Changes in the phenological development of lime tree under future climate conditions

Climate change affects ecosystems and biodiversity, and the phenological development of plants has been changing. In this paper, we focused on the beginning of the flowering of the lime tree (Tilia cordata) in urban and rural settings.  The long-term series were evaluated from phenological and meteorological stations of the Czech Hydrometeorological Institute (period 1923–2023). The trends (using the Mann-Kendall test) and Pearson’s correlation coefficients between the beginning of flowering and meteorological variables were calculated.  Climate scenarios SPP2 4.5 and SPP5 8.5 (ALADIN-CLIMATE/CZ) were used to predict future climate conditions for lime tree phenological development. The main finding of this research is that the beginning of flowering of the lime tree during the period 1923–2023 is negative, and it varies in urban and rural environments. The results express the most significant acceleration of the beginning of flowering of T. cordata by -0.227 day per year in urban area and by -0.119 day per year in rural area. Moreover, the study proved that the beginning of flowering of T. cordata closely correlated with temperature (the Pearson’s correlation coefficient is in the range from -0.498 to -0.508.), and the correlation with precipitation is significantly weaker in both environments. The increase in air temperature in June and July will be significant in the period 2081–2100 (by 1.5 °C). Based on these findings, we expect a further shift in the beginning of T. cordata flowering to earlier dates. A change in the beginning of lime tree flowering will also affect the course of the pollen season.