for 1 h. Polycarbonate filters (25 mm diameter, 0.8 microm pore size) were placed on "welled" slides (14 mm diameter) and the filters treated with either PBS or PMA. Propidium monoazide (PMA), which enters dead cells but not live cells, was incubated with cell suspensions, exposed to blue wavelength light-emitting diodes (LED) to inactivate remaining PMA and secure intercalation of PMA with DNA of dead cells. Treated cells were extracted and the live and dead cells evaluated with quantitative PCR (QPCR). After heat treatment and DNA modification with PMA, all fungal species tested showed an approximate 100- to 1000-fold difference in cell viability estimated by QPCR analysis which was consistent with estimates of viability based on culturing.     

Forest microsite effects on community composition of ectomycorrhizal fungi on seedlings of Picea abies and Betula pendula

Niche differentiation in soil horizons, host species and natural nutrient gradients contribute to the high diversity of ectomycorrhizal fungi in boreal forests. This study aims at documenting the diversity and community composition of ectomycorrhizal fungi of Norway spruce ( Picea abies ) and silver birch ( Betula pendula ) seedlings in five most abundant microsites in three Estonian old-growth forests. Undisturbed forest floor, windthrow mounds and pits harboured more species than brown- and white-rotted wood. Several species of ectomycorrhizal fungi were differentially represented on either hosts, microsites and sites. Generally, the most frequent species in dead wood were also common in forest floor soil. Ordination analyses suggested that decay type determined the composition of EcM fungal community in dead wood. Root connections with in-growing mature tree roots from below affected the occurrence of certain fungal species on seedling roots systems in dead wood. This study demonstrates that ectomycorrhizal fungi differentially establish in certain forest microsites that is attributable to their dispersal and competitive abilities. Elevated microsites, especially decayed wood, act as seed beds for both ectomycorrhizal forest trees and fungi, thus affecting the succession of boreal forest ecosystems.     

Tropische Pilze

Tropical fungi Mycological fieldwork in the tropics is a fascinating activity, because fungi are heterotrophic living beings and acquire nutrients in manyfold ways, often in association with algae, plants, or animals. Numerous fungi live in mutualistic symbiosis with plants or algae (lichens), as parasites of plants, or live on dead plant material. Other fungi kill insects or other animals and use their bodies as substrate to develop fruiting bodies, while a few fungal species live in mutualistic symbiosis with insects. These and further groups of fungi are presented based on examples from Panama. Sometimes, supposed fungal structures turn out to be cases of mimesis – plants or animals copy fungal patterns in order to take cover.     

Fungal wood decomposer activities influence community structures of myxomycetes and bryophytes on coarse woody debris

Dead wood is an important habitat for forest organisms, and wood decay fungi are the principal agents determining the dead wood properties that influence the communities of organisms inhabiting dead wood. In this study, we investigated the effects of wood decomposer fungi on the communities of myxomycetes and bryophytes inhabiting decayed logs. On 196 pine logs, 72 species of fungi, 34 species and seven varieties of myxomycetes, and 16 species of bryophytes were identified. Although white rot was the dominant decay type in sapwood and heartwood, brown and soft rots were also prevalent, particularly in sapwood. Moreover, white rot and soft rot were positively and brown rot negatively correlated with wood pH. Ordination analyses clearly showed a succession of cryptogam species during log decomposition and showed significant correlations of communities with the pH, water content, and decay type of wood. These analyses indicate that fungal wood decomposer activities strongly influence the cryptogam communities on dead wood.     

No support for occurrence of free-living Cladonia mycobionts in dead wood

Lichenised fungi are traditionally assumed to form obligate symbioses with algae or cyanobacteria and to be confined to the surface of their growing substratum. However, in a recent 454 pyrosequencing study of fungal communities in Picea abies logs, lichen-forming fungi were detected at a depth of more than 6 cm in dead wood, implying the existence of free-living lichen mycobionts. To determine whether this was the case, we investigated whether Cladonia spp., the most frequently encountered mycobionts, occurred in wood without their photobionts. We detected green algae in all samples with records of Cladonia spp. Hence, we found no evidence for free-living Cladonia mycobionts in wood. We suggest that the detected Cladonia DNA in these logs originates from vegetative propagules or thallus fragments dispersed into the logs by animals or water. However, the occurrence of free-living stages of other lichen-forming fungal taxa in dead wood cannot be excluded.     

Cryptogam communities on decaying deciduous wood – does tree species diversity matter?

Bryophyte and fungal communities were investigated on fallen trees representing seven deciduous tree species in a mixed near natural nemoral forest. Bryophytes were represented by 41 taxa, including several very frequent species. Of the 296 fungal species, most were recorded with very low frequency and the share of high frequent species was much lower than among the bryophytes. Species turnover was bigger in the fungal communities, compared to the bryophyte communities, and related to a higher extent to measured differences in environmental conditions. Tree species diversity was found to be an important factor for fungal species composition, while only small differences in bryophyte species composition were found between the different tree species. On the other hand bryophyte species richness showed distinct relations to tree species and microclimatic variables, a tendency which was not evident for fungal diversity. It is concluded that the two organism groups to some extent differ in their conservation demands. Thus, conservation of wood-inhabiting bryophytes requires prioritising of large, coherent forest stands in which a stable humid microclimate and a reasonable supply of dead wood is secured. Successful conservation of fungi requires that substantial amounts of dead wood are left for natural decay in a variety of natural forest environments representing different tree species, so that heterogeneity in dead wood types is secured.     

