Comparative study on the durability of heat-treated White Birch (Betula papyrifera) subjected to the attack of brown and white rot fungi

Abstract

The effect of heat treatment on decay resistance of white birch was evaluated for different incubation periods ranging from 2 to 12 weeks using three species of brown rot and one species of white rot fungus. The results of weight loss tests showed that the white rot fungus, Trametes versicolor, effectively degraded the untreated wood (73.5%). While the degradation of untreated wood by brown rot fungi species, Gloephyllum trabeum (11.6%) and Conifora puteana (6.2%), was considerably less compared to T. versicolor, the third brown rot fungi studied, Poria placenta, caused an appreciable degradation of the same species (52.4%). The results clearly showed that the heat treatment reduced the effect of fungi attack on white birch. Increasing the heat treatment temperature from 195 to 215°C resulted in reduction of weight loss, consequently, reduction in fungal attack. As an example, the weight loss reductions due to T. versicolor, P. placenta, G. trabeum and C. puteana attack was 62.2%, 71.3%, 89.6% and 100%, respectively, compared to the weight loss of untreated wood when it is heat treated at 215°C. Thus, these results confirmed that the heat treatment increased the biological resistance of white birch.     

Structural health assessment of in situ timber: An interface between service life planning and timber engineering

Abstract

The in situ assessment of timber structures has gained considerable attention in recent years due to some unexpected failures of public buildings. The assessment of timber, however, has been used in the evaluation of historic structures for a number of years, and the methods employed have evolved from visual observation (which is still one of the most effective ways of evaluating in situ timber) to more sophisticated methods that use various physical phenomena such as stress-wave or X-ray energy attenuation. In the health assessment of timber, effects of biotic elements such as insects and fungi are of interest, which, of course, is always connected with the presence of water in wood. The structural assessment encompasses questions related to the structural integrity of in situ members and the performance of components and the system. The structural health assessment not only focuses on biotic elements but also attempts to quantify engineering properties of the material such as strength degradation, modulus of elasticity, loss of cross-section, extent of checks, and other quantitative parameters needed for subsequent evaluation of the structural system, frequently expressed as load-bearing capacity. Service life planning of a structure is a complex issue that is related not only to the materials but also the environment and the use of the structure. Assessment of the health and properties of existing timber elements yields a piece of information that is necessary but not sufficient for the service life estimate. In the evaluation of structural timber, a mere use of various assessment techniques is not sufficient and usually an involvement of disciplines such as wood anatomy, wood physics, and statistics is needed. A reliable estimate of the parameters of in situ timber requires careful planning of measurements (experiments) since the material is highly variable and any statement about the properties of an element or even the entire system must reflect the random character of the wood properties. This paper will summarize the state-of-the art methods used in the assessment of in situ timber and analyze the strengths and the weaknesses of selected methods. An attempt will be made to outline future directions in the development of in situ assessment methods.     

Histological changes in the cell wall structure during wood decay by Trametes hirsuta and Trametes versicolor in neem (Azadirachta Indica A. Juss)

ABSTRACT

Structural alterations in the wood cell walls of neem inoculated with by Trametes hirsuta and T. versicolor were studied by microscopic methods. In vitro decayed wood showed extensive weight loss of test blocks (26.7 and 41.38% by T. versicolor and T. hirsuta, respectively) at the end of 3 months. Selective delignification in the initial phase followed by simultaneous removal of lignin was evident in test blocks inoculated with both the species. The separation of middle lamellae and patches of cellulosic polysaccharides stained blue with Astra blue in the delignified region of the fiber wall during early stages indicates selective mode of decay. In contrast, the occurrence of erosion troughs with characteristic U-notch in tangential sections is a characteristic feature of simultaneous rot that was apparent after 3 months of incubation. The decay pattern occurred concomitantly in all the xylem elements irrespective of general resistance pattern shown by vessel and axial parenchyma cells. At an advance stage, both species of Trametes showed formation of erosion channels along the microfibrils angle of cellulose which is considered as characteristics of soft rot decay type. The sharing of white rot and soft rot decay pattern by both the fungi suggest a phylogenetic link between both groups of fungi.     

