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ŠUMARSKI LIST 3-4/2012 str. 32     <-- 32 -->        PDF

dynamic, biologically and spatially complex (Robinson et al. 2002). There are numerous factors in these ecosystems which determine the dispersal and spatial patterns of small mammals, such as the characteristics and connectivity of landscape elements, the presence and characteristics of barriers and the suitable habitat’s spatial arrangement (Kozakiewicz 1993, Peles et al. 1999, Romanowski et al. 2008). The probability of local extinction and recolonization depends on the level of isolation of single patches in a heterogeneous landscape (Den Boer 1981, Fahrig & Merriam 1985). Therefore the distances which animals are able to cover and by that the level of their isolation are very important factors in the maintenance of the isolated population. The knowledge of animal motion probability and the covered distances contributes to understanding the stability of the whole ecological landscape (Adler 1987, Kozakiewicz 1993, Ims 1995).
There are still numerous semi-natural riparian and gallery forests along River Drava in South Hungary, which have mosaic-like pattern. The importance of River Drava from the aspect of Hungarian and European nature conservation is ensured by rare and threatened habitat types. River Drava is characterised with dynamic bank-destructing, bank-building and shoal-creating activity resulting in a diverse range of habitats. River Drava, as an ecological corridor and a continuous system of habitats is threatened by human disturbance (e.g. gravel mining, timber harvesting, clear-cutting), although the whole river is the part of Duna-Drava National Park and NATURA 2000 network (Závoczky 2005).
In the present study, we examined the small mammal population of a floodplain willow-poplar forest lying by the River Drava, laying emphasis on the spatial distribution of dominant species. The study investigates (i) how much the relative proportion of single species differs within the small mammal community in the examined years on the floodplain area and (ii) what kind of difference can be experience in the habitat use of the dominant species.
Materials and methods
Materijal i metode
Study area – Područje istraživanja
Trapping lines were traced out in a willow-poplar floodplain forest (Salici-Populetum) by River Drava, close to the village of Vízvár (46°5’N, 17°13’E). The mean width of the river basin is 150–400 m and the depth of the riverbed is 3–5 m with a maximum of 12 m. Higher water levels and floodings are typical in May–June and October–November, while low water levels can be seen in late summer and winter. Therefore, the changing in water level dynamics is an important limiting factor in the survival of coastal habitats and plays an admittedly important role in the survival of terrestrial species living here. As a second zone of the coastal zonation of rivers and streams, azonal high forests are found in the deeper parts of the low floodplains on young alluvial soils. The water turnover of these soils is relatively balanced, due to the degree of soil compactness.
The canopy layer of the willow grove is usually partially closed (50–70 %), sometimes reaching 25 m height. The grove is mostly formed by white willow (Salix alba) but there are some substances where crack willow (S. fragilis) forms the consociation. The lower canopy layer has 5–30 % coverage and its height is 10–15 m. Next to the juvenile individuals of the white- and crack willow, other tree species – e.g. European alder (Alnus glutinosa) or the European white elm (Ulmus laevis) occur only rarely. Their shrub layer is mostly absent and if present it is very thin. The herb layer shows great variety, it is well developed and has a coverage rate of 60–100 %. A specific facies of mostly marsh plants forms in this level, including slender tufted sedge (Carex gracilis), greater pond sedge and blister sedge (Carex riparia, C. vesicaria), common marsh bedstraw (Galium palustre), water forget-me-not (Myosotis palustris) and common reed (Phragmites australis).
Trapping protocol – Protokol hvatanja klopkama
We captured the small mammals with live trapping through the examination and we used capture-mark-recapture (CMR) method with the same box-type live-traps (75x95x180 mm). Just like the traps themselves, the trapping technique was also alike in all sampling periods: bacon and cereals were mixed with aniseed extract and they were used with vegetable oil as bait. In line with the protocol we performed 5-night long trapping sessions, the traps were checked two times a day (7 am and 7 pm), and the traps were triggered during the day. For individual identification of the animals toe tattoo was used.