European beech forests are the most representative tree species in the Italian forests covering about 10% of the entire forested area and about 17% of broad-leaved forests. European beech is one of the most ecologically and economically important tree species which is, like other tree species in Italy, unfortunately, also affected by extreme events such as heat waves and drought currently occurring in the European basin which are expected to increase in the future. Therefore, understanding how this species will respond to such events, by studying its past responses and identifying physiological survival strategies, is crucial.

There are contrasting information on how European beech behaves under heat and drought events. One school of thought considers European beech as a conservative species which reacts to heat and drought by closing its stomata to reduce water loss (but also reducing to some extent photosynthesis with the risk of carbon starvation). At the opposite, another school of thought describes European beech as an opportunistic species, that bets on soil water limitation to leave the stomata open but risking embolism. Unveiling and disentangling the yarn would lead to better management of this species in the future and their resilience capacity.

In the recent study by Puchi et al. "Contrasting patterns of water use efficiency and annual radial growth among European beech forests along the Italian peninsula" we tested both hypotheses by investigating the basal area increment (BAI), and the δ13C-derived intrinsic water-use-efficiency (iWUE, i.e. the cost of fixing carbon per unit of water loss) as predictors, in four different, apparently healthy, stands, along a transect in Italy. Four stands that differ for climate and soil water availability and age. Through autocorrelation analysis, aiming at determining potential first signals of drought effects as the one in 2003, we challenged these hypotheses. And indeed, BAI dynamics showed contrasting responses, for the same species, between northern and southern sites with the northern showing an increase in δ13C and iWUE and loss of resilience after an extreme event, indicating conservative water-use, while southern ones showed increased BAI and iWUE, and, thus, more opportunistic behaviour. 

The southern European beech demonstrates a notable resilience to climate change, likely due to its genetic predisposition towards adapting to challenging environmental conditions. Embracing this adaptive strategy could offer a promising approach to confronting the impacts of climate change and its associated extreme events.

Paulina F. Puchi and Alessio Collalti