Conservation assessment of the butterfly fauna along the River Sava between Krško and the state border

Abstract

An inventory of butterfly fauna was carried out in 2008 within the southern part of the Ecological Important Area »the Sava River between Radeče and the state border with Croatia« with the aim of evaluating the most important areas for butterflies. Butterfly fauna was surveyed within a study area of 32 km2, using the transect method. Twenty-one combined habitat types were included in the transect lines, with a total length of 19.2 km. The following parameters were used to evaluate the conservation importance of the combined habitat types: species richness of the combined habitat type, population density of species in combined habitat type, total population density of combined habitat type, maximum population density of species in combined habitat type, number of species with maximum population density in combined habitat type, number of threatened species in combined habitat type and number of threatened species with maximum population density in combined habitat type. A total of 69 species of butterflies (38% of Slovene butterfly fauna) were recorded, 10 of which are threatened on national or European level. The most important combined habitat types for butterflies are extensively managed dry grasslands, abandoned dry grasslands, some types of semi-intensively used grasslands, some types of ruderal communities, and dry woodland rides and edges.On the basis of the distribution of the most important combined habitat types in the study area, four important areas for butterflies were designated, with a total area of 6.6 km2. They are important for preserving threatened species, ecological specialists and other rare or locally distributed species in the sub-pannonian part of SE Slovenia.