Changes in Chemical Structure of Thermally Modified Spruce Wood Due to Decaying Fungi

Abstract

Fungi play a critical role in the decomposition of wood and wood-based products in use. The ability of decaying fungi to cause degradation of polysaccharides and lignin in the thermally modified Norway spruce (Picea abies L. Karst.) wood was examined with pure culture decomposition tests in laboratory conditions using the brown-rot fungus Serpula lacrymans (Schumacher ex Fries) S.F. Gray and white-rot fungus Trametes versicolor (Linnaeus ex Fries) Pilat. Spruce wood samples were primary thermally treated under atmospheric pressure at the temperatures of 100, 150, 200, 220, 240 and 260 °C during 1, 3 and 5 h, whereby larger losses in their mass, holocellulose, mannose and xylose were achieved at harder thermal regimes. Meanwhile, the holocellulose percent content reduced considerably, and the percent content of lignin increased sharply. Spruce wood thermally modified at and above 200 °C better resisted to brown-rot fungus S. lacrymans than the white-rot fungus T. versicolor. Due to the decay processes, the mass fractions of holocellulose, cellulose and hemicelluloses were lower in those spruce wood samples in which thermal degradation was more intensive, with achieving the highest mass loss values after thermal treatments, after which the decay attacks were poorer or even none with the minimal mass loss values due to action by the brown-rot fungus S. lacrymans and the white-rot fungus T. versicolor. The mannose and glucose percent content in thermally–fungally attacked spruce wood was intensive reduced, e.g., by 17% to 98% in wood after thermal treatments at temperature equal and above 200 °C.

Temperature and Tree Size Explain the Mean Time to Fall of Dead Standing Trees across Large Scales

“…This interpretation is supported by abundant evidence that fire changes wood properties through heating and charring, which results in generally adverse effects on woody decomposition [144][145][146]. The heating-induced chemical changes of wood have been shown to lower moisture retention capacity [145,147], change wood chemical composition [144,145,[148][149][150] and lower nitrogen availability for decomposers [47,147,151]]. In response to these changes, fungi showed lower colonization rates and growth on affected wood, and the negative effects on fungal growth and wood decay generally increased with fire intensity as well as the duration of heating [144,145,148,152,153].…”

“…However, Figure 7 reveals that, all other factors being equal, the MTF response of DSTs killed by fire and mortality by other causes diverge markedly from a DBH of 25 cm, which might suggest that mechanical strength to resist breaking forces is more important than factors driving decomposition for DSTs killed by fire. This interpretation is supported by abundant evidence that fire changes wood properties through heating and charring, which results in generally adverse effects on woody decomposition [144][145][146]. The heating-induced chemical changes of wood have been shown to lower moisture retention capacity [145,147], change wood chemical composition [144,145,[148][149][150] and lower nitrogen availability for decomposers [47,147,151]].…”

Evaluation of Chemical and Morphological Properties of Spruce Wood Stored in the Natural Environment

“…The smallest changes occurred in the content of D-mannose and D-glucose. According to Vidholdová et al [ 78 ], the decrease in the content of saccharides of spruce wood is related to the action of wood fungi. For the further use of wood, it is important to know the degree of degradation of carbohydrates, because, for example, the content of glucomannan influences the strength properties of wood [ 79 ].…”

Effect of a Thermal Catalyst on Organosilanes Treatment to Improve Durability and Stability of Canadian Wood

“…There is also the possibility that the aluminum sulfate, being a thermal catalyst, had thermally modified the wood. It is reported that thermal treatment affects the chemical structure of the wood, mainly hemicellulose, which increases decay resistance [31]. This study did not investigate resistance to white rot fungi, as they are less common on softwoods, nor did it consider resistance to insects, which are less important in Canada.…”