DIGITALNA ARHIVA ŠUMARSKOG LISTA
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ŠUMARSKI LIST 11-12/2017 str. 23     <-- 23 -->        PDF

a real causal relationship between water regime and structure of small mammal assemblages.
After floods regulation, changes in the soil moisture, microclimate, herb layer composition, and in the community of invertebrates (Vaňhara 1986) affected the number of insectivores. For example, the species richness and densities of Carabidae and Arachnoidea decreased (Křístek 1991). These groups create the important source of food for Sorex species (Kolibáč 1995). The other protected insectivorous species Neomys fodiens disappeared from the plots (Zejda 1991). Sorex sp. are the dominant species in the Natural Reserve Jursky Sur – the largest swampy alder forest in Central Europe which is flooded 5 month of the year usually. By Pachinger (1982) and Pachinger & Haferkorn (1998), high level of moisture was positively influencing the dominance of insectivores.
Many plants requiring high moisture content declined both in numbers and tissue production. The greatest decline was that of the previously dominant Glechoma hederacea. Its dominance changed from almost 42 % of the herb layer cover at the initial stage to 5 % at time of flood regulation (Vašíček 1991). G. hederacea was, for example, one of the main diet items of the overcrowded population of bank vole (mean volume over 25%, Holišova 1971). Under conditions of the flooded forest, population of bank vole became regularly overcrowded (Zejda 1976). Under changed conditions, intervals of outbreaks prolonged similar to in the drier broadleaved forests (Zejda 1991). Also the spatial segregation due to competition with yellow-necked mouse may lower bank vole population (Grüm & Bujalska 2000; Horváth et al. 2012).
Yellow-necked mouse is a typical species of old forests with regular production of tree seeds. Good seed crop can strongly influence its abundance (Obrtel & Holišová 1974; Suchomel & Heroldová 2008; Bjedov et al. 2016). In our study good acorn crop was in the first period in 1969 in the second in 1982 and 1983, in the third in 2003. Oak growth covers 86% of the study area, of which 90 % are fruit-bearing trees. The influence of the seed years on overall small mammal dominance seems to be balanced.
Wood mouse eats greater variety of fruits and seeds, particularly seeds of shrubs, herbs, and grasses and for that ubiquitous species, changes in the phytocoenosis at the time when flooding period stopped (1982–1984) meant improvement in its trophic base (Obrtel & Holišová 1974). Wood mouse decline in the last study period may be influenced by the increased dominance of yellow-necked mouse, which is a typical old forest species (Hoffmeyer & Hansson 1974).
Results presented in this article indicate that changes in the MR can lead to changes in the dominance of selected species of small terrestrial mammals. These changes induce the chain of other changes related to important properties of the floodplain forest ecosystem, which markedly influence assemblages of small terrestrial mammals. For example also its diversity on our plots continually decreased in time. From H´ = 1.04 in flooded lowland (1968–72) to H´ = 0.87 in last research period (2002–2006; Zejda 1991; Suchomel & Heroldová 2004). By Crandall et al. (2003) flooding may increase the diversity of mobile vertebrates in affected areas by providing and renewing resources as it increase the variety and abundance of food.
As human influences continue in our research area, ecological stability of the natural formations should be ensured. Long-term study on the influence of MR on small mammal species in natural lowland forests would be of help in further management. It can be also applied to the management of other similar forest ecosystems under moisture changes.
Acknowledgments
Zahvale
This study was supported by financial means of the MSM 6215648902 and NAZV QH72075 projects. The work complied with Council directive 86/609/EEC regulations on experimental use of animals. English was improved by official SPI Publishing, professional editing services. The authors are very much obliged to Linda Bjedov for translation of English to Croatian.
References
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