ABSTRACT:
To investigate the impact of climate change on growth and development of apples, phenological data from 17 Croatian stations in the period 19792009 were analyzed. Six different varieties of apples, three varieties of old-fashioned autumn (Bobovec, Canada and Kolačarka), two newer autumn varieties (Jonathan and Golden Delicious) and the earliest summer variety of Petrovača were analyzed. Eight phenological phases were observed. In the Croatian interior the growing season begins in the first half of April and ends in the first half of November. In the mountainous region of Croatia beginning of the growing season is shifted toward the end of April and ends in early November. The earliest vegetation was observed in coastal regions where the growing season begins in late March and lasts through the end of November. Analysis of linear trends of phenological phases of different varieties of apples indicate that climate change impact all apple varieties, and especially on earlier beginning of leaf unfolding and flowering in spring. Earlier beginning of leaf unfolding and beginning of flowering is the most expressed in mountainous region (36 days/decade). Although the beginning of the vegetation of all varieties of apples moved earlier in the spring, old fashion autumn varieties of apple ends their vegetation period earlier in autumn. It follows that its length of vegetation did not change significantly during the last three decades. Newer autumn apple varieties show greater sensitivity to change in length of growing period. It is noted shortening of vegetation period in the continental part and prolongation in the mountainous part of Croatia. Since the growing season in the mountainous region is the shortest related to the rest of the Croatia, the tendency of its prolongation indicate the possibility of favourable growing of apples in this region. To establish the impact of weather conditions on the beginning of apple flowering, into consideration were taken winter weather conditions during the winter dormancy of apples. Using Utah model we investigated the average chill units (CU) for different varieties of apple in different climatic zones in Croatia. Using Utah model it was for the first time evaluated what favourable or unfavourable area for growing apple is.
