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Soft rot in CCA-treated utility poles in Sweden
1989 - IRG/WP 1398
Soft rot investigations of CCA-treated utility poles (Pinus sylvestris L.) have been conducted throughout large parts of Sweden during 1974-1985. The investigation included 179 utility poles of the State Power Board which had been used for 10-18 years in the different administrative regions from northern to southern Sweden. In addition, 193 telephone poles from the Östersund area and 218 from the Kristianstad area were studied after having been in use for 18-25 years. The soft rot fungi cause two types of attack in wood cells, namely cavities (Type I) and erosion (Type II). In this investigation, soft rot is reported only when cavities of Type I were found. Erosion (Type II) is more difficult to observe, particularly in early stages, and in addition is almost impossible to distinguish from certain other attacks of rot, such as white rot, which may have occurred during storage of the poles before impregnation. In western and central Sweden, minor attacks of soft rot were found after 10-12 years in State Power Board poles embedded in soil in arable land and meadows. Power Board poles in northern Sweden had minor attacks of soft rot after 16-18 years in arable land and also in forest land when embedded in soil. Poles used by the Telecommunications services, all embedded in stone, showed minor and only occasional attacks of soft rot at Östersund (northen Sweden), but considerably more soft rot at Kristianstad (southern Sweden). The Telecommunication poles had been in service up to seven years longer than the poles used by the State Power Board. The localization and spread of soft rot attacks in a pole can vary. There may be many reasons for this, including insufficient impregnation, leaching, etc. The soft rot attacks found in the Power Board poles are always minor and sporadic and none of the investigated poles can be said to imply any safety risk. The same applies to the Telecommunication poles at Östersund whereas those at Kristianstad demonstrated considerably more severe and more frequent attacks. The attacks of soft rot in the Telecommunication poles more frequently occurred internally, more often deeper in the sapwood than in the outermost parts.
H Friis-Hansen, H Lundström

Fungal and bacterial attack of CCA-treated Pinus radiata timbers from a water-cooling tower
1991 - IRG/WP 1488
Transmission electron microscopy of decaying CCA-treated Pinus radiata timbers from an industrial water cooling tower showed presence of a thick biofilm covering some areas of the wood. The biofilm contained various morphologically distinct forms of microorganisms embedded in a slime. The study provided evidence of the activity of soft rot fungi and tunnelling and erosion bacteria in wood cells. The extent of damage to wood cells due to microbial activity varied, combined fungal and bacterial attack having the most damaging impact.
A P Singh, M E Hedley, D R Page, C S Han, K Atisongkroh

A short note on fungal decay in K33-treated poles
1982 - IRG/WP 1169
Soft rot cavities and erosion of the lumen have been found in K33-treated Pinus sylvestris poles from the years 1956-66 by microscopic studies. Poor treatment quality has been proved for some of these poles. The microscopy showed an unusual pattern of attack, and pre-treatment decay is suspected but not yet proved. Sounding the poles and using the Pilodyn indicated decay, but poking did not. Quantification of the attacks was possible only by microscopic studies.
H Friis-Hansen

Degradation of the normal fibre walls of rubberwood (Hevea brasiliensis) by the tropical blue-stain fungus Botryodiplodia theobromae
1998 - IRG/WP 98-10286
Rubberwood was examined by light microscopy and transmission electron microscopy (TEM) after exposure to the common tropical sapstain fungus Botryodiplodia theobromae for four weeks to study hyphal colonisation of wood cells and to determine if this fungus also degraded lignified normal fibre cell walls in addition to the walls of non-lignified elements. Light microscopy revealed relatively large diameter hyphae to be abundantly present in parenchyma cells. The hyphae were also present in other types of wood cells, including fibres. TEM provided evidence of fibre wall degradation in the normal rubberwood in the form of lumen wall erosion (type-2 soft rot decay). These observations suggest that the ability of B. theobromae to degrade lignified wood cells walls should be viewed with concern when utilising rubberwood which has been severely sapstained, particularly after prolonged exposure to this fungus.
A A H Wong, A P Singh

