Age Structure and Disturbance Dynamics of Three Old-Growth Mixed Forest Stands in the Western Carpathians

Disturbances of different intensities are the principal drivers of natural forest dynamics. The widespread application of dendroecological methods in European research has yielded substantial evidence for the dominant role of large-scale disturbances in montane spruce forests; however, comparable analyses of disturbance regimes remain scarce for mixed beech–fir–spruce forests. Increment chronologies from 1-ha sample plots were used to reconstruct local disturbance chronologies in three mixed forest stands in the Western Carpathians. The boundary-line method was employed to reconstruct stand-scale disturbance regimes. The oldest trees in these plots reached 300–400 years of age. No evidence of stand-replacing disturbances was found. In most decades, growth releases occurred in fewer than 10% of the trees, suggesting that stand dynamics in these forests were driven by numerous events of limited spatial extent. Decades with higher proportions of trees showing growth releases occurred at each plot but were infrequent, and visual comparison indicated only limited temporal coincidence among the three studied stands. Spatial and temporal variation in disturbance intensity appeared to constitute an important mechanism facilitating the coexistence of species at the local scale. Wind-related disturbances were a plausible natural driver of some reconstructed disturbance episodes; however, there was also evidence of direct or indirect anthropogenic influence, particularly during the second half of the twentieth century.