Responses of Vegetation Stages with Woody Dominants to Stress and Disturbance During Succession on Abandoned Tailings in Cultural Landscape

Studies of ecological succession on tailing containments (abandoned sedimentation basins with waste deposited by a factory producing sulphuric acid from pyrite ore) near the village of Chvaletice (Eastern Bohemia, Czech Republic) were carried out since 1973 with increased intensity and complexity between 1986 and 2002 (Kovář 2004). Vegetation cover in its relationships to various factors has been periodically monitored up to now. The abandoned ore-washery deposit is characterized by relative strong toxicity of the sediment material (high heavy metal content) and fluctuations of the microsite conditions up to extreme values (pH, salinity, surface temperatures). Species richness and the courses of some ecological processes are influenced both by availability of plant diaspores (regional species pool) determined with the presence of adequate dispersal mechanisms (anemochory, zoochory) and by the seasonal moderation of environmental variables excluding stress non-tolerant species at extreme epizodes and enabling survival of resistant species during the competition. Long lasting existence of patches without any vegetation together with herbaceous types of stands and woody successional stages create mosaics on the surface plateau. The oldest tree stands (in average 20 - 30 years old) are predominantly formed by Populus tremula and Betula pendula, with minor admixture of Salix sp. div. (mainly S. caprea), Pinus sylvestris, Quercus robur or Cerassus avium, rarely Sarothamnus scoparius. The abundance ratio of two main dominants, aspen and birch, was changed for the benefit of the first one after the summer fire in extremely hot days. The effect of clonality on aspen regeneration and regrowth immediately after the fire disturbance was profitably manifested and it apparently facilitates the present state with aspen prevailing in the most forested tailing places at present, seventeen years after the fire. This fact supports the importance of clonal plant species role during primary succession.