Type Of Wood Decay Research Articles

Factors associated with seedling establishment on logs of different fungal decay types-A seed-sowing experiment.

Wood decay fungi alter the abiotic and biotic properties of deadwood, which are important as nurse logs for seedling regeneration. However, the relationship between fungal decay type and seedling performance has not been evaluated experimentally. In this study, we examined the germination, growth, and survival of six arbuscular mycorrhizal (AM) and six ectomycorrhizal (ECM) tree species on three substrates (pine logs with brown and white rot and soil) by conducting seed-sowing experiments in a mixed forest dominated by Pinus densiflora and Quercus serrata. Analysis using ribosomal DNA internal transcribed spacer 1 (rDNA ITS1) sequencing revealed that the fungal community was significantly different across three substrates. The richness of operational taxonomic units (OTUs) of AM and ECM fungi was the largest on brown rot logs and soil, respectively. The substrate significantly affected the seedling performance when comparing wood decay types, but these were not consistent across the mycorrhizal status of the seedlings. Nevertheless, seedlings of some AM trees showed better growth and enhanced mycorrhizal colonization on brown rot logs than on white rot logs. The wood decay type influenced fungal communities in the logs and the performance of some seedling species partly by different mycorrhizal colonization rates. However, the effect was seedling species dependent and showed no apparent difference between AM and ECM trees.

Diverse Xylaria in the Ecuadorian Amazon and their mode of wood degradation

BackgroundXylaria is a diverse and ecologically important genus in the Ascomycota. This paper describes the xylariaceous fungi present in an Ecuadorian Amazon Rainforest and investigates the decay potential of selected Xylaria species. Fungi were collected at Yasuní National Park, Ecuador during two collection trips to a single hectare plot divided into a 10-m by 10-m grid, providing 121 collection points. All Xylaria fruiting bodies found within a 1.2-m radius of each grid point were collected. Dried fruiting bodies were used for culturing and the internal transcribed spacer region was sequenced to identify Xylaria samples to species level. Agar microcosms were used to assess the decay potential of three selected species, two unknown species referred to as Xylaria 1 and Xylaria 2 and Xylaria curta, on four different types of wood from trees growing in Ecuador including balsa (Ochroma pyramidale), melina (Gmelina arborea), saman (Samanea saman), and moral (Chlorophora tinctoria). ANOVA and post-hoc comparisons were used to test for differences in biomass lost between wood blocks inoculated with Xylaria and uninoculated control blocks. Scanning electron micrographs of transverse sections of each wood and assay fungus were used to assess the type of degradation present.Results210 Xylaria collections were sequenced, with 106 collections belonging to 60 taxa that were unknown species, all with less than 97% match to NCBI reference sequences. Xylaria with sequence matches of 97% or greater included X. aff. comosa (28 isolates), X. cuneata (9 isolates) X. curta and X. oligotoma (7 isolates), and X. apiculta (6 isolates)., All Xylaria species tested were able to cause type 1 or type 2 soft rot degradation in the four wood types and significant biomass loss was observed compared to the uninoculated controls. Balsa and melina woods had the greatest amount of biomass loss, with as much as 60% and 25% lost, respectively, compared to the controls.ConclusionsXylaria species were found in extraordinary abundance in the Ecuadorian rainforest studied. Our study demonstrated that the Xylaria species tested can cause a soft rot type of wood decay and with the significant amount of biomass loss that occurred within a short incubation time, it indicates these fungi likely play a significant role in nutrient cycling in the Amazonian rainforest.