Wood-inhabiting fungal communities in woody debris of Norway spruce (Picea abies (L.) Karst.), as reflected by sporocarps, mycelial isolations and T-RFLP identification

Wood-inhabiting fungi play a key role in forest ecosystems and constitute an essential part of forest biodiversity. We therefore examined the composition and abundance of wood-inhabiting fungi by three methods: sporocarp counts, mycelial culturing and direct amplification of internal transcribed spacer terminal restriction fragment length polymorphism from wood combined with sequencing of reference rDNA. Seven-year-old slash piles left after a thinning were analyzed in a 50-year-old Norway spruce plantation. Fifty-eight fungal species were detected from the piled branches and treetops. More species were revealed by sporocarp counts and cultured mycelia than by direct amplification from wood. In principle, sporocarp monitoring may reveal all fruiting taxa, but it poorly reflects their relative abundance in the wood. In contrast, terminal restriction fragment length polymorphism will record the most frequent fungal taxa in the wood, but it may overlook uncommon taxa. Culturing mycelia from wood gives a bias towards species favoured by the cultural medium. The results demonstrate the advantage and the limitations of these methods to be considered in analyses of fungal communities in wood.     

Comparison of Fungal Activities on Wood and Leaf Litter in Unaltered and Nutrient-Enriched Headwater Streams

Fungi are the dominant organisms decomposing leaf litter in streams and mediating energy transfer to other trophic levels. However, less is known about their role in decomposing submerged wood. This study provides the first estimates of fungal production on wood and compares the importance of fungi in the decomposition of submerged wood versus that of leaves at the ecosystem scale. We determined fungal biomass (ergosterol) and activity associated with randomly collected small wood (<40 mm diameter) and leaves in two southern Appalachian streams (reference and nutrient enriched) over an annual cycle. Fungal production (from rates of radiolabeled acetate incorporation into ergosterol) and microbial respiration on wood (per gram of detrital C) were about an order of magnitude lower than those on leaves. Microbial activity (per gram of C) was significantly higher in the nutrient-enriched stream. Despite a standing crop of wood two to three times higher than that of leaves in both streams, fungal production on an areal basis was lower on wood than on leaves (4.3 and 15.8 g C m⁻² year⁻¹ in the reference stream; 5.5 and 33.1 g C m⁻² year⁻¹ in the enriched stream). However, since the annual input of wood was five times lower than that of leaves, the proportion of organic matter input directly assimilated by fungi was comparable for these substrates (15.4 [wood] and 11.3% [leaves] in the reference stream; 20.0 [wood] and 20.2% [leaves] in the enriched stream). Despite a significantly lower fungal activity on wood than on leaves (per gram of detrital C), fungi can be equally important in processing both leaves and wood in streams.     

Secondary metabolites and nutrients explain fungal community composition in aspen wood

Fungi are the main decomposers of litter and wood, driving carbon and nutrient cycles. Despite a large number of studies, fungal community composition is remarkably difficult to predict. In the present study, we explore the importance of secondary metabolites and nutrient content in wood and bark as determinants of fungal community composition. We used aspen (Populus tremula) logs of similar size, from one location, and measured concentrations of carbon, nitrogen and secondary metabolites in bark and wood sampled shortly after felling. Fungal DNA was extracted from logs directly after felling and after two seasons of decomposition, and the fungal communities were assessed using DNA-metabarcoding. Concentrations of metabolites varied considerably between individual trees, and we also observed significant differences within single trees. Plant metabolites and nitrogen concentrations significantly affected fungal community composition. For the overall fungal communities and for wood saprotrophic fungi, the explanatory power of wood and bark metabolites was highest in logs decomposed over two seasons. In recently felled trees however, concentration of metabolites had a stronger effect on plant pathogens and endophytes. We conclude that secondary metabolites represent an overlooked, but important niche dimension for fungal communities in both functional sapwood and dead wood.     

Evolution of Reproductive Morphology in Leaf Endophytes

The endophytic lifestyle has played an important role in the evolution of the morphology of reproductive structures (body) in one of the most problematic groups in fungal classification, the Leotiomycetes (Ascomycota). Mapping fungal morphologies to two groups in the Leiotiomycetes, the Rhytismatales and Hemiphacidiaceae reveals significant divergence in body size, shape and complexity. Mapping ecological roles to these taxa reveals that the groups include endophytic fungi living on leaves and saprobic fungi living on duff or dead wood. Finally, mapping of the morphologies to ecological roles reveals that leaf endophytes produce small, highly reduced fruiting bodies covered with fungal tissue or dead host tissue, while saprobic species produce large and intricate fruiting bodies. Intriguingly, resemblance between asexual conidiomata and sexual ascomata in some leotiomycetes implicates some common developmental pathways for sexual and asexual development in these fungi.