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Chemical, light and electron microscopic studies were carried out on wood of Oriental beech (Fagus orientalis Lipsky) decayed by the white-rot fungi Pleurotus ostreatus and Trametes versicolor for 30, 60 and 120 days according to the modified European standard EN 113. Mass loss as well as lignin, cellulose and carbohydrate content were determined before and after fungal attack. There were no significant differences of wood mass loss and chemical composition between both fungi at the end of incubation. After each incubation period, small specimens were stained for microscopic studies. The micromorphology of fungal cell wall degradation was rather similar for both fungi. Both decreased the cell wall thickness to the same extent. The accumulation of hyphae as well as the rupture of cell walls was also similar. The occurrence of hyphae, cavities in the pits and vessel walls followed nearly the same patterns. The parenchyma cells were completely destroyed. Altogether, both fungi produced a simultaneous white rot in Oriental beech wood.

The effects of exposing specimens of Oriental beech [Fagus sylvatica subsp. orientalis (Lipsky) Greuter and Burdet] to the white-rot fungi Pleurotus ostreatus (Jacq.: Fr.) Kummer and Trametes versicolor (L.: Fr.) Pilát strain 325 have been studied concerning the mechanical properties and chemical composition in terms of carbohydrates, cellulose, and lignin. Biological decay tests were carried out in accordance with the EN 113 standard specifications for 30 and 120 days. P. ostreatus had nearly the same deteriorating effects on the mechanical properties and chemical composition as that caused by T. versicolor. High and significant correlations were found between some mechanical properties with chemical components; for instance, the correlation coefficient (R 2 ) between impact bending and carbohydrate content was about 0.96. The changes of components influence the various mechanical properties to a different degree. Incipient fungal decay caused severe changes for impact bending and carbohydrate loss. Several other properties declined at 120-day exposure time, such as the hardness, compression strength parallel to grain, and cellulose and lignin losses.

Fungal wood decay strategies are influenced by several factors, such as wood species, moisture content, and temperature. This study aims to evaluate wood degradation characteristics of spruce, beech, and oak after exposure to the white-rot fungi Pleurotusostreatus and Trametesversicolor. Both fungi caused high mass losses in beech wood, while spruce and oak wood were more resistant to decay. The moisture content values of the decayed wood correlated with the mass losses for all three wood species and incubation periods. Combined microscopic and chemical studies indicated that the two fungi differed in their decay behavior. While T. versicolor produced a decay pattern (cell wall erosion) typical of white-rot fungi in all wood species, P. ostreatus caused cell wall erosion in spruce and beech and soft-rot type I (cavity formation) decay in oak wood. These observations suggest that P. ostreatus may have the capacity to produce a wider range of enzymes/radicals triggered by the chemical composition of wood cell walls and/or local compositional variability within the cell wall.

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