ABSTRACT:
When analysing the impact of climate variations on plants, an analysis should be made of perennial plants that grow freely in nature, without any agro-technical practice added. Forest trees and shrubs are particularly favourable for research. In phenology, a science which studies the regularity of periodical occurrences in plant development and animal behaviour, the common lilac is chosen as a reference plant. The common lilac can grow in almost every climate type and at high latitudes. As it can be found in all parts of Croatia, three development stages of the common lilac were considered: beginning of leaf unfolding, beginning of flowering and full flowering at 31 phenological stations in Croatia during the period 19612010. The beginning of flowering starts three weeks after the beginning of leaf unfolding and full flowering is reached one week after the beginning of flowering. In Croatia, the boundary of common lilac vegetation moves forward from the north to the south and from the west to the east. A comparison of a more recent period, 19812010, with the reference period 19612010 has shown that most phenological stations have negative deviation. That means an earlier beginning of leaf unfolding and flowering. To determine the effect of climate change on the development of the common lilac, the tendency of early/late phenophases was estimated using a linear trend, and the significance of the trend was tested by the Mann-Kendall rank test at a significance level of < 0.05. The results for the period 1961-2010 show that at most stations there is a significantly earlier beginning of flowering and full flowering of the common lilac (25 days/10 years). A significant increase in temperature indicates the impact of climatic changes on plants. The accumulated values of growing-degree days for the common lilac from one phenophase to the next are determined by a simple averaging method. Full flowering requires 300°C growing-degree days in continental Croatia, and double value (630°C) along the Adriatic coast and islands. So the common lilac has adapted very well to all climate zones in Croatia.