Community of Aphyllophorales and Root Rot in Stumps of Picea abies on Clear-felled Forest Sites in Lithuania

The community of Aphyllophorales fungi in stumps of Picea abies (L.) Karst. and the occurrence of root rot caused by Heterobasidion annosum were investigated at 38 clear-felled sites in Lithuania. Fruit-bodies were recorded on 36.0% of the 3924 examined stumps. The most common were Bjerkandera adusta, Phlebiopsis gigantea, Fomitopsis pinicola, Gloeophyllum sepiarium, Stereum sanguinolentum, Trametes zonata and H. annosum. All species occurred in stumps both with and without established root rot, but B. adusta, F. pinicola, G. sepiarium, T. zonata and Trichaptum abietinum occurred less often in stumps containing root rot, while H. annosum was encountered more often. Greater numbers of fruit-bodies were found on stumps cut in summer than on those cut in winter. The fruiting became most abundant 3-4 yrs after the trees were felled. The abundance of nearly all Aphyllophorales correlated positively with the stump diameter, and on larger stumps, fruit-bodies of several different fungi were more common. The number of stumps containing H. annosum root rot in different sites varied from 9.8% to 68.8%, and was 27.6% on average. The incidence of root rot correlated neither with the age nor with the density of the felled stand, but it correlated negatively with the proportion of deciduous trees within a stand.     

Antifungal effect of bark extracts from some European tree species

The inhibitory effect of methanol bark extracts from six deciduous and three coniferous European tree species were bioassayed against eight fungi from the different damage categories, brown rot, white rot, canker and blue-stain. This is the first report providing data on the antifungal activity of several Europaen tree species against fungi within these damage categories. Generally the decay fungi were more inhibited by the bark extracts than the blue-stain fungi, while the lowest inhibition was found among the cancer fungi. The main pattern found between the fungal groups in relation to the bark extracts in this study is believed to be caused by the route of ingress. Acer platanoides bark extract proved to be the most efficient bark extract tested, significantly reducing the growth rate of all tested fungi. Betula pubescens bark extract generally gave the weakest reduction in growth rate. In this study, the conifer bark extracts were in general more active against the canker and blue stain ascomycete fungi than the deciduous trees extracts.     

Management of fungal root‐rot pathogens in tropical Acacia mangium plantations

Acacia mangium is a fast‐growing tree species. It is mainly planted in large monocultures for pulpwood in South‐East Asia. Root rot has become the most economically damaging disease of this species with high tree mortality rates observed during second and third rotations. Two main types of root rots have been found in A. mangium, viz. brown root‐rot and red‐root disease caused by Phellinus spp. and Ganoderma spp., respectively. To assess the future management options for root rot of A. mangium, we review past and current disease‐management strategies for root rot in different temperate and tropical industrial tree crops. The efficacies of a wide range of silvicultural, chemical and biological options are detailed, and their potential utilization in managing root rot of A. mangium is discussed. We conclude that the current gaps in knowledge regarding identification, biology and disease epidemiology of the root‐rot pathogens will need to be addressed so that effective management options can be developed.     

Records of Bursaphelenchus spp. (Nematoda,Parasitaphelenchidae) in coniferous timber imported from the Asian part of Russia

Coniferous wood imported from the Asian part of Russia was surveyed in Germany (Mukran ferry terminal, highway and railway border station in Frankfurt/Oder) and Austria (railway in Marchegg, Retz and Wr. Neustadt, Lower Austria). The consignments consisted of mixed timber of Pinus/Picea or Pinus/Larix. Out of 625 samples investigated, 51 samples (8.5%) yielded eight Bursaphelenchus species. Bursaphelenchus mucronatus was found 42 times in Pinus, Picea and Larix wood, Bursaphelenchus hylobianum and Bursaphelenchus fraudulentus were detected twice, in Pinus/Larix and in Larix, respectively. The following species were each found once: Bursaphelenchus leoni in mixed timber of Pinus/Picea, Bursaphelenchus ‘borealis’ in Pinus, Bursaphelenchus hellenicus and Bursaphelenchus paracorneolus in Larix. One sample of Larix wood from Krasnoyarsk region contained a few specimens corresponding to Bursaphelenchus xylophilus. Bursaphelenchus mucronatus was present in about 30% of the samples showing signs of insect attack. A Monochamus species was found in a sample from Irkutsk. Most of the B. mucronatus isolates found belonged to the European genotype, whereas the East Asian genotype was found in three instances. This is the first report of B. fraudulentus, B. hellenicus, B. leoni, B. paracorneolus and the East Asian genotype of B. mucronatus in Russia. Bursaphelenchus hylobianum is the only species found in Russian wood and not in Europe so far. The species were identified morphologically and by internal transcribed spacer (ITS)‐restriction fragment length polymorphism (RFLP) technique. Species‐specific ITS‐RFLP patterns were established for B. hylobianum. In the case of the isolate morphologically corresponding to B. xylophilus, DNA extraction from the available low number of specimens failed to yield sufficient rDNA for ITS‐RFLP analysis.     

