The phenological seasons of Poland in the warming world.

The aim of the study is to examine the impact of climate change on plant phenology and the shift of phenological seasons. This paper considers phenophases of wild-growing plants in Poland at 36 observation stations over the past nearly 80 years. The analysis was conducted for two 15-year periods: a reference period (1946-1960) and a recent period (2007-2021), during which rapid global warming has been observed. This study applies the phenological calendar method. The results indicate shifts in the onset of successive phenological seasons in the recent period compared to the reference period, as well as in the duration of individual seasons. The most significant changes include (i) a shortening of winter due to an earlier onset of very early spring (by an average of 10 days across Poland); (ii) an advancement of subsequent seasons from early spring to early autumn, ranging from nearly 4 to more than 10 days, with the smallest shift observed for early autumn); (iii) a delay in the autumn onset by approximately 4 days; and (iv) a stable timing of winter onset throughout the entire study period. With regard to seasons length, in addition to the shortening of winter, an extension of the warmest phenological seasons was observed, with the greatest increase of 8 days for early autumn. Due to its location in the temperate transitional climate zone, Poland is characterized by high weather variability, which is reflected in substantial interannual variability in both the onset and duration of successive phenological seasons.Clinical trial registrationNot applicable.