Timing of phenological stages for apple and pear trees under climate change in a temperate-continental climate

The study examines the consequences of climate change in Malus (apple) and Pyrus (pear) on four phenological stages: bud swelling (code 51 BBCH Monograph), budburst (code 53), beginning of flowering (code 61), and end of flowering (code 69) in the temperate-continental climate of southern Romania. The hypothesis tested is how much the onset dates (TOD) of phenology stages moved earlier due to climate change. Weather and phenological data were collected from 1969 to 2018 and were statistically processed. There was an increase in air temperature (T) during the first 5 months in the year, with a significant rise in March and April; significant linear relationships show an advance in TOD with the years elapsed. Inverse linear relationships were found between TOD, maximum (T-max), mean (T-mean), minimum (T-min) temperature, and sunshine hours (Sh). The relationships between TOD and T-max were the strongest. The early stages of flowering phenology are advancing more strongly than later flowering stages. For apple, in the last 50 years, there was an advance of 13.8 days for stage 51, 14.8 days for stage 53, 10.7 days for stage 61, and only 7.3 days for stage 69; for pear trees, the advance was lower: 10 days for stage 51, 9 days for stage 53, 6.7 days for stage 61, and only 2.1 days for stage 69. These findings, which might be extrapolated to similar environments, have important consequences in fruit growing, like the occurrence of climate accidents due to late frost, insect pollination, and application of pesticides and irrigation water.