Publikasjoner
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2024
Sammendrag
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Forfattere
Ari Hietala Wilson Lara Henao A. Kolsgaard Simon Seljegard Nina Elisabeth Nagy Isabella Børja Tor Arne Justad Yngve Rekdal Even Bergseng Halvor SolheimSammendrag
Forest grazing by free-roaming livestock is a common practice in many countries. The forestry sector sees the practice as unfortunate owing to several reasons, such as damages inflicted by grazing in young plantations. Concerning Norway spruce forests, a tree species known to develop wood decay with high frequency followed from stem bark damage, there is a strong perception among foresters that the trampling damage caused by livestock on the superficial root system of this tree leads to decay. Because of the very limited scientific documentation available on this topic, we pursued a clarification by investigating three 38- to 56-year-old Norway spruce forests used for silvopasture. Two types of injuries were observed on exposed roots: bark cracks characterized by resin exudation, and injuries involving localized bark peeling and exposure of the underlying wood. These injuries occurred up to 250 cm away from the root collar, with the sector 50–150 cm away from the root collar showing the highest incidence of injuries. In two of the forest stands, wood within the injured root areas was primarily colonized by the wound parasite Corinectria fuckeliana or species of the order Helotiales, fungi that do not cause wood decay. Wood colonization of injured roots by Heterobasidion species, the most frequent wood decay fungi of Norway spruce, was common in the third stand, but only in a few cases it was possible to deduce that the colonization had probably initiated via trampling injuries on roots. In a few cases, an injury was located at stem base at the root collar height along paths used by animals, and in such cases, it was obvious that stem colonization by Heterobasidion species had initiated via the wound. The relatively small amount of data warrants caution when drawing conclusions. Considering the high establishment frequency of decay via stem bark wounds of Norway spruce observed in previous studies, our data would suggest that roots are generally better equipped to defend themselves upon infliction of superficial wounds than stem of this tree species. The likelihood of trampling injuries leading to decay may vary considerably between different stands, this presumably depending on the level of local propagule pressure by pathogenic wood decay fungi and the frequency of damages close to root collar.
Forfattere
Jorunn Børve Venche Talgø Juliana Perminow Andrea Podavkova lisa haugland Arne Stensvand May Bente Brurberg Rune Vereide Gaute MyrenSammendrag
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Sammendrag
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Sammendrag
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Sammendrag
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Forfattere
Jorunn Børve Katharina Pampus Tuuli Haikonen Andrea Podavkova Gaute Myren Roland W. S. WeberSammendrag
Ascospores discharged at rainfall and dispersed by wind can provide long-distance spread of the European canker fungus, Neonectria ditissima. Ascospores are produced by perithecia which are the sexual reproductive stage. Diffuse knowledge exists on the seasonal pattern of perithecium formation under different climatic conditions. Therefore, the development of perithecia was observed for several successive seasons at five sites in three Northern European countries. In Norway and Finland, ripe perithecia were commonly recorded throughout the year, and on individual cankers continuously for up to 28 months. In contrast, asexual reproductive structures (sporodochia) were confined to the growing season in both countries. In Northern Germany an average of 51% of cankers developed ripe perithecia by late winter, and perithecial senescence ensued in late spring. On average, ripe perithecia were present on cankers for 22 weeks. In contrast, sporodochia were observed all year round. The timing of perithecium maturation correlated with the number of days with > 2 mm rainfall in July–September. The presence of mature perithecia and sporodochia for different lengths of time in different countries has implications for regional disease management strategies.
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