Diseases on Eucalyptus species in Zimbabwean plantations and woodlots

Zimbabwe embarked on planting Eucalyptus species in the early 1900s. Based on a robust breeding programme, it has become a major source of seed for other countries in and outside Africa. Tree health surveys conducted on Eucalyptus in some east and southern African countries over the past two decades have revealed several important fungal diseases that were previously not known in the region, but little is known regarding these problems in Zimbabwe. The aim of this study was to identify important Eucalyptus diseases across Zimbabwe's agroclimatic regions. Morphological characteristics and DNA sequence data were used to identify pathogens collected to species level. Widespread stem canker diseases, caused by species belonging to the Botryosphaeriaceae and Teratosphaeriaceae, and leaf spot diseases caused by fungi in the Capnodiales, were identified. Armillaria root and stem rot was restricted to a single site in the Eastern Highlands. Fungi that could cause canker or blue stain of timber were isolated from recently harvested stumps and included species of Ceratocystis and Ophiostoma. This study is the first to identify Eucalyptus pathogens to species level in Zimbabwe and we report for the first time the presence of the stem canker pathogen T. gauchensis in southern Africa. The results will provide a foundation for the formulation of future disease management strategies in the country.     

Study on the parasitoids ofPissodes nitidus Roel

A systematic observation and intensive study on the parasitoids ofPissodes nitidus were made in Langxiang and Xin'qing Forestry Bureau in Xiaoing'an Mountain area in 1996–1999, including the diagnosis, life history, biological characteristics ofEurytoma sp. and parasitoid complex ofPissodes nitidus. There were about 70 species of parasitoids onPissodes nitidus, including Eurytomidae, Ichneumonidae and Braconidae etc. Among them,Eurytoma sp. is a dominant species and a braconid,Ipobracon sp. is a subdominant species, and they play an important role in controlling the pest. Biography: HU Chun-xiang (1955-), male, Associate professor in Forest Resources and Environment Collage of Northeast Forestry University, Harbin 150040, P. R. China Responsible editor: Chai Ruihai     

Identification,diversity and host specificity of the wood-decay fungi in major sawmill depots of north-eastern Bangladesh

The study was carried out to identify wood-decay fungi, and quantify the diversity and host preferences of the fungi in major sawmill depots in north-eastern Bangladesh. A total of 23 fungal species belonging to 15 genera in seven families were recorded and identified. The Polyporaceae was the most dominant family, while Schizophyllum commune was the most abundant species among all species recorded. Other commonly observed fungal species were Daldinia concentrica, Trametes versicolor, Trametes coccinea and Flavodon flavus. The Simpson diversity index (0.93) and Shannon–Wiener index (2.90) showed a wide distribution of the wood-decay fungi in the study areas. The species diversity index (0.036), species evenness index (0.92) and species richness index (3.40) indicated a diverse distribution of the fungal species. Two-thirds of the identified fungal species showed significant preferences for their hosts. The host vulnerability was found to be significantly affected by storage facility, duration of storage, depot yard condition, treated or non-treated wood and shade facility. The findings of this work may help sawmill owners to utilize a scientific approach to management of logs and timber stored in depots, to minimize fungal decay before incurring any economic loss.     

