Decay Assessment in a Hardwood Handrail at the South Bank, London

Abstract

A timber handrail made from the hardwood Keruing (Dipterocarpus spp.) and exposed in European Hazard Class 3 on railings at the Southbank, London was investigated to (i) determine the visual damage on the hardwood railing cappings quantitatively and to (ii) identify the causal organisms, and (iii) to characterise their decay patterns in the wood. The service life of this handrail of at least 25 years so far shows impressively that Keruing of this quality has exhibited a reasonable resistance to decay for the period. However, the selection of this timber for the construction may not have been ideal due to its large dimensional movement and the effect of this on the aesthetic appearance, in the form of extensive surface cracking, of several of the timber sections, including those rated as free from decay. The two principal decay organisms were identified as the white rot fungus Phellinus contiguus (Fr.) Pat. and the brown rot fungus Dacrymyces stillatus Nees:Fr. Decay patterns observed in the samples of the handrail and in invitro tests demonstrated the ability of P. contiguus and D. stillatus to cause a soft rot -like decay pattern in addition to their typical modes of action, i.e. white and brown rot. These results indicate that "classical" criteria in linking decay features to certain decay types and fungi can be much more complex than expected. Depending on the fungal species, a transition or switch mechanism between brown + soft rot and white + soft rot respectively is probable.

Correlation between anatomical characteristics of ethanol organosolv pretreated Buddleja davidii and its enzymatic conversion to glucose

“…The pretreated ground wood (approximately 5 mm particle size) was embedded in an acrylic resin (LR White) prior to sectioning, as previously described (Ray et al, 2005). The following embedding procedure was used: samples were fixed for 12 h in formalin-acetic acid-alcohol (FAA), which contains 63% ethanol, 4% glacial acetic acid, and 6% formaldehyde (from a 37-48% solution).…”

Effect of Physisporinus vitreus on wood properties of Norway spruce. Part 2: Aspects of microtensile strength and chemical changes

“…The term selective delignification is applied to a successive decomposition of the cell wall components by highly diffusible ecto-enzymes. Preferably, the degradation of lignin and hemicelluloses occurs at the beginning of fungal colonization, while the cellulose fraction is degraded at rather later stages (Liese 1970;Schwarze et al 1997;Martínez et al 2005;Ray et al 2005). Simultaneous rot is characterized by fungal ectoenzymes, which have the capacity to degrade cellulose, hemicelluloses, and lignin at the same time (Schmidt 2006).…”

Synchrotron X-ray micro-tomography imaging and analysis of wood degraded by Physisporinus vitreus and Xylaria longipes

“…White rot fungi cause a selective degradation of the cell walls. During early stages degradation of lignin and hemicelluloses commences, while the cellulose fraction is degraded at later stages (Pandey and Pitman, 2003;Ray et al, 2005;Schwarze, 2007). Microscopic investigations show that incubation of Norway spruce with P. vitreus also results in a preferential degradation of pit membranes and delignification of the secondary walls, while the main avenues of the hyphal growth in the xylem are along the xylem rays and tracheids (Schwarze, 2007;Lehringer et al, 2010Lehringer et al, , 2011.…”