Wood-decay type and fungal guild dominance across a North American log transplant experiment

We incubated 196 large-diameter aspen ( Populus tremuloides ), birch ( Betula papyrifera ), and pine ( Pinus taeda ) logs on the FACE Wood Decomposition Experiment encompassing eight climatically-distinct forest sites in the United States. We sampled dead wood from these large-diameter logs after 2 to 6 y of decomposition and determined wood rot type as a continuous variable using the lignin loss/density loss ratio (L/D) and assessed wood-rotting fungal guilds using high-throughput amplicon sequencing (HTAS) of the ITS-2 marker. We found L/D values in line with a white rot dominance in all three tree species, with pine having lower L/D values than aspen and birch. Based on HTAS data, white rot fungi were the most abundant and diverse wood-rotting fungal guild, and soft rot fungi were more abundant and diverse than brown rot fungi in logs with low L/D values. For aspen and birch logs, decay type was related to the wood density at sampling. For the pine logs, decay type was associated with the balance between white and brown/soft rot fungi abundance and OTU richness. Our results demonstrate that decay type is governed by biotic and abiotic factors, which vary by tree species. • Wood-decay types and wood-rotting fungal guilds were measured in large-diameter decayed logs. • White-rot processes dominated among a wide-range of temperate forest sites. • Decay type was related to the wood decomposition rate for aspen and birch dead wood. • Decay type was associated with wood-rotting fungal guild balance in pine dead wood.

Chemical Characterization and Visualization of Progressive Brown Rot Decay of Wood by Near Infrared Imaging and Multivariate Analysis.

Brown rot fungi cause a type of wood decay characterized by carbohydrate degradation and lignin modification. The chemical and physical changes caused by brown rot are usually studied using bulk analytical methods, but these methods fail to consider local variations within the wood material. In this study we applied hyperspectral near infrared imaging to Scots pine sapwood samples exposed to the brown rot fungi Coniophora puteana and Rhodonia placenta to obtain position-resolved chemical information on the fungal degradative process. A stacked-sample decay test was used to create a succession of decay stages within the samples. The results showed that the key chemical changes associated with decay were the degradation of amorphous and crystalline carbohydrates and an increase in aromatic and carbonyl functionality in lignin. The position-resolved spectral data revealed that the fungi initiated degradation in earlywood, and that earlywood remained more extensively degraded than latewood even in advanced decay stages. Apart from differences in mass losses, the two fungi produced similar spectral changes in a similar spatial pattern. The results show that near infrared imaging is a useful tool for analyzing brown rot decayed wood and may be used to advance our understanding of fungal degradative processes.

Which Is the Best Substrate to Regenerate? A Comparative Pot Experiment for Tree Seedling Growth on Decayed Wood and in Soil

Dead wood is an important microsite for seedling regeneration in forest ecosystems. Although recent studies have found important associations between fungal wood decay type (white rot and brown rot) and both density and species composition of regenerating seedlings, its abiotic and biotic mechanisms are unknown. In the present study, pot experiments were conducted with the seedlings of two ectomycorrhizal tree species (Abies veitchii and Betula ermanii) and two arbuscular mycorrhizal tree species (Chamaecyparis obtusa and Cryptomeria japonica) to evaluate their growth using three substrates: brown rot wood, white rot wood, and soil. Results showed that the shoot growth of B. ermanii grown in white rot wood was greater than in other substrates, but this effect disappeared in sterilized substrates, suggesting some biotic positive effects occur in white rot wood. The seedling weights of Cr. japonica and Ch. obtusa were found to be greater in soil than in wood, and this may be partly attributable to the high mycorrhizal rate of their roots in soil. Colonization of arbuscular and ectomycorrhizal fungi was restricted to the seedlings in unsterilized soil. These results demonstrate the importance of the biological mechanisms affecting seedlings’ preferences for a variety of regeneration microsites and illustrate the need for future experiments to include larger sets of seedling species.