Ultrastructural observations on wood-degrading erosion bacteria
1986 - IRG/WP 1283
G F Daniel, T Nilsson

Micromorphology of the decay caused by Chondrostereum purpureum (Pers.:Fr.) Pouzar and Flammulina velutipes (Curt.:Fr.) Singer
1988 - IRG/WP 1358
Two basidiomycetes, Chondrostereum purpureum and Flammulina velutipes, form typical soft rot cavities in hardwoods and softwoods. Cavity formation is prececed by T-branching or bending of hyphae penetrating the wood cell walls. The two fungi also cause erosion of the wood cell walls.
T Nilsson, G F Daniel

Importance of bacteria in the deterioration of archaeological woods
1995 - IRG/WP 95-10122
An electron microscopic study of archaeological woods from different sites and of different ages revealed that the woods had been attacked by erosion bacteria, tunnelling bacteria and soft rot fungi. Bacterial erosion appeared to be most widespread, and was present independently as well as together with tunnelling and soft rot attacks. Thus, in many instances bacterial erosion was the only type of microbial attack present. This work recognizes the important role bacteria play generally, and erosion bacteria particularly, in the deterioration of waterlogged archaeological woods.
Yoon Soo Kim, A P Singh, T Nilsson

Decay types observed in small stakes of pine and Alstonia scholaris inserted in different types of unsterile soil
1990 - IRG/WP 1443
The attack of various wood-degrading microorganisms occurring in mini-stakes of pine and Alstonia scholaris buried in various types of unsterile soil was studied. Attacks by white rot, brown rot, soft rot, erosion bacteria, tunnelling bacteria and actinomycetes were found. Soft rot occurred in all soils, whereas attack by white rot and especially brown rot and erosion bacteria was rare. The type of soil influenced the occurrence of attack by tunnelling bacteria and actinomycetes. The former were mainly associated with horticultural soils whereas the latter were associated with soils from coniferous forests.
T Nilsson, G F Daniel

Evidence for wood cell wall degradation by the blue stain fungus Botryodiplodia theobromae Pat
1994 - IRG/WP 94-10077
Botryodiplodia theobromae Pat., a world wide ubiquitous polyfagus sapstain fungus, was found able to destroy the cell walls of birch fibres (Betula verrucosa Ehrh.) but not Caribbean (Pinus caribaea var. hondurensis Barr. and Golf.) and Scots pine (Pinus sylvestris L.) tracheids. The fungus caused characteristic erosion of fibre cell walls similar to soft rot type 2; destruction of the S1 - S2 interface and delamination and degradation of the S2 layer. No attack of middle lamellar regions or birch vessel walls was noted.
O Encinas, G F Daniel

A light and electron microscopic study of decayed CCA-treated radiata pine (Pinus radiata) wood from a cooling tower
1994 - IRG/WP 94-10056
An inspection of an industrial cooling tower in New Zealand showed surface decay of 12 year old Pinus radiata wood panels treated with CCA preservative to a retention of around 15 kg/m³ of salt. Wood decay micromorphology typical of that caused by soft rot fungi, white rot fungi, 'stripy' and 'v-shaped' erosion bacteria and cavitation bacteria were all commonly seen using a light microscope (LM). Some evidence of the presence of tunnelling bacteria was also seen but was not as common. Soft rot was largely absent from the wettest regions sampled such as spray-line supports and side panels in close proximity to the spray lines, and erosion bacteria attack was the predominant type in these areas. Transmission electron microscopy (TEM) showed that unusual patterns largely consisting of troughs, depression and granulations in wood cell walls, were in most instances, almost certainly caused by erosion bacteria, but in others, tunnelling bacteria were also present. Several decay patterns seen under light microscope as matrices of fine troughs parallel and perpendicular to the cellulose microfibres were difficult to characterise in terms of previous classification but were also thought to have been caused by erosion bacteria. The distinction made by previous classification between patternms formed by erosion and cavitation bacteria needed to be questioned on the basis of observations made. Whilst the TEM showed that erosion and tunnelling bacteria were often present in close association within the wood cell walls, light microscopy suggested that, in the majority of section examined, all the types seen were clearly seperated by regions of undegraded cell wall. The observations underscore the importance of erosion bacteria in wood decay under the conditions of a cooling tower where in-service timbers are kept constantly wet by the spray from water sprinklers. Also of significance is the great diversity of decay types seen, in particular the presence of cavitation bacteria and white rot fungi has not previously been recorded for high retention CCA treated cooling tower timbers.
A P Singh, R N Wakeling, D R Page

