Search

Wind is the leading disturbance agent in European forests, and the magnitude of wind impacts on forest mortality has increased over recent decades. However, the atmospheric triggers behind severe winds in Western Europe (large‐scale cyclones) differ from those in Southeastern Europe (small‐scale convective instability). This geographic difference in wind drivers alters the spatial scale of resulting disturbances and potentially the sensitivity to climate change. Over the 20th century, the severity and prevalence of cyclone‐induced windstorms have increased while the prevalence of atmospheric instability has decreased and thus, the trajectory of Europe‐wide windthrow remains uncertain. To better predict forest sensitivity and trends of windthrow disturbance we used dendrochronological methods to reconstruct 140 years of disturbance history in beech‐dominated primary forests of Central and Eastern Europe. We compared generalized linear mixed models of these disturbance time series to determine whether large‐scale cyclones or small‐scale convective storms were more responsible for disturbance severity while also accounting for topography and stand character variables likely to influence windthrow susceptibility. More exposed forests, forests with a longer absence of disturbance, and forests lacking recent high severity disturbance showed increased sensitivity to both wind drivers. Large‐scale cyclone‐induced windstorms were the main driver of disturbance severity at both the plot and stand scale (0.1–∼100 ha) whereas convective instability effects were more localized (0.1 ha). Though the prevalence and severity of cyclone‐induced windstorms have increased over the 20 century, primary beech forests did not display an increase in the severity of windthrow observed over the same period. Two main atmospheric patterns are driving European windthrow with large‐scale winter storms being more prevalent in Western Europe and summer thunderstorm‐generated winds being more prevalent in Eastern Europe. In central Europe, most forests display a mixed‐severity disturbance regime indicating that both large‐ and small‐scale disturbances are occurring. However, few studies have been conducted looking at the prevalence of large‐scale winter windstorms and small‐scale summer thunderstorms. Here we found evidence for both, but recently large‐scale winter windstorms have had a greater impact. Windstorms and convective instability drive primary forest windthrow damageTopographic exposure and time and severity of last disturbance moderate windthrowWindstorms create higher severity windthrow than convective instability Windstorms and convective instability drive primary forest windthrow damage Topographic exposure and time and severity of last disturbance moderate windthrow Windstorms create higher severity windthrow than convective instability