Ecological impacts of fungal wood decay types: A review of current knowledge and future research directions

AbstractI summarize current knowledge about the ecosystem functions of wood decomposition in forests with a particular focus on the effects of fungal wood decay types (traditionally categorized into white‐, brown‐, and soft‐rot) on the community composition of saproxylic organisms, forest tree regeneration, and carbon sequestration. Deadwoods of different decay types show markedly different physicochemical and biological properties. High carbohydrate availability in white‐rotted wood promotes the activities of nitrogen‐fixing bacteria; thus white‐rotted wood is a good dietary source for many wood‐eating invertebrates. In contrast, brown‐rotted wood is unattractive to saproxylic communities due to the high recalcitrance of accumulated lignin, low nutrient content, and low pH. Nevertheless, some species have adapted to these conditions and form distinctive communities on brown‐rotted wood. Tree seedlings that are associated with brown‐rotted wood are symbiotic with arbuscular and ericoid mycorrhizal fungal species, but not ectomycorrhizal species. Thus, the diversity of fungal communities associated with a variety of wood decay types produces habitat diversity for saproxylic communities and promotes biodiversity in forest ecosystems. Wood decay type also affects carbon sequestration in forests as brown‐rotted wood might be more instrumental in soil organic matter accumulation than white‐rotted wood. An important aspect of wood decay type is that the wood decay activities of fungi can have indirect long‐lasting cascading impacts on forest biodiversity by altering the physicochemical properties of deadwood. Including the effects of wood decay type in ecological models is thus important for predicting the long‐term dynamics of biodiversity, vegetation, and carbon cycling in forest ecosystems.

Climate influences the effect of fungal decay type on regeneration of Picea jezoensis var. hondoensis seedlings on decaying logs

Hondo spruce (Picea jezoensis var. hondoensis (Mayr) Rehder)) is separately distributed among several mountainous regions in central Japan as remnant populations of the last glacial period. To identify factors that affect Hondo spruce seedling regeneration on decaying logs, we investigated the relationships between climatic conditions, log properties, including decay type by fungi, and Hondo spruce seedling density on logs using data from seven subalpine Hondo spruce forests in central Japan. The results showed that the presence of soft rot was associated with higher seedling density, and the effect of brown rot in sapwood and white rot in heartwood on the predicted number of spruce seedlings on logs switched from positive to negative with increasing temperature and precipitation. Because soft rot occurs under humid conditions, the use of forest management techniques that increase the number of logs with soft rot in sapwood (e.g., by keeping the forest floor moist) are recommended for the sustainable regeneration of Hondo spruce. However, the relationships between wood decay type and seedling regeneration can also be affected by climate condition and thus are more complex than previously thought.

Polyporales Brown Rot Species Fomitopsis pinicola: Enzyme Activity Profiles, Oxalic Acid Production, and Fe3+-Reducing Metabolite Secretion.

Basidiomycota fungi in the order Polyporales are specified to decomposition of dead wood and woody debris and thereby are crucial players in the degradation of organic matter and cycling of carbon in the forest ecosystems. Polyporales wood-decaying species comprise both white rot and brown rot fungi, based on their mode of wood decay. While the white rot fungi are able to attack and decompose all the lignocellulose biopolymers, the brown rot species mainly cause the destruction of wood polysaccharides, with minor modification of the lignin units. The biochemical mechanism of brown rot decay of wood is still unclear and has been proposed to include a combination of nonenzymatic oxidation reactions and carbohydrate-active enzymes. Therefore, a linking approach is needed to dissect the fungal brown rot processes. We studied the brown rot Polyporales species Fomitopsis pinicola by following mycelial growth and enzyme activity patterns and generating metabolites together with Fenton-promoting Fe3+-reducing activity for 3 months in submerged cultures supplemented with spruce wood. Enzyme activities to degrade hemicellulose, cellulose, proteins, and chitin were produced by three Finnish isolates of F. pinicola Substantial secretion of oxalic acid and a decrease in pH were notable. Aromatic compounds and metabolites were observed to accumulate in the fungal cultures, with some metabolites having Fe3+-reducing activity. Thus, F. pinicola demonstrates a pattern of strong mycelial growth leading to the active production of carbohydrate- and protein-active enzymes, together with the promotion of Fenton biochemistry. Our findings point to fungal species-level "fine-tuning" and variations in the biochemical reactions leading to the brown rot type of wood decay.IMPORTANCEFomitopsis pinicola is a common fungal species in boreal and temperate forests in the Northern Hemisphere encountered as a wood-colonizing saprotroph and tree pathogen, causing a severe brown rot type of wood degradation. However, its lignocellulose-decomposing mechanisms have remained undiscovered. Our approach was to explore both the enzymatic activities and nonenzymatic Fenton reaction-promoting activities (Fe3+ reduction and metabolite production) by cultivating three isolates of F. pinicola in wood-supplemented cultures. Our findings on the simultaneous production of versatile enzyme activities, including those of endoglucanase, xylanase, β-glucosidase, chitinase, and acid peptidase, together with generation of low pH, accumulation of oxalic acid, and Fe3+-reducing metabolites, increase the variations of fungal brown rot decay mechanisms. Furthermore, these findings will aid us in revealing the wood decay proteomic, transcriptomic, and metabolic activities of this ecologically important forest fungal species.