Microbial decay of an archaeological wood
1994 - IRG/WP 94-10053
A light and transmission electron microscopic investigation of an archaeological wood was undertaken to determine the cause of its deterioration. The wood came from a bulwark constructed in early 1100 in the lake Tingstäde Träsk on the island Gotland in Sweden. The samples of the wood, which was identified as Pinus sylvestris, were taken from a depth of 0.85 m below the bottom level. The wood was found to be heavily deteriorated, and from the micromorphology of decay observed under light and transmission electron microscopes it was concluded that the wood had been largely attacked by erosion bacteria. The degradation of wood components was quite variable, some cell structures/types showing greater resistance than others. The S2 wall layer of axial tracheids, which formed the bulk of the wood, was degraded most. In comparison, ray tracheids appeared completely resistant. Other cell structures/types, such as pit borders of axial tracheids and ray parenchyma cells, displayed features that were intermediate between the extremes noted above. These features are discussed in the light of available information on bacterial erosion of wood cell walls and on chemical composition of these cell structures/types in pine wood.
A P Singh, T Nilsson, G F Daniel

Microscopic characteristics of microbial attacks of CCA-treated radiata pine wood
1993 - IRG/WP 93-10011
Light and electron microscopic observations were made of CCA-treated radiata timbers, which had been placed in service in a vineyard soil as supporting poles and as part of a house pile, to determine the cause of their deterioration. The house pile had failed in service after between 9 and 13 years and was of particular interest because decay was more severe in deeper regions than at the surface and attack was present up to 750 mm above the groundline. It was clear from transmission electron microscopy (TEM) that the predominant type of attack in the house pile was caused by erosion bacteria. The erosion patterns seen under the light microscope as troughs, pits and shallow depressions in the cell wall were almost certainly caused by erosion bacteria. However it was not entirely clear what had caused degradation patterns seen as fine channels under the light microscope. Soft rot was seen in outer regions of the post at the groundline but was very rarely seen in deeper regions. The vineyard posts had been attacked by tunnelling bacteria and soft rot. These studies demonstrated the importance of using both the light microscope and TEM in evaluating the cause of wood decay.
A P Singh, R N Wakeling

Degradation features of waterlogged archaeological compression wood
1998 - IRG/WP 98-10258
The degradation characteristics of waterlogged archaeological compression wood excavated in South Korea were examined by transmission electron microscopy (TEM) and confocal laser scanning microscopy (CLSM). Degradation of Pinus compression wood occurred mainly in the inner part of S2 layer. In contrast, the outer part of S2 layer remained relatively intact. CLSM and TEM showed the erosion type of bacterial attack to be dominant in the secondary cell walls of both severe and mild compression wood. However, in some cases middle lamella was also degraded, which suggests that other forms of microbial attacks, such as bacterial tunnelling, were also present. Bacterial erosion in the severe compression wood was mainly confined to the inner part of S2 layer whereas in the mild compression wood it also extended into outer part of S2 and the S1 layer. The extent of erosion correlated to the differences in the amount and distribution of lignin, particularly in the outer S2 layer between the severe and mild compression wood cells. These features are compared with the degradation of normal Pinus wood.
Yoon Soo Kim, A P Singh

