Reaction of silver fir (Abies alba) growing outside its natural range to extreme weather events and long-term increase in March temperature

Abstract

Silver fir trees grown outside their natural distributional range were intensively studied in terms of their adaptability to increased late winter temperature and extreme weather events. The main questions of the study are: what is the influence of March temperature increase on tree rings and is the further introduction of silver fir outside its natural range economically justified? A total of 268 cores of silver fir were obtained from 12 sites throughout north Poland, which were located outside its natural range. Next, standard dendrochronological and dendroclimatological methods were applied. The March temperature increase was investigated using the bootstrap running correlation option with a 25-year moving window. Response function analysis revealed that the studied trees were more sensitive to winter temperature than to precipitation. Hierarchical cluster analysis identified two distinct geographical regions of fir growth. The positive effect of high March temperature is observed in both regions. Trees from the northwestern Poland region recovered from an extreme cold period in the following year, whereas trees from northeastern Poland were more sensitive, and needed an additional year for recovery. The reason for the relatively fast growth recovery in northwestern Poland is the influence of the mild Atlantic and Baltic climates.