Resistance of bamboo scrimber against white-rot and brown-rot fungi

ABSTRACT

Bamboo scrimber is one of the most emerging structural materials for future building applications and it possesses properties comparable to other natural wood-based engineered materials such as glulam, laminated veneer lumber and cross-laminated timber. The goal of this work was to study the decay resistance of bamboo scrimber against white-rot (Trametes versicolor) and brown-rot fungi (Serpula lacrymans). Bamboo scrimber samples were incubated in petri dishes with the wood-decaying fungi and the weight loss after 12 weeks was measured. The surface morphology of fungal-degraded bamboo scrimber was evaluated using optical microscopy. Based on the percentage weight loss, bamboo scrimber could be classified as highly resistant against bio-deterioration by white and brown-rot fungi.     

Fungal–copper interactions in wood examined with large field of view synchrotron-based X-ray fluorescence microscopy

ABSTRACT

The goal of this study was to demonstrate how synchrotron-based X-ray fluorescence microscopy (XFM) can be used to better understand the mechanisms of copper tolerance in wood decay fungi. Copper is a major component in commercial wood preservatives as it is toxic to many wood decay fungi. However, certain fungi are copper tolerant and can attack preservative-treated wood, resulting in structural damage to treated wood members. Here we used large-field XFM to visualize six different elements (K, Ca, Mn, Fe, Cu, and Zn) in the mycelia and wood inoculated with four different species of brown rot wood decay fungi. Wood blocks were partially dipped into a solution of copper sulfate, exposed to fungi in malt extract agar petri dish assays for nine weeks, and then imaged and compared to blocks that were partially dipped in water. The blocks were imaged immediately adjacent to an end-matched control that was placed in malt extract agar petri dish assays for 9 weeks, but not exposed to the fungi so that the differences in the elemental distributions could be directly compared. The colonized wood and mycelia were rich in K, Ca, Mn, and Fe; however, the elements and the spatial distribution in the mycelia and wood differed across fungal species. The most interesting results were the maps showing the copper distribution. While three of the four fungi grew on the copper-rich region of the wood, only one species, Fibroporia radiculosa, dramatically reduced the copper concentration in the region of fungal growth.     

Pilzentwicklung in Fichtenholz unter Schutzgasatmosphäre

Fungal growth in spruce timber stored under low oxygen atmosphere . Fungal growth and species composition in Norway spruce timber (Picea abies) stored under an atmosphere with low oxygen concentration was monitored by isolation techniques. The results were compared with those from unprotected wood and from living trees. The role of potentially antagonistic fungi is discussed.     

Epiphytic lichen diversity in old-growth and managed Picea abies stands in Alpine spruce forests

In the last decades, a large body of literature has grown to evaluate the impact of forest management on epiphytic lichens in boreal coniferous forests. However, information is still lacking on coniferous forests of the Alps. This study compares lichen diversity between spruce forest stands of four successional stages: (1) young, (2) intermediate, (3) mature forests managed for timber production with a rotation cycle of 120–180 years, and (4) old-growth protected forests. The emphasis was placed on the occurrence of nationally rare and calicioid species (lichens and fungi traditionally referred to as Caliciales, known to be indicative of forest age and continuity). For each forest successional stage, four plots were selected. In each plot, 7 spruce individuals were surveyed for epiphytic lichens according to a standardised sampling method. Species richness increased from young to mature stands, while no difference was detected between mature and old-growth stands. This pattern was also confirmed for rare and calicioid species which are, however, more frequent in old-growth stands. Differences in species composition were also found between the different forest successional stages. Mature and old-growth plots slightly overlap, indicating that to some extent comparable lichen assemblages could be found in these stands. A nested pattern of species assemblages was found, old-growth stands hosting most of the species which were also found in stands belonging to the previous forest successional stages. Our results support the hypothesis that the management regime applied to spruce forests of the Italian Alps renders mature stands managed for timber production somewhat similar to old-growth stands as lichen habitat. However, we found a higher complexity in old-growth forests, and many species of conservation concern clearly preferred old-growth stands. In this perspective, a further prolongation of the normal cycle it is likely to be a most favourable conservation-oriented management to be recommended at least within protected areas and Natura 2000 sites, where conservation purposes should receive a high priority.     

