Acknowledgements

• Figure 15C indicates the dependence of the occurrence of the studied species on the alkalinity of rocks in the vicinity of a locality (alcali). According to literature information, this species favors slightly acidic, as well as alkaline soils [30–32]. Clearly, this species mostly occurred in the soil type number 4 and prefers soils with high index of alkalinity between 0.25 and 0.4 mol/kg. This index is a ratio of different amounts of components in a

• Figure 15D shows the impact of vertical heterogeneity (vert\_het) on the probability of occurrence of P. bifolia. It is obvious that the probability of occurrence of the studied species increases with increasing level of vertical heterogeneity, so the species prefers

• In Figure 15E, the influence of habitat heterogeneity (KVES\_var) on the distribution of studied species is shown. The impact of this factor does not differ from the impact in the previous analysis—the species favors a higher heterogeneity of the environment and a

• Figure 15F indicates the impact of amount of arable land in the buffer zone of 250 m from particular orchid species (op\_buff) on the distribution of the studied species. As in the previous analysis, this species occurs more probably in the area with a low amount of arable land in a buffer zone of 250 m around the selected locality. The reason of this dependence was explained above. Out of all important factors from the Analysis 3, this

• Figure 15G shows the dependence of species distribution on the amount of solar radiation (solar\_rad). As it was said above, this species prefers shady places mainly in forests or

• In Figure 15H, the impact of reactivity of rocks in bedrock near the locality (reactivity) on the occurrence of P. bifolia is depicted. Clearly, the studied species occurs on rocks of type number 240 and 200. These numbers correspond to metamorphic rocks with high amount

The Maxent program is a useful tool for predicting potential distribution of species, not only for orchids. Based on the results of this study, the most important factors for both studied species were types of vegetation cover of land (consolidated layer of ecosystems; KVES), the amount of arable land in the buffer zone of 250 m from particular orchid species (op\_buff), and

Our results are very important and helpful in determination of new, yet unknown, localities of Dactylorhiza majalis and Platanthera bifolia, the endangered species of the flora of the Czech Republic. Without potential distribution maps, targeted searching of new localities, it would be only a random choice of orchid hunters. These results will help people interested in orchid

rock and corresponds to alkaline soils [34].

152 Selected Studies in Biodiversity

areas with different altitudes, as opposed to flat areas.

landscape structure with many different biotopes.

factor has the smallest impact on species occurrence.

of alkalinity such as dolerite, soapstone, or metagabro.

bushes, which are typical habitats of P. bifolia.

4. Conclusions

habitat heterogeneity (KVES\_var).

This work was supported by the Ministry of Education, Youth, and Sports of the CR within the National Sustainability Program I (NPU I), grant number LO1415.
