Tree growth and wood quality in pure vs. mixed-species stands of European beech and Calabrian pine in Mediterranean mountain forests

Mixed-species forests may deliver many forest functions and services more than monocultures, even because considered further resistant to disturbances than pure stands. However, few authors provided evaluation of the wood quality in pure and mixed forests. In this study, we analysed three sites occurring in similar environmental conditions in the southern Italian Apennines. The first two are pure stands, respectively dominated by European beech and Calabrian pine; the third refers to a mixed stand of both the previous species. We evaluated the tree growth trends and the wood quality through dendrochronological approaches and non-destructive technologies (acoustic detection), hypothesizing that the mixture can improve the fitness of each species and the related wood quality. A linear mixed model was applied to test the effects of exogenous influences on the Basal Area Index (BAI) and MOEd. Moreover, the Recruitment period was studied to verify if the wood quality is independent from the growth patterns. Results showed that the mixed effect influenced both the wood quality and the BAI. In the mixed stand, for each species, MOEd’s values were significantly higher when compared to the same species occurring in the pure stands. Moreover, the mixed effect aligned the MOEd values, making the wood quality uniform across the different diameter classes. In the mixed stand, a significant positive relationship between MOEd and Recruitment period, but also significantly higher BAI values, were found for European beech, but not for Calabrian pine. The study highlighted the need to favour the mixture among tree species, since it can improve both the forest yield and wood quality.