Resilience of European beech forests (Fagus sylvatica L.) after fire in a global change context

The European beech (Fagus sylvatica L.) is one of the most ecologically and economically important tree species in Europe. Nonetheless, post-fire ecological processes in beech forests have only been marginally studied although they might become more important for forest management in the light of global climate change drought effects. Focusing on the Southern European Alps, where numerous forest fires have affected beech stands, we assessed temporal trends and detected factors that influence beech regeneration in beech forests burnt between 1970 and 2012. Beech regeneration was found to occur abundantly in fire sites of mixed burn severity, and often co-occurred with light-demanding pioneer trees (mostly Betula pendula Roth). These pioneers declined in abundance from 20 years post-fire onwards, whereas beech dominance increased. Beech regeneration density was best explained in regression models by the canopy of remnant trees and the abundance of competing ground vegetation. As fire-injured beech trees slowly die back, the canopy gradually opens, favouring beech recruitment for as long as decades, depending on the light conditions. In contrast, dense layers of early post-fire colonisers may delay beech regeneration for many years. Generally, single fire events favour beech regeneration except in areas where the burn severity is extraordinarily high.