Effects of metals and pH on in vitro growth of Armillaria ostoyae and other root and butt rot fungi of red spruce

Armillaria ostoyae, Perenniporia subacida, Resinicium bicolor and Scytinostroma galactinum, root and butt rot fungi found on red spruce, Picea rubens, were tested, in vitro, for their sensitivity to metals typically found in high elevation forest soils where red spruce grows. Rhizomorph production by A. ostoyae from woody inocula in soils from red spruce stands at three elevations at each of five mountainous sites in the eastern United States was inhibited completely in the mineral soil from all elevations at all sites, and was also reduced significantly in the organic horizon from the upper two elevations at three of the sites. Inhibition was correlated with concentrations of metal ions in the soil. Growth of rhizomorphs into an agar medium containing lead and other heavy metals was inhibited for isolates of A. ostoyae from red spruce, but not for an isolate of Armillaria gallica from sugar maple; aluminium inhibited rhizomorph growth of isolates of both species. Mycelial growth of all four root and butt rot fungi was inhibited by lead, aluminium and other heavy metals depending on the solubility and concentration of metal and pH of the medium; growth inhibition was usually greater at an initial pH of 3.5 than at pH 4.5. Metal ions inhibited radial growth of Armillaria species more than that of the other three fungi. Rhizomorph growth of Armillaria was inhibited more than radial growth. Because local spread of A. ostoyae occurs frequently by means of rhizomorph growth between near roots, increases in lead, aluminium and other metals in the forest floor may contribute to this fungus' scarcity in high elevation soils and reduced incidence of infection at these sites in the eastern United States.     

Optimisation of a two-stage heat treatment process: durability aspects

Heat treatment of wood at relatively high temperatures (in the range of 150–280°C) is an effective method to improve biological durability of wood. This study was performed to investigate the effect of heat treatment process optimisation on the resistance against fungal attack, including basidiomycetes, molds and blue stain fungi. An industrially used two-stage heat treatment method under relatively mild conditions (<200°C) was used to treat the boards. Heat treatment of radiata pine sapwood revealed a clear improvement of the resistance against the brown rot fungi Coniophora puteana and Poria placenta. Increasing process temperature and/or effective process time during the first process stage, the hydro thermolysis, appeared to affect the resistance against C. puteana attack, but the effect on the resistance against P. placenta was rather limited. Heat treated radiata pine showed a limited resistance against the white rot fungus Coriolus versicolor and process variations during the hydro thermolysis stage appeared not to affect this resistance. A clear difference between the resistance of heat treated Scots pine sapwood and heartwood against fungal attack is observed. Scots pine heartwood showed a higher resistance against C. puteana and P. placenta but also against the white rot fungus C. versicolor. Similar results were obtained when heat treated birch was exposed to brown and white rot fungi. Heat treatment showed an improved resistance against C. puteana attack, especially at higher temperatures during the hydro thermolysis stage. A clear improvement of the durability was also observed after exposure to the white rot fungus C. versicolor and especially Stereum hirsutum. Increasing the process temperature or process time during the hydro thermolysis stage appeared to have a limited effect on the resistance against C. versicolor attack. Heat treated radiata pine and Norway spruce were still susceptible to mold growth on the wood surface, probably due to the formation of hemicelluloses degradation products (e.g. sugars) during heat treatment. Remarkable is the absence of blue stain fungi on heat treated wood specimen, also because the abandant blue stain fungi were observed on untreated specimen. Molecular reasons for the resistance of heat treated wood against fungal attack are discussed in detail contributing to a better understanding of heat treatment methods.     

Chestnut Red Stain: Identification of the fungi associated with the costly discolouration of Castanea sativa

In Europe, fungal pathogens have reduced the overall productivity of sweet chestnut (Castanea sativa) stands and continue to threaten the economic viability of forestry operations. Chestnut Red Stain (CRS) in north‐eastern Spain, locally referred to as Roig, is capable of decreasing the market value of chestnut timber to the point of rendering chestnut coppices uneconomical. Despite its economic importance, the specific cause of this red discolouration is unknown. With the objective of verifying the presence of fungi within the symptomatic wood, and identifying the fungus or suite of fungi associated with the red stain, wood samples were collected and cultured from 37 stumps found in eight recently harvested stands in the Montseny and Montnegre‐Corredor Natural Parks. To separate the fungi associated with CRS from other species inhabiting the chestnut wood, the origin of each fungal culture was mapped in every stump. The fungi were isolated from cultures and identified by sequencing the ITS region. The results provide insight into the fungal community inhabiting chestnut wood and the potential cause of CRS; nine species were identified including two species known to cause decay in chestnut. One of them, Fistulina hepatica, appears to be a likely candidate for the causal agent of CRS. This is the first study reporting the fungi associated with CRS and opens the door to new epidemiological studies focused on F. hepatica.     

