Interpreting the effect of regional climate fluctuations on Quercus robur L. trees under a temperate continental climate (southern Romania)

To determine oak tree sensitivity to climate fluctuations as a precipitation predictor, we eliminated monthly climate data and computed the growth-precipitation correlation using mean daily values calculated in time intervals. Precipitation from March through May is the primary limiting factor in intra-annual tree-ring growth for Quercus robur L. in southern Romania. Bootstrap correlations between the residual series and monthly average precipitation showed a positive dependence (r = 0.4). Using CLIMTREG software and daily climate data, we obtained correlation values of (0.6) and a better understanding of on-going tree radial growth. We found that the oak growth process is active during two distinct periods in the study area, December 22th-February 10th (earlywood) and March 04th-June 13th (latewood). For the studied oak tree population, the correlation with climate was positive with respect to precipitation and negative with respect to temperature. This indicates that annual tree-ring formation was influenced by the precipitation regime and frequency and by the degree of drought. These results also indicate that different behaviours occur among the examined earlywood and latewood under the same climatic conditions, which were then analysed.