Bacteria are important degraders of cooling tower timbers: New Zealand experience
1995 - IRG/WP 95-10128
Microscopic examinations of CCA-treated Pinus radiata timbers in industrial cooling towers in New Zealand showed bacteria and soft rot fungi to be primarily responsible for the decay of these timbers. Of these micro-organisms, erosion bacteria appeared to be most widespread, attacking wood cell walls independently as well as together with tunnelling bacteria and soft rot fungi. Tunnelling bacteria attacked wood often with soft rot fungi, and less commonly with erosion bacteria. Sampling of wood from different locations in the cooling towers inspected indicated erosion bacteria to be most tolerant of oxygen limiting conditions among the microorganisms which attacked the wood, as bacterial erosion was the only type of decay present in the wood constantly saturated with water. The evidence presented of the presence of widespread bacterial attacks of industrial cooling tower timbers in New Zealand is the basis for recognising bacterial importance in the deterioration of cooling tower timbers.
A P Singh, R N Wakeling

Bacterial degradation of Pinus radiata compression wood
1996 - IRG/WP 96-10153
An inspection of twelve year old, CCA-treated Pinus radiata wood from an industrial cooling tower showed extensive surface decay of wood. Electron microscopic examination of decaying compression wood indicated that compression wood cells were attacked exclusively by bacteria, which were of erosion and tunnelling types. As compared to the normal wood, compression wood appeared to be more resistance to the bacterial attacks present. The highly lignified outer S2 wall and the middle lamellae in the compression wood tracheids were resistant to erosion bacteria, and were only occasionally attacked by tunnelling bacteria. These observations are discussed in relation to the information available on the structure and chemical composition of compression wood.
A P Singh, R N Wakeling

Ingestion of wood-degrading micro-organisms
1991 - IRG/WP 4169
An ultrastructural study was carried out on the digestive tract contents of Limnoria lignorum, frass, gallery walls and surface structures of the animals. The purpose of the study was to determine whether wood-degrading bacteria, fungi and other microbes and/or wood degraded by these microbes were present in gut regions and therefore could provide indirectly a nutritional source for Limnoria. Both bacterial (tunnelling) and fungal (soft rot) degraded wood fragments as well as lysed microbes, extracellular slime and various other microbes (actinomycetes, diatoms) were found in fore, mid and hind gut regions. The range of microbes associated with wood fragments from gut regions were similar to those recognized either colonizing or degrading surrounding gallery walls or present on the external surfaces of the organism itself. Wood materials in the gut were highly fragmented and showed evidence for either extensive bacterial or soft rot attack, or surface and sub-surface evidence for carbohydrate removal. The major wood degrading bacteria attack noted was tunnelling bacteria as well as a form capable of cell wall dissolution of pine wood. Both bacterial types carried out extensive attack of pine wood fragments present in Limnoria tunnels. Lysed fungal hyphae, and soft rot hyphae associated with residual soft rotted wood fragments were also prominent. Gut regions of Limnoria lignorum lacked a natural resident bacteria flora, although numbers of characteristic Gram-negative active vesicle producing bacteria were represented in all gut regions associated with wood fragments. In hind gut regions a prominence of wood middle lamella regions was noted suggesting that these cell wall regions were more resistant to attack. Results indicate ingestion of bacterial and fungal degraded wood and its associated microflora. It is suggested that ingestion of microbial degraded wood could provide Limnoria with increased substrate assessibility and a greater surface area over which their enzymes could act. Associated bacterial and fungal breakdown products could also provide an important supplimentary source of nitrogen.
G F Daniel, S M Cragg, T Nilsson

