Effect of thermal activity on the differentiation of the vegetation of the “Ruda” postmining heap in Zabrze (Poland)

This paper presents the results of a study on the vegetation of the thermally active postmining heap "Ruda" in Zabrze (Poland). The aims of the study were: (i) to show the differentiation of the vegetation that has developed as a result of the thermal activity, and (ii) to determine the effect of thermal activity of the spoil heap on species richness and species diversity of the vegetation. Twelve plant communities were recorded on the heap. Thermal activity has a statistically significant impact on species richness (Z = 2.13, p = 0.03) and species diversity (Z = 2.29, p = 0.02). The species composition of plant communities reflects the habitat conditions, which are conditioned by thermal activity. As the distance from a zone with increased thermal activity increases, the degree of the spontaneous succession of vegetation and the complexity of the vegetation increase. Moreover, the share of annual species and kenophytes decreases in favor of perennial plants and apophytes. The number of plant communities (from four to eight), their species richness (number of species from 15 to 22) and species diversity (Shannon-Wiener diversity index from 1.81 to 2.19) also increase. A DCA analysis showed an increase in the shading, humidity and pH of the substrate, and the thickness of the dead organic matter within the gradient of the thermal activity.