DIGITALNA ARHIVA ŠUMARSKOG LISTA
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2 and 3; same hold for other species, see Fig. 2) and was expressed as Simpson index of dominance: DS = ()2 (Odum 1977) In total, 2708 small mammal individuals of 9 species were documented on the study site. For this study, data were collected under criteria as to have sufficient spatial coverage to represent the dynamics of small mammal dominance of the given range or forest; the measurement protocols were consistent on the basis of the effort and methodology (snap trapping in spring and autumn; see Zejda 1991 for details). Rodents were represented by 6 species: yellow-necked mouse (Apodemus flavicollis), wood mouse (Apodemus sylvaticus), bank vole (Myodes glareolus), common vole (Microtus arvalis), European pine vole (Microtus subterraneus, and house mouse (Mus musculus). Insectivores included 3 species: common shrew (Sorex araneus), European pygmy shrew (S. minutus), and European water shrew (Neomys fodiens). For statistical analysis, only the data on yellow-necked mouse, wood mouse, bank vole and common shrew, as sufficient number of individuals, were used. For all species under study and year we calculated mean dominance index D (in %) for spring and autumn communities. Differences in dominance between various time periods of particular small mammal species were calculated by One-way Anova in Statistica for Windows. We assessed the long-term changes in relation to the moisture regime (MR) of the floodplain ecosystem. Variation in floodplain MR was measured by means of 2 variables: (1) the flow regime (FR) of the Dyje river and (2) the moisture balance (MB; Hadaš 2003). The FR is expressed by the sum of mean monthly discharges of the Dyje river for the period March–May and June–September in the area of floodplain forests in the section from Nové Mlýny to Břeclav. Moisture balance (MB) is based on the following relation (Možný 1993): MB = (Ra– Rn) – (ETPa – ETPn), where Ra is the monthly total of precipitation in the given year in mm, Rn is the long-term total of precipitation in the given month, ETPa is the monthly total of potential evapotranspiration in the given year in mm, ETPn is the long-term total of potential evapotranspiration in the given month in mm. The sum of MB is calculated for the period April to September. The potential evapotranspiration (ETPa, ETPn) is derived using an indirect method according to Thornthwait (Nosek 1972). Moisture balance showed decreasing tendency in time (see Fig. 1). Its dynamic was also influenced by summer „flash floods” but these time limited floods have not permanent effect on the plant and animal community as periodic spring floods. We calculated the coefficient of correlation (r) to describe the relationship between the MR and the spring and autumn species dominance of small terrestrial mammals of floodplains for particular years. The significance of the dependence is calculated according to simple linear regression. To assess the combined effect of the FR and MB in the growing season, multiple regression analysis was used. Periods were evaluated from a derived multiple linear regression model (MLRM) and significance value was obtained. Results Rezultati Changes in dominance were monitored in yellow-necked mouse as its population steadily increases its proportion in studied communities (Fig. 2). However, a marked increase in dominance was also noted in wood mouse. From the previous fragmentary occurrence in the 1970s, it increased its dominance after changes in the water regime in the 1980s (F = 9.82; p<0.01 between populations in period 1 and 2; Fig. 2). Later on, a decrease in the percentage proportion occurred evidently at the expense of the increase of a more dominant and aggressive yellow-necked mouse population. In bank vole, changes in the water regime became evident by the decline of dominance (Fig. 2). The most marked changes were in insectivores. The highly dominant species, common shrew, showed a rapid fall to roughly 1% of dominance after regulation measures have been introduced (F = 10.49; p<0.01 between populations in period 1 and 2; Fig. 2). During the first period from 1968 to 1972, the springtime correlation of MR with small mammal species dominance was significantly high only in bank vole (r = 0.67; significance value was 0.59). During the period under water regulation (2002–2006) in spring, the bank vole dominance was also positively influenced by MR (r = 0.86) and FR dynamics in the Dyje river (r = 0.87, significance value was 0.82). The lowland drying influenced the gradual decreasing dominance of the species. The summer dominance of common shrew (1968–1976) highly correlates with the FR dynamics (r = 0.91; significance |