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ŠUMARSKI LIST 11-12/2017 str. 20     <-- 20 -->        PDF

table, periodical floods etc.) created specific life conditions for communities of plants and animal species. However, regulation of the two rivers and construction of water networks during the 1970s have changed the water regime of forests. Changes in moisture conditions subsequently caused changes in characteristics of biocenosis. The most rapid and most flexible response was found in the herb layer, where the total biomass was reduced considerably (Vašíček 1991). The structure of the herb layer was shifted to drier herb communities which subsequently influenced insect communities (decreased species richness and diversity; Křístek 1991).
The community of small terrestrial mammals in a periodically flooded floodplain forest is characterized by high productivity (Zejda 1991). Although dynamic moisture regime of floodplain forests (high water table, periodical floods etc.) creates specific life conditions for communities of plants and animal species, most dominant species are well adapted to this environment. Small mammal individuals are forced to survive in refugia and the non-flooding parts during floods. Short period of inundation can be possibly survived by certain species in vegetation above the water level (Wijnhoven et al. 2005). Arboreal activity is known in all species of central European mice and the bank vole (Holišová 1969). The negative effect of flooding on their populations is relatively minor (Zejda 1976; Jacob 2003). The indirect effect of floods – which is the high primary production following the floods – has positive effects on their population density (Zejda 1991). The small mammal species (Rodentia, Eulipotyphla) are well known to be responsive to the variation in moisture in terms of changes in community structure and their monitoring can therefore be of bioindicative significance (Wijnhoven et al. 2005; 2006; Zejda 1976; 1985; 1991; Zhang et al. 2007).
In the presented study, we bring the long-term assessment of the effect of moisture conditions on the dominance structure of small mammals in floodplain forests of southern Moravia (Czech Republic). Based on detailed data from three periods (1968–1972, 1982–1987, and 2002–2006) covering a span of over 30 years, we highlight the influence of the moisture regime on the small mammal assemblage in a floodplain forest. We show that under lowered moisture conditions and reduced abundance of insects, the insectivorous mammals are among the most affected species, whereas the rodent community appears to be more resistant and respond less dramatically.
Material and Methods
Materijali i metode
The studied habitats are part of the largest preserved ecosystem of floodplain forests in central Europe. The climate of the locality is warm, dry to subhumid, with a mean annual air temperature of 9°C and a mean annual precipitation of 524 mm (Vašíček & Pivec 1991). The study area (120 ha of old forest) was situated near the town of Lednice at 164 m a.s.l. with coordinates 48º 48’ 30’’ N, 16º 47’05’’ E. This is a Research and monitoring site of Mendel University (Brno), part of the International Long-Term Ecological Research (ILTER) network. The study plots were located in a seminatural forest characterized by a group of forest types Ulmeto-Fraxinetum carpineum. It was originally a commercial forest (hard-wooded broadleaved stand about 100 years old in 1965 – at the beginning of monitoring), which was excluded from forest management and left as an experimental area for studying natural processes in forest ecosystems. Consequently, the forest is of natural character representing long term stabilized tree stands with minimal changes in tree stratum. The dominant species are: pedunculate oak (Quercus robur L.), common ash (Fraxinus excelsior L.), black poplar (Populus nigra L.), large-leaved linden (Tilia platyphyllos Scop.), and field maple (Acer campestre L.). In the shrub layer, following species occur most frequently: dogwood (Cornus sanguinea L.), European evonymus (Euonymus europaeus L.), European elder (Sambucus nigra L.), and also young trees of pedunculate oak, large-leaved linden, and field maple.
Herb layer of floodplain forests in the alluvium of the Dyje river were influenced by changes in the water regime as a result of constructing flood-control protection measures since 1972 (the absence of natural floods, decrease of the groundwater table). During the 1970s and 1980s, the forest was insufficiently supplied by water and began to dry. Herb layer composition changed during the study period from dominant Carex acutiformis Ehrh. and Rubus caesius L. to dominant Impatiens parviflora DC., Circaea lutetiana L. and Galium aparine L. The other common species were Urtica dioica L., Ajuga reptans L., Glechoma hederacea L. and Deschampsia cespitosa (L.) (see Penka et al. 1985; 1991 for detailed data).
Since the 1990s, forest revitalization measures, aimed at water regime improvement in the study area were undertaken. These resulted only in replenishment of groundwater level by means of channels (no periodically flooded forest), thus improving the water condition for deeply rooted trees of the forest (Hadaš 2003) having no effect on any changes in other forest environment. The long-term changes in water regime provide us with opportunities to investigate ecological changes in the floodplain forest and obtain data, which are necessary for its well-informed management.
Dominance of small mammals (Apodemus flavicollis AF; A. sylvaticus AS; Myodes (Clethrionomys) glareolus MG; Sorex araneus SA) was studied in three time periods (period 1: 1968–1972 period 2: 1982–1987, and period 3: 2002–2006) under various moisture conditions (i.e. AF1, AF2 and AF3 means dominance of Apodemus flavicollis in period 1,