Historical disturbance regimes continue to influence forest structure and mortality in primary mixed-beech forests of the Dinaric Mountains

Disturbances are key drivers of forest structure and function, creating spatial and temporal heterogeneity across landscapes. Evidence shows that disturbance regimes are shifting with climate change, yet it remains unclear how historical disturbances continue to shape present-day forest structure, composition, and mortality. We combined dendrochronological reconstructions of disturbance over the past two centuries with repeated inventories from 133 permanent 0.1-ha plots in primary mixed- Fagus sylvatica forests in the Dinaric Mountains to investigate how the legacy of disturbance timing, severity, and frequency shapes contemporary forest structure and average annual basal area mortality. Our results showed that quadratic mean diameter increased with time since disturbance, peaking at ∼150–175 years. Canopy layer diversity, although remaining relatively high (>0.8), declined with increasing time since disturbance. Disturbance severity modestly reduced horizontal size variability. Neither beech nor fir dominance responded to disturbance history. Structural equation modeling revealed that time since disturbance and its interaction with severity continued to directly affect mortality. Disturbance effects explained 13.5% of the total deviance. Historical disturbances had persistent legacy effects on mortality, with the highest rates in recently disturbed (150 years) plots. The time–severity interaction identified a peak in mortality following recent very high-severity events, with average annual basal area mortality reaching approximately 9%. Mortality increased with larger quadratic mean diameter, declined with greater beech dominance, and rose under drier recent conditions. Together, these findings demonstrate that disturbance legacies shape forest structure and modulate contemporary mortality for centuries after disturbance, remaining detectable even amid emerging climate stress.