Zane Striķe’s research while affiliated with Latvian State Forest Research Institute "Silava" and other places

With an occurring shift in the tree species distribution, European beech ( Fagus sylvatica L.) is becoming a perspective for forestry in the Baltics and Latvia in particular, despite presumed occurrence outside the natural distribution range. In 2023, a survey of European beech plantations established in 2020 in the central region of Latvia revealed that 13% of saplings had decline symptoms—branch dieback and top dieback in beech saplings, often accompanied by browning of leaves. An endophytic and anthracnose‐causing ascomycete, Apiognomonia errabunda, was isolated from shoots of symptomatic beech saplings and potentially associated with the observed symptoms. Accordingly, this is the first molecularly approved report of this fungus in Latvia.

Hybrid aspen Populus tremula L. × Populus tremuloides Michx. is fast-growing and a potential source of biomass for bioenergy production in Europe. However, knowledge about the phytopathological risks to hybrid aspen clones, particularly about frost crack damage as a possible infection gateway of fungal infections, is scarce. Five clones, represented by 205 trees from three trials in Latvia, were studied; two wood samples (at root collar and 1.3 m height) were obtained from each tree. Wood-inhabiting fungi were isolated and identified by the morphology and sequencing of the ITS region with fungal-specific primers, and fungal communities were compared using PERMANOVA. Fungal communities from trees with stem cracks were richer in species, especially pathogens, and species richness was higher in samples collected at 1.3 m height. Plant pathogens were isolated from 52% of all samples. Soft rot-causing Alternaria and Fusarium were dominant; Alternaria was more common at the height of 1.3 m, while Fusarium was more common at the root collar. White rot fungi were isolated from less than 2% of all samples, indicating a low degree of tree infection in the 15- to 16-year-old plantations. Clonal differences were not significant for fungal communities in general; nevertheless, for the occurrence of the genus Cladosporium, clonal differences were observed. In conclusion, the differences in fungal communities in relation to stem cracks implied only indirect clonal effects on phytopathological risks, emphasizing the resistance to stem cracking as a crucial trait for the sustainability of hybrid aspen plantations.

Key message After 5–6 decades since inflicting resin tapping wounds, overmature (> 120 years old) Pinus sylvestris stems remain undecayed and vigorous. Abstract Overmature trees of Pinus sylvestris bearing large wounds made by resin tapping decades ago are still present in woodlands of south-eastern Baltic Sea region. The aim of the present study was to investigate health condition of those trees focusing on fungal infections and to estimate impact of the injury on radial stem growth. The study was conducted in Latvia in three overmature stands of P. sylvestris , resin-tapped in 1950–1970 s. On the studied ninety 120–167-year-old trees, exposed sapwood constituted from 1140 to 7755 cm ² per individual stem. Of the 127 wounds sampled, 52 (41%) showed wood discoloration. The discoloration in its extent was limited, expanding beyond wound margins approx. 1 (max 3) cm in radial, and 6–7 cm in longitudinal directions. Of the 127 wood samples/wounds subjected to fungal isolations, 96% resulted in fungal growth, yielding 236 fungal isolates that represented 47 fungal taxa. The most common among macro-fungi was basidiomycete Porodaedalea pini , which was isolated from 9% of stems. The fungus is currently classed not as a tree pathogen, but instead as an indicator species for woodland sites to be considered for nature conservation. Data from tree ring widths have revealed that tree reacted to the resin tapping injury by increasing radial increment of the un-affected part of the circumference of the stem. Current study demonstrated that even on the long term, resin tapping has little influence on health condition and vitality of P. sylvestris , even at the very old age. This should be considered as a supporting message in case resin taping practices in the region are to be revived.