The effects of wood decay type on the growth of bryophyte gametophytes

Deadwood is an important habitat for bryophytes in boreal and subalpine forests. The type of decay in wood (white, brown, and soft rot) caused by fungal colonizers has been revealed to affect bryophyte communities. However, little is known about the effects of decay type on the growth of bryophytes. We tested the effect of wood decay type on gametophyte growth for two common bryophyte species, Scapania bolanderi Austin and Pleurozium schreberi (Brid.) Mitt., which dominate the logs in subalpine coniferous forest on Mt. Ontake, in central Honshu, Japan. We used pot culture experiments in an open-sky nursery field. After eight months of cultivation, the growth of S. bolanderi was larger on brown rot wood than white rot wood, but the growth of P. schreberi was not. Mixed cultures of the two species also showed greater growth on brown rot wood. However, growth of S. bolanderi was significantly smaller than P. schreberi in mixed culture. These results suggest that brown rot wood enhances growth of S. bolanderi, but growth may be reduced under competition from P. schreberi. The results are in agreement with the field observation that brown rot wood has a positive association with S. bolanderi coverage on deadwood.

Regeneration of Cryptomeria japonica seedlings on pine logs in a forest damaged by pine wilt disease: effects of wood decomposer fungi on seedling survival and growth

ABSTRACTEvaluating the environmental factors that affect seedling regeneration on deadwood is important for predicting the forest recovery process after dieback events. Pine wilt disease (PWD) has killed many adult trees of Pinus densiflora in recent decades and consequently created a huge accumulation of deadwood in lowland forests in Japan. These deadwoods are now providing nice seedbeds for variety of tree species including Cryptomeria japonica, which is the most important timber species in Japan. In the present study, we tested the effects of various factors on Cryptomeria seedlings growing on decayed Pinus logs in Japan. In total, 126 individuals of Cryptomeria seedlings (height <50 cm) colonizing on 22 pine logs were investigated. During a 5-month research period from May to October 2015, the survival rate of the seedlings was 87.3%, and the maximum height growth was 32.0 cm. Analysis using generalized linear mixed models revealed that delignified white-rot wood in the sapwood of the logs negatively affected seedling survival and growth. These results suggest that type of wood decay, reflecting fungal wood decomposer activity, would strongly affect survival and growth of Cryptomeria seedlings, although logs were important microsites for their establishment after pine wilt disease.

Fungal wood decomposer activity induces niche separation between two dominant tree species seedlings regenerating on coarse woody material

Decomposition subsystems have an essential role in forest dynamics but few studies demonstrate the effect of microbial decay traits on seedling regeneration. In the present study, we focused on seedling regeneration on coarse woody material (CWM), which is an important regeneration site for forest tree species, and the effects of wood decay type according to fungal decay preference for wood structural components on seedling colonization. Effects of log properties including wood decay type and other environmental variables on seedling density were evaluated by ordination methods and generalized linear models. In total, 22 woody species were recorded as seedlings on Pinus densiflora logs. By ordination analysis, white rot in heartwood and brown rot in sapwood, as well as canopy openness and log diameter, showed significant association with seedling communities. The factors selected for a generalized linear model for explaining seedling densities of the two dominant seedling species Cryptomeria japonica and P. densiflora included brown rot in sapwood and white rot in heartwood, but the effects were different: a positive effect of brown rot on C. japonica and a negative effect of white rot on P. densiflora. These results suggested that wood decay type could induce niche separation between dominant tree species regenerating on CWM.

