The influence of temperature and precipitation on the growth of Sessile oak in the colder sites of the Djerdap area: First results

The first results of an analysis of the influence of temperature and precipitation on the growth of Sessile oak in the Djerdap area were obtained from two stands in colder sites. In the study of how various factors influence on radial (RW), latewood- (LW) and earlywood growth (EW) of the mentioned tree species, four methodological procedures were used: 1) correlations between three-month (seasonal) temperature and precipitation values and residual chronology, 2) correlations between monthly temperatures and precipitation and residual chronology, 3) so-called response functions and 4) correlations between the SPEI3 (integrated for 3 months) drought index and residual chronologies. A notable sensitivity of sessile oak to summer precipitation was observed, indicating that higher precipitation, particularly in July, is associated with larger growth increments and healthier trees. No significant influence of temperature on growth increments was detected, except for some correlations between seasonal (3-month) climate factors and growth. Similar to preliminary findings on the effects of precipitation and temperature on the growth of sessile oaks in warmer sites of Djerdap, a more pronounced climate signal is evident in overall radial- and latewood increments, rather than in earlywood growth. The results indicated that sessile oak trees on colder sites are significantly more resistant to the adverse effects of above-average summer temperatures than those on warmer sites in Djerdap, consistent with previous research conducted in Djerdap National Park.