Ivan Pilaš

Phoretic mites of three bark beetles (Pityokteines spp.) on Silver fir

The species composition and abundance of phoretic mites of the bark beetles Pityokteines curvidens, P. spinidens, and P. vorontzowi on Silver fir (Abies alba) were investigated in 2003 at two locations (Trakoscan and Litoric) in Croatia. Stem sections and branches from A. alba trees infested by Pityokteines ssp. were collected and incubated in rearing cages. Bark beetles emerging from the stem sections and branches were examined for photetic mites. A total of ten mite species were documented for the first time as associates of Pityokteines spp. on A. alba. These included Dendrolaelaps quadrisetus, Ereynetes scutulis, Histiostoma piceae, Paraleius leontonychus, Pleuronectocelaeno japonica, Proctolaelaps hystricoides, Schizostethus simulatrix, Tarsonemus minimax, Trichouropoda lamellose, and Uroobovella ipidis. T. minimax was the most frequent phoretic mite of all the three scolytines and U. ipidis was also common, whereas, the other mite species occurred less frequently. The species spectrum and relative abundance of mite associates were similar for all three Pityokteines species. Another species, Pleuronectocelaeno barbara was commonly found phoretic on P. curvidens, captured in pheromone traps in 2005 at the location Litoric. Furthermore, two previously collected mite specimens from Switzerland, phoretic on P. curvidens, were identified as Nanacarus sp. and Bonomia sp. The records from Croatia and Switzerland in the present study increase the number of known mite associates of Pityokteines spp. from one previously documented species to 14 species. None of the phoretic mites found in the survey in Croatia appear to have the potential to be used for biological control of Pityokteines spp., although the feeding habits are unknown for many species recorded.

Observed Climate Change in Croatia and Its Impact on the Hydrology of Lowlands

The lowland forests of South-eastern Europe present the remains of large forest areas, strongly influenced by periodic flooding and shallow groundwater tables. Their natural hydrologic regime was throughout history continuously exposed to various negative influences such as intensive forest exploitation and hydro-technical activities Nowadays there are more indices of regional runaway of climate change, which have caused a lowering trend in the groundwater tables and more intense droughts. To attenuate past, present and future negative impacts on the hydrology of lowlands, the possibilities of water table management were assessed. In this study, the procedure of estimation of the historic state of waterlogging based on a comparison of relict morphological indicators of hydromorphic soils and the present state of groundwater tables were developed. According to this, major influences on groundwater tables such as hydro-technical objects and disturbances of forest stand structure were assessed.

Climate variability, soil and forest ecosystem diversity of Dinaric Mountains

The Dinaric mountains in Croatia present one of the hot spots of European biodiversity, possessing a very large number of species and hosting most endemics. The Dinaric mountains in Croatia strongly affect the climate of the Adriatic region, making a distinct boundary between the maritime and a continental climate. In this chapter, an overview of climatic conditions of the Dinaric area is provided, including observed climatic changes of temperatures and precipitation in the last century. Existing soil types were assessed and described, in particular with respect to soil-forming processes. The role of climate as a dominant factor of soil formation was evaluated in relationship to other factors such as lithology and topography. Also, the occurrence of a specific broad range of forest associations in Dinarides was presented. We examined the correspondence between forest vegetation, soil, and climatic properties in the Dinaric area. As a finale, some future, very possible scenarios of regional climatic development are presented as a serious hazard to the sustainability of natural forest resources. We determined the variety of soil types, ranging from soils that are characteristic for Mediterranean (on limestone) such as Terra rossa with intensive red color, calcomelanosols and calcicambisols in high karst, to soils characteristic for continental climate (on flint or silica) such as dystric cambisols and luvisols. The forest vegetation of the Dinaric mountains constitutes 54 diverse forest ecosystem types, encompassing specific combinations of soil and phytocoenoses. Existing ecosystems form nine broader groups, that is, bioclimates, which are typical for Dinarides.