Abstract
Common beech is one of the most widespread and important European tree species, widely used in timber industry and for energy production. Under specific set of complex factors, it facutatetivly develops false heartwood, which considerably decreases market demand and value of processed logs. Due to its properties, false heartwood is more susceptible to attack of wood decay fungi, which leads to further loss of wood quality and value. One of the most common fungi able to cause heart rot in beech is Meripilus giganteus, known for its spread in the basal parts of the tree, where it can affect most valuable sections of round wood. The aims of this study were to monitor the distribution of fungus and appearance of its fruiting bodies in research area, and to analyze the extent of fungus impact on shape and size of false heartwood and occurrence and length of rot in infected trees, while taking into account the observed stem damage as a possible influential factor. Fruiting bodies occurrence, life span and position on a tree were monitored during a six-year period. For trees with confirmed infection, stem damage was evaluated and appointed to one of four size classes. False heartwood shape and share in associated stem cross-section were observed and measured on 1–4 cross-sections per tree at different heights, and compared between infected and uninfected trees. If present, length of wood decay extent on butt-log was measured. The obtained results confirmed increased susceptibility of mature trees to infection, which seemed to occur mostly via roots from where mycelium spread into stem base. It was found that Meripilus giganteus has a significant impact on enlargement and change of FH shape from cloud- to star-like, up to approximately 5 m of the stem height, thus causing devaluation of the first assortments. The presence of rot was confirmed on the majority of infected trees, extending averagely 0.5 m into the first processed log, causing the loss of utilizable volume and thus the value of round wood. Stem damage category showed no significant effect on false heartwood or rot, supporting the prevailing impact of the fungus.
Highlights
Common beech (Fagus sylvatica L.) is one of the most widespread forest tree species in Europe, found longitudinally from the Cantabrian Mountains in the west to the Carpathians and Balkan Mountains in the east, and latitudinally from Sicily in the south to Sweden and Norway in the north, on the area of approximately 49 million ha (Magri 2008, Pretzsch et al 2015)
Fruiting bodies of Meripilus giganteus were found in 17 forest stands across the monitored area, on mature trees ageing between 99 and 133 years at the moment of the first notification of fungus, confirming the increase of common beech susceptibility to infection with age (Zmitrovich et al 2019)
Given that wood-decay fungi predominantly spread via basidiospores produced in fruiting bodies, it is plausible that M. giganteus has been present in these most affected stands for a longer period of time, cumulatively building up the inoculum and infecting more trees, meaning that with time it could spread in other subcompartments, where it was confirmed in lower numbers
Summary
Common beech (Fagus sylvatica L.) is one of the most widespread forest tree species in Europe, found longitudinally from the Cantabrian Mountains in the west to the Carpathians and Balkan Mountains in the east, and latitudinally from Sicily in the south to Sweden and Norway in the north, on the area of approximately 49 million ha (Magri 2008, Pretzsch et al 2015). It is extensively distributed in Croatia as well, occupy-. In Croatian forestry, common beech is expected to account for more than 35% of annual cut volume in the period from 2016 to 2025, with a total production of 11,213,479 m3 of processed logs and 13,372,351 m3 of fuelwood (Anon. 2016)
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