Grasslands of a Zn-Pb post-mining area (Olkusz Ore-Bearing Region, S Poland)

We studied the diversity of grasslands in the Olkusz Ore-bearing Region (OOR). The OOR area has been severely degraded by Zn-Pb mining and polluted with heavy metals originating from mine and industrial waste and from industrial emissions. We assessed the species composition and cover of vascular plants, mosses and lichens in 9 plots at each of 28 study sites on two types of substrate (sands and dolomite mining waste). In the 252 study plots we recorded 260 species. Only one species was common (Festuca ovina) and four were noted frequently (Rumex thyrsifl orus, Leontodon hispidus subsp. hastilis, Ceratodon purpureus, Bryum pallescens). Most numerous were species typical of calcareous, warm, dry habitats and mesophilous meadows; species characteristic of poor sandy habitats and fi elds were rarer. Metallophytes were also fairly often noted (e.g., Cardaminopsis halleri, Biscutella laevigata, Brachythecium albicans, Diploschistes muscorum). Grassland diversity depended on substrate type and land use history. Grassland of abandoned fi elds developed on fertile sandy soil was richest in species, with numerous meadow and weed species (Crepis biennis, Melandrium album). Grassland on poor sandy soil was poor in vascular plants but rich in lichens (Cladonia rei, C. monomorpha). Grassland on mining ore-bearing waste was rich in thermophilous and meadow species (Thymus pulegioides, Lotus corniculatus). Grassland on mining waste was fl oristically similar to the Armerietum halleri association of metalliferous areas of Western and Central Europe. It differed by the presence of Biscutella laevigata and the frequent occurrence of Rumex thyrsifl orus, Cardaminopsis arenosa, Gypsophila fastigiata, Potentilla arenaria and Anthyllis vulneraria. The OOR grasslands, especially those developed on mining waste, should be placed under legal protection, as they contain species that are rare and unique for Poland. These grasslands increase the biotic diversity of this post-mining region and form colorful islands on its landscape.