Phenological fluctuations as a possible signal of climatic changes in the Croatian mountain area

Abstract

The phenological phases of some perennial plants (forest and fruit trees) and wild herbaceous plants as well as the stages of field work operations have been analysed at the Gospic mountain station during the available periods (mainly 1962-2004). The Gospic meteorological station was established at the end of 1872 and has the longest time series of observations in the Croatian mountain area.The results of the linear trend analysis indicate a significant earlier cutting of winter crops (3 days/10 years) and flowering (2-6 days/10 years) for plants which bloom in the second half of April and in May. Progressive analyses showed the beginning of earlier flowering phenophases in the middle or late 1980s, and these trends became significant in the mid-1990s. These variations are the consequence of a significant increase in winter and spring insolation and extreme air temperatures and a decrease in the number of freezing days. A significant positive trend in mean annual air pressure and negative trends in annual precipitation amount and the number of days with precipitation over 10 mm indicate a progressive growth in the persistence of dry weather in the Croatian mountain area.