The influence of climatic conditions on the tree-ring width of wild service trees (Sorbus torminalis L.) in Wielkopolska

The wild service tree (Sorbus torminalis L.) is a very rare tree species in Poland, where it reaches the north-eastern border of its natural range. The majority of this species’ stands is found in Wielkopolska. This study was aimed at examining the relationships between the growth and climate for trees of the species Sorbus torminalis L. growing in the Wielkopolska National Park and the Pniewy forest district (Wielkopolska). The samples for the analysis were taken from 63 trees. However, taking into account the missing growth rings and the difficult identification of the tree ring borders in sapwood, only ca. 30% of the samples could be synchronised and dated accurately. Applying the classic methods of dendrochronological dating, a 94-year STW chronology was constructed, spanning the years of 1920–2013. The chronology, in turn, was used as a basis for dendroclimatological analyses, including correlation, response function, and pointer years. The climatic data used in the analyses came from the meteorological station in Poznań; providing air temperature and precipitation for a period of 66 years (1948–2013) and 48 years of insolation data (1966–2013). Insolation had the highest negative impact and precipitation had the highest positive impact on the annual growth in May and June. Positive pointer years could be linked to humid months with low insolation during the growing season, while negative pointer years are characterised by deficient precipitation, a large number of sunny hours, and high air temperatures in the summer months.
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