Knowledge about biotic (plant species diversity, biomass) and/or abiotic (physicochemical substrate parameters) factors that determine enzyme activity and functional diversity of the substrate on hard coal spoil heaps is limited. Spontaneously developed vegetation patches dominated by herbaceous species commonly occurring on these spoil heaps: grasses (Poa compressa, Calamagrostis epigejos) and forbs (Daucus carota, Tussilago farfara), were examined. The activity of dehydrogenase and alkaline phosphatase was twice as high in plots dominated by grass species compared with those dominated by forbs. Significant positive correlations were found between the activity of dehydrogenase and alkaline phosphatase with pH, available P, soil moisture, and water holding capacity and negative correlations between the activity of urease and soil organic carbon. Strong positive correlations were found between values for Shannon–Wiener diversity index, evenness, species richness and soil functional diversity in plots dominated by grasses. We found that the soil physicochemical parameters had a greater impact on enzyme activity of the substrate than plant biomass and species diversity. However, grasses, through their extensive root system, more effectively increased enzyme activity and health of the substrate than other herbaceous species, and as they stabilize the substrate and form dense plant cover, they can be recommended for reclamation purposes.

The relationship between the size of the particle fractions of the soil substrate and the diversity of the spontaneously developing vegetation was investigated on coal mine spoil heaps in Upper Silesia (Southern Poland). The analyses were based on 2567 research plots of developed spontaneous vegetation and their associated soil substrate samples collected from 112 coal mine spoil heaps. For each research plot the prevailing particle size fraction was determined (stones, gravel, sand, silt), the species composition and abundance was recorded and the species richness (S), Shannon-Wiener diversity index (H′), Simpson (C) and Evenness (E) indices were used to determine species diversity. From a total of 119 research plots (in all particle size fraction categories), the values of 15 physicochemical properties (pH, electrical conductivity, water holding capacity, moisture, carbon content, total N, available P, Mg and exchange cations Ca, Mg, K, Na, fine particles (%), gravel (%), stone (%)) were obtained to asses their impact on the floristic composition of vegetation patches using Canonical Correspondence Analysis (CCA). Additionally, functional traits of the dominant species of each vegetation patch (life forms, life strategies and socio-ecological groups), were selected to analyse their relation to substrate texture. It was shown that the highest species richness and the highest values for Shannon-Wiener diversity index, as well as Simpson and Evenness indices, were obtained in plots formed on stones. Moreover, the greatest variation in the participation of species representing different habitats, life forms, and life strategies was found on gravelly substrates. Contrary to our expectations, the vegetation diversity (in terms of both species and their functional traits) was not highest in habitats with a high composition of fine size particles.

The successful establishment of vegetation, soil development and biogeochemical cycling during the restoration process of mine tailings requires a diverse and metabolically active microbial communities. The objective of this study was to test whether there is any link between the functional groups of both the dominant plant species and soil microbial communities on unreclaimed coal mine spoil heaps of different age located in the Silesian Upland (Poland). At each sampling site the dominant plant species were recorded and characterised based on their Raunkiaer's life form, socio‐ecological group and their potential to form mycorrhiza. The functional diversity of the plant‐associated microbial communities was assessed using the microbial carbon‐utilisation guilds generated using the Biolog method. We observed no differences in the microbial functional diversity, but a gradual increase in the plant functional diversity with the age of the heap. Our results indicate that trees, plants with the potential to form ectomycorrhiza, and deciduous plants strongly affected the carbon‐utilisation profiles. The mean proportion of microbe guilds in dominant plant patches accounts for 60 % of the variance while the soil physicochemical parameters explained only 30 % of the variance. This suggest that in post‐industrial habitats the biotic features of the soil substratum are more important for the vegetation development than the abiotic parameters.

The history of coal mining in South Poland has left a legacy of many spoil heaps across the landscape. These have presented the opportunity to study their colonisation and spontaneous successional sequences over a long time period. We use the plant functional group (PFG) approach to characterize and compare species diversity on spoil heaps of different ages by utilising the ecological characteristics (PFG categories) of the species recorded during the course of spontaneous vegetation development. By changing species frequency into functional group frequency it was possible to find the significant differences in the functional composition of the studied vegetation and to analyze the dataset using non‐parametric statistics. There was a small increase in the number of species over time, while the frequency of geophytes, nanophanerophytes and megaphanerophytes increased significantly. A significant increase was also recorded for the frequency of competitors, stress‐tolerators and stress‐tolerant competitors and for native species. We found that the significant differences in species composition measured as PFG diversity occurred between the youngest and the oldest age classes. The PFG approach provided valuable insights into the nature of the species composition of the developing vegetation on hard‐coal mine spoil heaps. We suggest that it could be usefully applied in restoration practice in the future by facilitating the natural colonization of native species adapted to local conditions and thus retaining the local gene pool in these areas.