Interactive effects of wood decomposer fungal activities and bryophytes on spruce seedling regeneration on coarse woody debris

AbstractDecaying logs are important seedbeds in boreal and subalpine forests. However, biotic and abiotic factors and their interactions related to seedling colonization patterns on logs remain unclear. In the present study, we evaluated the influence of bryophyte communities, wood decay type (white‐, brown‐, and soft‐rot) owing to decomposer fungal activities, and environmental abiotic factors on seedling establishment in an old‐growth subalpine coniferous forest in Japan. Among the tree species recorded on the conifer logs, Picea jezoensis var. hondoensis was the most dominant. Log surfaces were covered with distinctive patches of liverwort Scapania bolanderi and moss Pleurozium schreberi (approximately 33% cover for each). Redundancy analysis showed that brown‐rot in sapwood significantly affects the bryophyte and seedling community on the logs. Generalized linear models suggested that the total bryophyte cover, Scapania cover, and white‐rot in heartwood positively associate with Picea seedling density, whereas Pleurozium cover and basal area of adjacent Picea adults negatively associate with Picea seedling density. Results of structural equation modeling suggested that the brown‐rot of sapwood positively associates with Scapania cover that has a positive effect on Picea seedling density. Furthermore, brown‐rot of sapwood inhibited the Pleurozium cover, thus contributing to the Scapania dominance on the logs. These results suggest that fungal wood decomposer activities affect colonization of Picea seedlings in an indirect way via structuring bryophyte community on the logs.

Seedling regeneration on decayed pine logs after the deforestation events caused by pine wilt disease

Coarse woody debris (CWD) forms an important habitat suitable for tree seedling establishment, and the CWD decay process influences tree seedling community. In Japan, a severe dieback of Pinus densiflora Sieb. &amp; Zucc. caused by pine wilt disease (PWD) damaged huge areas of pine stands but creates huge mass of pine CWD. It is important to know the factors influencing seedling colonization on pine CWD and their variations among geographical gradient in Japan to expect forest regeneration in post-PWD stands. I conducted field surveys on the effects of latitude, climates, light condition, decay type of pine logs, and log diameter on tree seedling colonization at ten geographically distinct sites in Japan. In total, 59 tree taxa were recorded as seedlings on pine logs. Among them, 13 species were recorded from more than five sites as adult trees or seedlings and were used for the analyses. A generalized linear model showed that seedling colonization of Pinus densiflora was negatively associated with brown rot in sapwood, while that of Rhus trichocarpa was positively associated with brown rot in heartwood. Regeneration of Ilex macropoda had no relationships with wood decay type but negatively associated with latitude and MAT, while positively with log diameter. These results suggested that wood decay type is a strong determinant of seedling establishment for certain tree species, even at a wide geographical scale; however, the effect is tree species specific.

Unexpected diversity of basidiomycetous endophytes in sapwood and leaves of Hevea

Research on fungal endophytes has expanded dramatically in recent years, but little is known about the diversity and ecological roles of endophytic basidiomycetes. Here we report the analysis of 310 basidiomycetous endophytes isolated from wild and planted populations of the rubber tree genus, Hevea. Species accumulation curves were nonasymptotic, as in the majority of endophyte surveys, indicating that more sampling is needed to recover the true diversity of the community. One hundred eighteen OTUs were delimited, representing nine orders of Basidiomycota (Agaricales, Atheliales, Auriculariales, Cantharellales, Hymenochaetales, Polyporales, Russulales, Septobasidiales, Tremellales). The diversity of basidiomycetous endophytes found inhabiting wild populations of Hevea was comparable to that present in plantations. However, when samples were segregated by tissue type, sapwood of wild populations was found to contain a higher number of species than sapwood of planted trees. Seventy-five percent of isolates were members of the Polyporales, the majority in the phlebioid clade. Most of the species belong to clades known to cause a white-rot type of wood decay. Two species in the insect-associated genus Septobasidium were isolated. The most frequently isolated genera included Bjerkandera, Ceriporia, Phanerochaete, Phlebia, Rigidoporus, Tinctoporellus, Trametes (Polyporales), Peniophora, Stereum (Russulales) and Coprinellus (Agaricales), all of which have been reported as endophytes from a variety of hosts, across wide geographic locations. Literature records on the geographic distribution and host association of these genera revealed that their distribution and substrate affinity could be extended if the endophytic niche was investigated as part of fungal biodiversity surveys.

