Natural Disturbance History Regime and the Development of the Dark Coniferous Forest in the Southern Sikhote-Alin

Age shifts in fir–spruce forests and the potential influence of ongoing climate changes upon them are pressing issues. The study focuses on a stand of undisturbed fir–spruce forest located in the southern Sikhote-Alin at an altitude of 530 m a.s.l. A permanent sample plot was established there in 2001, and a revision was conducted in 2022–2023 with wood samples (cores) obtained. The research has revealed significant deviations in the stand development from the previously described pattern of age shifts in virgin fir–spruce forests. Firstly, it was established that there have been no major stand disturbances over the last 242 years, and only minor ones occurring in 1831–1850 and 1931–1950 were identified. About 50% of Jezo spruce trees survived at least 2 minor disturbances during their development. Secondly, it is shown that Jezo spruce does not form a single-age generation within the studied stand. It was also found that at the time of revision, the stand was in a situation preceding a new stand disturbance. An important result obtained is that a stable trend of decreasing growth has been observed in 75% of Jezo spruce trees since 2001. This trend might not be associated with age shifts within the stand but could be attributed to the spruce’s response to global climate changes. Such a trend could significantly impact the age shifts in fir–spruce forest stands.