engleski

Secular variations of monthly severity rating on the Croatian Adriatic coast during the forest fire season

The Croatian Adriatic region is subject to seasonal wildfires that inflict serious damage on the already unstable Mediterranean system. Degradation of agricultural and forestland sites is particularly grave. Autochthonous forest vegetation has in part adapted to the occurrence of forest fires ; however, the problem is more complex. As a rule, forest fires trigger a number of adverse ecological factors. The first to occur is wind or water erosion. The vegetation structure and climatic and weather conditions are among the root factors that pose a greater or lesser risk of fire. The goal of this paper is to analyse monthly severity rating (MSR) estimates in the period from May to September, when the risk of forest fires is the greatest. MSR values are one of the results of the Canadian Forest Fire Weather Index System method. MSR estimates were made for the meteorological station Hvar (20 m a.s.l.), where meteorological data have been collected since 1867. Hvar is situated on the island of the same name in the central part of the Croatian Adriatic Sea. The results were compared with the coastal meteorological station Split– Marjan(122 m a.s.l.) during the period 1948– 2005. The analysis of the secular linear MSR trend for Hvar and the application of non-parametric Mann–Kendall rank test indicate a significant increase in MSR in June and July. The progressive test was used to obtain an increase in MSR, which began in the early 1980s and became significant at the beginning of the 21^st century. The MSR increase was even more distinct in Hvar in the short period of 1948– 2005. A significant MSR increase for Split– Marjan is observed only in July. One of the reasons accounting for increased MSR in July is attributed to a rise in extreme daily air temperatures. This is also confirmed by a rising linear trend of growing degree days (GDD) above the threshold of 20 ºC. The increase in GDD in Hvar became significant in the early 21^st century.

monthly severity rating ; growing degree days ; linear trend

Sažetak rada objavljen je u casopisu Forest Ecology and Management 234 (2006) (S) ; doi:10.1016/j.foreco.2006.08.280