Food preferences of small terrestrial mammals and their influence on biodiversity of plant communities in wet orchid meadows

Food preference of small rodents to consume the roots of wild plants with the emphasize on their impact to bulbs of orchid Dactylorhiza majalis has been studied on three localities during years 2002 - 2007. There were selected ten couples of plants in each plots, one individual of couple plants was protected by tin triangle. Indicated plants have been measured in the beginning (high, length and wide of the leaves and flower number) and at the end of growing period (number of capsules). Small mammals were snaptrapped for three nights in the autumn. On each locality four rows of 25 snap traps were situated, two rows through orchid plots and two without orchids. In years 2004 {--} 2007 the food preference was ascertained on studied sites. Roots of Daucus carota (as a control in year 2004) and roots of Selinum carvifolia (as control in years 2005 - 2007) and roots of tested plant were put into one rectangle "bait" of size 15 x 6 centimeters from gauze. These 50 "baits" were placed among 100 traps on each locality, every other trap, during snaptrapped of small mammals. Browsing was classified by six number scale. During years 2005 - 2007 food preference of Microtus arvalis under laboratory conditions of Science Faculty of South Bohemia University was achieved with the roots of the same species as we used during food preference on plots. During years 2006 -2007 bulbs of Dactylorhiza majalis from laboratory condition and a few idividuals from endengered meadows by revitalization of pond were added. During yeas 2006 and 2007 the contain of stomach from Microtus arvalis and Microtus agrestis, catched during autumn, was studied. Bulb destruction by small rodents during years 2002 - 2007 was not confirmed. But Microtus arvalis preferred bulbs of Dactylorhiza majalis under laboratory conditions and roots of Selinium carvifolium and Lysimachia vulgaris boths in laboratory and wet meadows. Destruction of orchid bulbs and more preferred roots of wild plants by small rodents could occur probably only in outbreaks of their population cycle. I did not observe this on studied plots. In mount of stomach from Microtus arvalis only 3% underground supply organs of plants; rest of stomach contain was consisted of aboveground green part of plants. This result was expexted, because small rodents prefere during vegetation period green part of plants