Managing mixed stands can mitigate severe climate change impacts on French alpine forests

Climate change affects forest ecosystem processes and related services due to climate variability. These might affect ecosystem functioning, especially productivity. Regarding management issues, mixed stands are considered a relevant option to maintain forest cover and ecosystem services under climate change. However, the possibility to maintain these mixed stands with management actions with positive effects on forest functioning under climate change remains uncertain and deserves further investigations. Relying on a simulation-based study with a forest gap model (ForCEEPS), we thus addressed the following questions: (1) Are monospecific stands vulnerable to climate change? (2) Would mixed stands significantly mitigate climate change effects on forest productivity and wood production under climate change? (3) Would conversion to mixed stand management affect significantly forest productivity and wood production under climate change compare to monospecific management? In this study, we quantified potential climate change effect (using RCP 8.5 and present climate) and management’s effect in the French Alps, focusing on five species (Fagus sylvatica, Abies alba, Picea abies, Pinus sylvestris, and Quercus pubescens). We tested different scenarios, with various composition, structure, or environmental conditions, under climate change. These simulations showed that monospecific stands currently growing in stressful conditions would be vulnerable to climate change. Managing mixed stands or conversion from pure to mixed stands would make it possible to maintain higher productivity in the long term than monospecific stands, depending on the species and the sites considered. Our results will feed into discussion on forest management in the context of climate change.