## Materials and Methods  
### Site Description  
Plants, soils, and geological bedrock investigated in this study originated from three abandoned mining sites in Slovakia, Central Europe (Pb-Zn deposit Jasenie-Soviansko, Ni-Co deposit Dobsina-Dobra nadej and Fe deposit Sirk-Zeleznik). The Pb-Zn deposit Jasenie-Soviansko (N 48\({}^{\circ}\)89\({}^{\prime}\)27\({}^{\prime\prime}\), E 19\({}^{\circ}\)44\({}^{\prime}\)15\({}^{\prime\prime}\)) is situated in the western Dumbier part of the Nizke Tatry Mts., 7 km north from the village Jasenie. The deposit consists of several old mining waste dumps, but orchids occurred only in the heap of the Emil adit, which is located at an altitude of 834 m a. s.l. _E. atororubens_ occurs mainly on a sharp slope of a mining heap with almost no moss or lower plants. Few orchids (_E. atorubens and P. bifolia_) grew on the horizontal part of the waste dump under trees (especially spruce, willow and birch) or above heap material covered with moss, lower vegetation, and trees. _E. atorubens_ was extremely widespread in the mining heap and more than 1000 individuals grew on an area about 500 m\({}^{2}\). Technogenic substrate is formed mainly of metamorphic rocks of the crystalline basement of the Tatric unit of the Western Carpathians (mostly orthogneisses and migmatites) with fragments of mineralized rocks and also partially ore veins. Parts of ore veins and hydrothermally altered rocks formed hydrothermal carbonates (siderite, dolomite, ankerite, calcite), quartz and baryte and the sulphides are represented mainly as tetrahedrite, galena, bournonite, pyrite, chalcopyrite and sphalerite [20; 21; 22]. At the sampling site of the orchid and the substrate, the size of the rock fragments was up to ~7 cm. _E. atororubens_ grew in a bright habitat, without the presence of other higher plants, mosses and lichens. The slope of the mining heap with orchids was oriented to the south (SSW). The Ni-Co deposit Dobra nadej in Dobsina is located in the Spissko-Gemerske Rudohorie Mts., in the central part of the Slovak Ore Mountains Mts. in the Inner Western Carpathians (N 48\({}^{\circ}\)84\({}^{\prime}\)31\({}^{\prime\prime}\), E 20\({}^{\circ}\)39\({}^{\prime}\)08\({}^{\prime\prime}\)). The mining heap is situated at an altitude of 807 m a.s.l. Orchids occur on the vertical part of a heap without vegetation but also in the horizontal part of a waste dump between low spruces and sparse low vegetation represented mainly by grasses. Samples of the orchid _E. atororubens_ and technogenic substrate were taken from the mining heap, where metamorphic rocks (phyllites, acidic metavolcanites and metasediments) dominate the Gemer superunit. Hydrothermal minerals were represented by siderite, ankerite, dolomite, quartz, hematite, Fe-Ni-Co sulphides, pyrite, chalcopyrite and minerals of tetrahedrite group [20]. Up to 4 cm was the size of the rock fragments at the sampling point of the plant and substrate. The lighting and botanical conditions at the site and the slope orientation of the mining heap were the same as in the locality Jasenie. The Fe deposit Sirk-Zeleznik (N 48\({}^{\circ}\)61\({}^{\prime}\)71\({}^{\prime\prime}\), E 20\({}^{\circ}\)10\({}^{\prime}\)54\({}^{\prime\prime}\)) represents a weathered zone of hydrothermal Fe deposit which is located in the Revucka vrchovina Highlands, 10 km west of Jelsava, near the village Sirk at an altitude 416 m a.s.l. Phyllites, limestones, metaryolite tuffites and metalaydites [23] occurred mostly at this deposit site. Orchids collected for research were found in the forest of a technogenic substrate with a frequent abundance of fungi and incomplete decomposed plant residues. This initial substrate was located between pieces of limonite-quartz iron ore \(\sim\)8-30 cm in size. No hydrothermal carbonates were present here. Orchids grew in a light deciduous to mixed forest, mostly on a horizontal part of a mining heap between moss-covered pieces of heap material. All individuals of _E.__potica_ grew in one place, in an area of \(\sim\)15 m\({}^{2}\).