Micromorphology of oak wood degraded by brown rot fungus Coniophora puteana
2000 - IRG/WP 00-10356
To characterize the degradation of hardwood by brown rot fungus, Coniophora puteana was incubated on the wood blocks of Quercus accutissima. For comparison, the same fungus was also incubated on the pine wood blocks of Pinus densiflora. In softwood, the shape of the wood cells and thickness of the cell appeared unchanged even the loss of birefringence in the affected areas. In contrast, oak wood decayed by brown rot fungus showed the erosion of wood cell walls from lumen towards the middle lamella. Complete degradation of cell walls including the lignin- rich middle lamella occurred in some areas of the oak wood cells. Degradation modes of brown rot fungus C. puteana in oak wood followed a typical white rot. The production of hydrogen peroxide was confirmed cytochemically by the deposition of cerium chloride in the degraded wood cell walls. However, Bavendamm test was negative to C. puteana. The present work suggested that hydrogen peroxide produced by brown rot fungus might be associated with not only the depolymerization of cellulose in softwood but also the degradation of lignin in hardwood.
Yoon Soo Kim, Seung-Gon Wi, Kwang-Ho Lee

Bacterial degradation of wood cell wall: A review of degradation patterns
1990 - IRG/WP 1460
Information from bacterial degradation studies of 60's and 70's was reviewed by Nilsson in 1982. The application of electron microscopy to this area in recent years has provided much useful information and has eliminated earlier scepticism among workers about the ability of bacteria to degrade lignified wood cell walls. Studies using transmission electron microscopy together with those employing 14C-labelled lignins have confirmed that certain types of bacteria have a capacity to degrade intact wood, including timbers which have high lignin or extractive content and are considered naturally durable. It has not been possible thus far to isolate wood degrading bacteria in pure culture and thus their physiology and taxonomic affiliations remain unknown. Laboratory studies using mixed cultures of these organisms and observations of decaying timbers from natural environments have shown the degradation to be of three main types on the basis of microscopic appearances of degradation patterns. The three types are: cavitation, erosion and tunnelling. These patterns and bacteria which produce them during their attack of wood will be described in detail.
A P Singh, J A Butcher

Micromorphological and chemical changes of archaeological woods from wrecked ship's timbers
1987 - IRG/WP 4136
Micromorphological and chemical alterations of sea-waterlogged woods obtained from the ship-wrecked materials which had been submerged in Yellow Sea for over 700 years were investigated. The woods were deteriorated in varying degrees by marine organisms depending on species and parts of the woods. Under the light and scanning electron microscope the morphological characteristics of deteriorated woods were granular in appearance, erosion troughs in S3, separation of secondary wall from compound middle lamella and hole formation. Destruction occurred preferentially in S2 layer, followed S3 and middle lamella which was hardly deteriorated. Chemical analysis showed that lignin was more and holocellulose was less in the degraded than in the normal wood. The ratio of extracts by alkaline compared to hotwater and that of holocellulose were also markedly lower. These results suggest that microorganisms decomposing carbohydrates were the primary agents causing deterioration of sea-waterlogged woods.
Y S Kim

Use of Confocal Profilometry to Quantify the Weathering of Wood
2009 - IRG/WP 09-20421
The methods that have been used to screen chemicals for their ability to prevent the weathering of wood involve assessing the loss in weight and tensile strength of treated wood veneers or measuring the rate of erosion of exposed and unexposed (masked) wood subjected to weathering. The erosion of wood during natural weathering occurs slowly and long exposure times are required to produce differences in erosion of masked and unmasked areas that can be quantified using optical microscopy. The erosion of wood can be accelerated using artificial accelerated weathering and by selecting low density wood species that erode quickly, but specimens still need to be exposed to accelerated weathering for 600 hours before reproducible differences in the erosion of masked and unmasked areas can be detected using optical microscopy. Accurate measurements of the erosion of materials can be made using confocal profilometry. We hypothesized that the use of confocal profilometry would make it possible to more accurately measure the erosion of wood during accelerated weathering and hence shorten the exposure time required to produce reproducible differences in the erosion of masked and unmasked wood in samples subjected to accelerated weathering. In this study we tested this hypothesis by using confocal profilometry to assess the erosion of western red cedar wood exposed to artificial accelerated weathering in xenon-arc and QUV weatherometers for 100, 250, 500 and 1000 hours. We also assessed whether erosion was affected by the size of the unmasked area exposed to artificial accelerated weathering. The erosion of wood specimens during artificial accelerated weathering increased with time as expected. Specimens exposed in the xenon arc weatherometer eroded significantly faster than specimens exposed in the QUV weatherometer. There was a positive correlation between the size of the unmasked area and the erosion of wood during artificial accelerated weathering. Our results confirm that confocal profilometry can accurately measure the erosion that occurs when western red cedar wood is exposed to only 100 (xenon arc) or 250 (QUV) hours of artificial accelerated weathering. We conclude that confocal profilometry is a faster, more accurate and less labour-intensive way of measuring the erosion of wood during accelerated weathering than optical microscopy. The implications of our findings for the development of surface treatments and preservatives that can maintain the appearance of wood exposed outdoors are briefly discussed.
Chunling Liu, P Evans

