Are mixed forests more resilient to a warmer and drier climate? A review on adaptive forest management of beech-oak forests in Europe

Janisse Deluigi , Christoph Bachofen, Jürgen Bauhus, Florian Schnabel, Charlotte Grossiord

European forests are increasingly threatened by climatic extremes such as hot droughts, which impair their vitality and ecosystem services provision. Mixing tree species with contrasting functional traits and resource use, such as beech (Fagus sylvatica L.) and oaks (Quercus petraea (Matt.) Liebl., Quercus robur L., and Quercus pubescens Willd.) may enhance forest resilience and decrease vulnerability to climate change. However, high uncertainties remain on how to effectively manage these mixtures, and their implications for ecosystem services. Through a comprehensive literature review, we assessed the geographical distribution, tree functional traits, and species interaction dynamics of mixed beech-oak forests across Europe. We further described how these mixtures are currently managed and which ecosystem services they provide. We revealed that despite distinct differences in tolerances to shade, drought, and heat between beech and oak, their mixtures do not consistently enhance climate resilience, as outcomes strongly depend on local conditions and management practices. Managed beech-oak mixtures can provide a wide range of ecosystem services, but often require intensive, costly interventions to maintain optimal beech-oak proportions and forest structure. A more integrated research effort is urgently needed to unravel how environmental conditions, species interactions, and silvicultural approaches jointly determine the resilience and ecosystem multifunctionality of mixed beech-oak forests across Europe.