Incidence of Stem Rot in Forests Dominated by Betula pendula Roth in the Central Group of Regions of Krasnoyarsk Krai

Birch stands, dominated by Betula pendula Roth, are a common feature of boreal forests. Within the Krasnoyarsk (central) group of regions, they are concentrated in the taiga, subtaiga and forest steppe zones of actively managed forests, represented by stands of seed and shoot origin. The health and productivity of birch forests is often determined by the activity of wood-decay fungi, which leads to rot and decay in trees. The objective of the research is to evaluate the impact of stem rot on birch forests in the study area, with a focus on key ecological and silvicultural factors. The research methods employed included a reconnaissance survey of birch forests, a detailed forest pathology survey of forest stands on research plots (31 pcs.), comprehensive macroscopic diagnostics of stem rot, identification of xylotrophic fungi by basidiomes, integrated assessment of forest health, graph analytics and statistical data analysis. Stem rot has been identified in all birch forests in the study area. In shoot origin stands, the incidence rate has reached the stage of the disease center (i.e., more than 10% of trees are infected). The following wood-decay fungi have been detected on the trunks of living trees affected by rot: Fomes fomentarius, Fomitopsis pinicola, Inonotus obliquus, Phellinus igniarius, and Trametes versicolor. The infection typically infects trees via spores, finding entry through dying branches or mechanical and thermal wounds on trunks. In trees of shoot origin, stem rot is frequently transmitted via mycelium from stumps left after felling. This, in conjunction with diminished immunity, contributes to a substantially elevated incidence of stem rot in comparison to stands of seed origin. The research has not established a reliable correlation between the incidence of stem rot and forest stand characteristics due to the impact of human activity on birch forests (e.g., cutting, fires, tree injury). At the same time, no reliable connection has been established between the spread of stem rot and the stage of recreational disturbance. Trees of various sizes are affected by stem rot, usually proportional to their representation in the structure of the forest stand. The disease has a detrimental effect on the trees, which is clearly evident in the decline of forest health.