Effects of White and Brown Rot Decay on Changes of Wood Ultrastructure

Fungal decay results in gradual decomposition of compounds of wood cell walls. Mass loss of wood is usually applied to characterize the decay. However, mechanisms of brown and white rot decay are significantly different, resulting in different degradation of components of wood cell walls. Either type of wood decay should differentially influence wood ultrastructure. The traditionally applied descriptors of wood ultrastructure, i.e. crystallinity, the average spacing of the crystal planes and crystallite size, characterize the ultrastructure in an insufficient way. Crystallographic texture analysis was applied in the present study to characterize changes in wood ultrastructure as a result of brown and white rot decay. The Orientation Distribution Function (ODF) was separately determined for wood decayed by brown rot and white fungi and for several levels of mass loss. A series of crystallographic descriptors was derived from the obtained ODFs. The descriptors consisted of texture index, crystalline volume fraction, and skeleton lines of the ODF. The identified crystallographic orientations confirmed different mechanisms of wood decay for brown and white rot fungi. The observations were supported by different rates of changes of the texture index and evolution of crystalline volume fraction.

Microbial Attack of CCA-Treated Pinus radiata Timber from a Retaining Wall

Light and electron microscopic observations were made of Pinus radiata wood treated to a high retention of copper-chrome-arsenate (CCA), which had failed after approximately 11 years in service. The predominant wood cell wall degradation patterns seen under the light microscope and scanning electron microscope as channels and shallow depressions and which were probably responsible for failure of the pole were shown by transmission electron microscopy to be caused by erosion bacteria. Although this type of wood decay is known, the predominance of attack of deeper regions of the pole by erosion bacteria was unusual and significant in terms of the ecology of wood degrading bacteria. Soft-rot was seen in outer regions of the wood at the groundline but was very rarely seen in deeper regions

Observations on Fomes pomaceus (Pers.) Big. & Guill. infecting plum trees

Summary 1. The incidence of F. pomaceus on plum trees in the Cambridge-shire district is noted. 2. Attention is drawn to the similarity in the type of wood decay produced by F. pomaceus and F. igniarius , and an outline of the results of previous investigations on these two fungi is given. 3. Spores of F. pomaceus are sometimes capable of germination twenty-four weeks after liberation from the sporophores. 4. Isolations of F. pomaceus have been made from decayed wood, and these cultures are found to be identical with those grown from spores. 5. The cultural characters of the fungus are noted and compared with those of the strain isolated by Baxter. 6. The fungus is very resistant to desiccation; a fresh culture was obtained from one that was three and a half years old. 7. A study of the effect of the fungus on plum wood has been made, using microchemical methods. 8. The copious gum formation which is so characteristic of the early stages of decay is associated with removal of starch from the medullary-ray cells. 9. The characteristic feature of the later “white-rot” stage is not a delignification of the woody elements, as was formerly supposed, but the removal of the thick lining layer from the walls of the wood fibres. 10. This internal layer of the wood fibre wall is rich in cellulose, but devoid of the aldehydes which usually, accompany lignin. 11. The last walls of the wood elements to be attacked by the fungus are those of the medullary-ray cells. 12. Healthy Pershore and Victoria plum trees have been inoculated, using both spore and mycelial inocula. The results of the inoculation experiments indicate that F. pomaceus is only feebly parasitic on plum trees, the variety Pershore being slightly more susceptible than the variety Victoria.