Vegetation
of calamine soils

and its importance
for biodiversity and landscape
conservation
in post-mining areas

Project

You will find here a detailed description of the project and its research issues

What do we know about plants of metalliferous sites?

Ecosystems developing on soils that have been naturally or secondarily enriched in heavy metals have drawn strong interest from ecologists for a long time. Such ecosystems are sites of the occurrence of exceptional flora - plant species, varieties and ecotypes which under strong selection pressure have developed many morphological and physiological adaptations enabling them to survive in an extremely hostile habitat. These plants, sometimes called metallophytes, withstand not only the higher content and consequently high toxicity of zinc, lead, cadmium, copper, nickel and many other heavy metals but also the scarcity of nutrients and water.

Plant communities distinguished by the presence of metallophytes are rarely comparable. This is because the physical and chemical conditions of the substrata on which they develop are very diverse. Today most of the habitats suitable for these plants are of artificial origin; they are a by-product of the extraction and processing of metal ores. The characteristics of these habitats depend on the kind of ore, its chemical composition, the granulation of post-mining rocky material, the method of its deposition, and recultivation practices, if any. As a result, the development of vegetation in metalliferous areas proceeds in different ways depending on the existing conditions. The influence of the local flora, the small area of habitat patches, and the high degree of isolation increase this diversification.

The above-mentioned factors are responsible for the characteristic species composition of vegetation colonising post-mining areas, and they determine its uniqueness on a regional scale. Among the metallophytes there are many endemic and rare species having fragmented ranges or ranges limited to a few localities. The accompanying common species are usually varieties or ecotypes differing from the typical forms in that they have developed resistance to high concentrations of heavy metals in the soil. Their tolerance to metals is often genetically based.

For botanical research the most valuable localities are metalliferous areas rich in zinc and lead. They are localities of vegetation called calamine flora, after the ore called calamine. The richest and most interesting patches of this vegetation are found in only a few countries in Europe: Belgium, France and Germany. Similar plant communities apparently occur in Poland also, but they are poorer and their range is limited to the ore-bearing part of the Silesian-Kraków Upland (including the Olkusz Ore-bearing Region, OOR). Typical calamine species are lacking there, but other equally interesting metallophytes can be found. Among them are the extremely rare Biscutella laevigata (found in Poland only in the environs of Olkusz and in the Tatra Mountains), Arabidopsis halleri, which accumulates huge amounts of heavy metals in above-ground tissues, and also subspecies and forms of some common species (e.g., Armeria maritima, Cardaminopsis arenosa, Dianthus carthusianorum, Festuca ovina, Silene vulgaris) whose populations show exceptional resistance to extremely difficult physical and chemical conditions.

The described communities developed in the OOR area probably long before the appearance of man. Their natural habitats may be rock outcrops with galena and calamine deposits. Together with the discovery of these deposits (12th-13th century) and intensification of mining activity, the original localities of the flora of calamine soils began to decline. The direct cause was undoubtedly mechanical disturbance and destruction of the soil cover around the sites of ore mining. However, the metallophytes have survived and even spread thanks to the emergence of new secondary localities in abandoned excavations and on mine spoils.

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