Roads and highways represent one of the most important anthropogenic impacts on natural areas and contribute to habitat fragmentation, because they are linear features that can inhibit animal movement, thereby causing barrier effects by subdividing the populations adjacent to the roads. The study presented here aims to determine, to which extent roads act as a barrier, subdividing populations of three species of small forest mammals: bank vole, yellow-necked mouse and common shrew, and what is the relative importance of road width and traffic intensity on the barrier effect. The study was carried out at four 25 m long segments of roads, close to the city of České Budějovice. All segments crossed a forest. The capture-recapture method was applied to determine the crossing rates of animals. The traps were checked three times each day during four consecutive nights, in summer and in autumn. We found that: (1) roads strongly prevent crossing movements in all three studied species, (2) there are interspecific differences in road crossing rates, (3) species cross more often narrow than wide roads, (4) traffic intensity does not affect the crossing rates.
Development and survival of larvae of two predatory ladybird species, Harmonia axyridis (Pallas) and Coccinella septempunctata L. on hibiscus (Hibiscus syridis L.) trees was followed daily outdoors during four seasons. Data were analysed and stage-specific mortality in a stage-structured model was estimated using Manly's (1997) method. Subsequently, key factor analysis was used to determine the life stages in which the daily mortality was best correlated with the total mortality during larval life. Consistently with the results from the first two years, the larvae suffered the greatest mortality during the first and fourth instars. The k-values for these two instars were also best correlated with those for the whole larval life, especially in H. axyridis.
Soil samples were collected from the whole territory of the Czech Republic, and the presence of entomopathogenic nematodes from the families Steinernematidae and Heterorhabditidae was evaluated by Galleria traps method. Of the 342 samples studied, 53.8% were positive for entomopathogenic nematodes with only one positive for the heterorhabditid, Heterorhabditis megidis Poinar, Jackson ct Klein. 1987. Of steinernematid species, Steinernema kraussei (Steiner, 1923), Steinernema felliae (Filipjev, 1934), Steinernema affine (Bovicn, 1937), Steinernema intermedium (Poinar, 1985), Steinernema bicornutum Tallosi, Peters et F.hlers, 1995, and Steinernema sp. belonging to “glaseri" group were recovered. With several exceptions the nematodes occurred in all the ecosystems, subecosystcms and habitats studied. They were more frequently found in samples from tree than open habitats, from light than heavy soil, and their incidence was ubiquitous, rather than patchy. Dependence of entomopathogenic nematodes on insect incidence seemed to be elementary for both their incidence and abundance. The sampling sites with moderate to severe insect abundance were 66.5 % positive for nematodes while those with slight or no visible insect abundance only 15 %.