Identification of wood‐decay fungi and assessment of damage in log depots of Western Black Sea Region (Turkey)

The aim of this study was to determine and quantify the wood‐decay fungi found on logs of forest tree species (beech, oak, hornbeam, Scots pine and fir) stored in log depots located in six different provinces in the Western Black Sea Region of Turkey. Additionally, it was aimed to determine the natural durability of some important wood species against the most commonly detected wood‐decay fungi. Eighteen families, 31 genera and 45 species belonging to the division Basidiomycota were detected; Antrodia crassa was identified for the first time in Turkey. The abundance of Panus neostrigosus, Polyporus meridionalis, Trametes hirsuta, T. versicolor and Stereum hirsutumincreased significantly with the holding time of the logs (r = 0.99, 0.87, 0.53, 0.57 and 0.78, respectively, p < 0.05). The majority of the fungal species were detected on logs stored in depots for 4–6 years (66%). The percentage of fungal species found on the logs with a holding time of three years or less was 29%, whereas the percentage for those detected on logs stored for seven or more years was 31%. Among the wood species, the greatest number of fungal species (29) and highest amount of fungi (2,539) occurred on beech wood. Natural durability tests showed that T. versicolor caused the greatest loss of wood mass, with an average of 23%. Field studies and natural durability tests performed in the laboratory showed that beech wood lost the most mass among the timber species studied.     

Polyphenols in Acacia mangium and Acacia auriculiformis heartwood with reference to heart rot susceptibility

The heartwood of Acacia mangium is vulnerable to heart rot and this is the first study to investigate the role of heartwood extractives in its susceptibility. Acacia auriculiformis was compared with A. mangium because it is rarely associated with heart rot. The heartwood extracts of both species were dominated by three flavonoids (2,3-trans-3,4′,7,8-tetrahydroxyflavanone, teracacidin, and 4′,7,8,-trihydroxyflavanone), which were purified and identified by nuclear magnetic resonance spectroscopy. The latter compound has not been previously reported in A. mangium and evidence for melacacidin is also newly reported. The mass spectrometric (MS) behavior of these compounds is given, for example teracacidin does not form molecular ions by either electrospray ionization or atmospheric-pressure chemical ionization. The nature of Acacia tannins was compared to quebracho tannin (composed of profisetinidins) using oxidative cleavage to enable MS detection but a negative reaction was obtained for both, which suggests the Acacia tannins may also be of the 5-deoxy proanthocyanidin type. The concentration of flavanones was less when A. mangium heartwood was decayed but the amount of proanthocyanidins was only slightly reduced and therefore these compounds may be more resistant to degradation by heart rot fungi. We found that the total phenol content of A. auriculiformis was about fivefold that of A. mangium, and, while preliminary, this provides evidence for a role played by phenolic extractives in heart rot resistance of these Acacia species.     

Red Oak in Southern New England and Big-Leaf Mahogany in the Yucatán Peninsula: Can Mixed-Species Forests Be Sustainably Managed for Single-Species Production?

Complex mixed-species forests are the focus of conservation efforts that seek to maintain native biodiversity. However, much of this forestland is privately owned and is managed for timber income as well as for conservation. Management of these high-diversity forests is particularly difficult when only one tree species produces the majority of high-value timber. We examined the past and current management of two regions which have those characteristics: Massachusetts, USA, with red oak (Quercus rubra L.) as the key timber species, and Quintana Roo, México, with big-leaf mahogany (Swietenia macrophylla King) as the most valuable species. These regions have different ecological characteristics, forest ownership types, landowner income, and importance of timber in total income, yet the silvicultural approach (low-intensity selective cutting) is surprisingly similar, and is generally failing to provide the conditions needed for regeneration and growth of key species. In both situations, the reluctance to harvest low-value species and interest in minimizing forest disturbance complicates management. Successful balance of timber harvest and forest conservation may be an important factor in preventing conversion of these lands to agriculture or residential development, but socioeconomic conditions (property tax policies and landowner affluence) play an important part in the outcome.