Features of Scots Pine Mortality Due to Incursion of Pine Bark Beetles in Symbiosis with Ophiostomatoid Fungi in the Forest-Steppe of Central Siberia

Forest decline is a significant issue affecting critical ecosystem processes worldwide. Here, we describe mortality in Pinus sylvestris L. monitored trees caused by the inhabitation of pine bark beetles (Tomicus minor Hart.) symbiosis with ophiostomatoid fungi (Ophiostoma piceae (Munch) H. et P. Sydow) infection forest-steppe central Siberia. Stem sap flow (Q) and stem diameter fluctuations (dRc) were eight during seven consecutive growing seasons (2015–2021). In addition, microcore sampling every ten days allowed determination wood formation 2021 season. During 2020 2021, two cases Q termination recorded among trees, microcores revealing no cambium formation. Thus, seasonal onset matches beginning beetle dispersal period when they attack inhabit tree stems. The circumferential size began 10–12 after onset, massive into disturbance occurred 21–23 days, total cessation was observed 23–26 at beetle’s egg development phase. timing dRc directly coincides life cycle. phenology T. driven weather conditions, particularly cumulative air temperature (>0 °C).