Simulation and Investigation of Wood Degradation by Erosion Bacteria in Laboratory Experiments
2010 - IRG/WP 10-20431
A Microcosm experiment was successfully set up to establish, monitor and manipulate bacterial wood degradation under low oxygen conditions. Sound pine sticks were placed in waterlogged sediment from a heavily decayed pine pile foundation site in Amsterdam. The system was subject to different gassing treatment regimes in order to investigate the role of oxygen in the bacterial degradation process of wood. In different treatments, microcosm head space was aerated with air, air + O2 or N2. As a fourth treatment the air aeration was combined with a vertical water circulation through the whole Microcosm. Some Microcosms were equipped with oxygen sensors (optodes) to measure the oxygen concentration during the experiment in different depths. Wood degradation was microscopically detected and a classification for low decay intensities was developed. It was found that bacterial wood degradation occurred in all treatments detectable after 150 days. The fastest rate of decay developed in 120 days and was most intense in the water circulated treatment. The used approach was successful in simulating bacterial wood degradation under reproducible laboratory conditions. The presented set up can be used as a base for further investigations regarding optimal living conditions of and preservation strategies against erosion bacteria. Further investigations, especially long-term experiments, are necessary to understand the complex interaction of the bacterial wood degradation. Therefore, it is important to test preservation strategies in the laboratory before using it in the real environments, which will be possible with such an experimental design.
J Gelbrich, E I Kretschmar, N Lamersdorf, H Militz

Micromorphological and chemical characteristics of waterlogged archaeological bamboos excavated from the Yellow Sea
2012 - IRG/WP 12-10785
Bamboos have widely used as documentation material in Far Eastern countries such China, Korea and Japan. In particular, bamboo slips as documentation material were extensively used even after the wide spread of paper in those countries. A large number of bamboo slips have been excavated from the shipwreck since 2009 in Korea. Understanding the cause of deterioration of ancient bamboos is crucial for developing technology of restoring artifacts of historical and cultural value. When compared to archaeological wood, it is very seldom to find the research work on the ancient bamboo artifacts. In particular, examinations on the waterlogged archaeological bamboo works are rare. The work presented is on bamboo slips which were excavated from a shipwreck. Various microscopical techniques and chemical methods were employed to characterize the waterlogged archaeological bamboos which had been submerged for more than 800 years in the ocean of Yellow Sea. Erosion bacteria were the most important degraders of waterlogged archaeological bamboo cell walls with occasional TEM images indicating presence also of bacterial tunneling. Chemical analyses showed that cellulose and hemicelluloses were extensively degraded with an indication that lignin was also degraded to some extent.
Mi Young Cha, Yoon Soo Kim

Preliminary evaluation of degradation patterns in wood samples from the Yenikapı shipwrecks
2013 - IRG/WP 13-10798
The uncovering of several shipwrecks during the excavation of the Marmaray Rail Tube Tunnel Project in Istanbul provides an important opportunity to evaluate waterlogged woods buried for centuries. Identification of these woods showed that a variety of species was used in the ships. One shipwreck (a galley) from the Yenikapı Marmaray was examined using electron microscopy. The micrographs revealed a wide range in the degree of deterioration in the samples. The results confirmed earlier observations that erosion bacteria and soft rot were the main degraders of waterlogged softwoods and hardwoods.
C Köse, A M Taylor