Change in Carpinus betulus flowering in the Czech Republic

Common hornbeam (Carpinus betulus) is one of the most important spring pollen allergens widespread in the Czech Republic. This study evaluates the changes in Carpinus betulus flowering and the length of the blooming period in the Czech Republic during 1991-2020. Temporal and spatial evaluations in the timing of the flowering and the length of the blooming period were investigated at different altitudinal levels. Moreover, the changes in mean air temperature and precipitation total in spring months (March-April-May) were assessed, including the correlation with phenological data. Geographic Information System methods, the Mann-Kendall test and Pearson's correlation coefficient were used for processing. The flowering of Carpinus betulus changed significantly over time during the 1991-2020 period. The linear models predicted early flowering in Carpinus betulus at different altitudes (27 days at > 701 m; 18 days at 501-700 m; and 13 days at 301-500 m) significantly (p<0.001) over the last three decades. Furthermore, the length of the blooming period of Carpinus betulus has been shortened (4 days) at the 301-500 m a.s.l. altitudinal level significantly (p<0.05). The strongest correlation was predominantly observed between flowering and the mean air temperature (March-April-May).