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Coal is the most abundant fossil fuel in Europe, but the excavation of hard coal has covered large areas with disposed rock waste, and turned the natural habitats into disturbed novel ecosystems with harsh conditions differ in time and space. To examine the spontaneous complex successional gradient, we studied a large number of post coalmine heaps in Upper Silesia, which differ in vegetation type and age. Cluster analysis based on plant community composition (367 species in total) separated all surveyed plots on coal mining spoil heaps with herbaceous vegetation from Late Stage (LS) forests aged 14--56 years. Furthermore, the herbaceous vegetation was sub-grouped to three stages: Initial Stage (IS) aged 2--5 years, Early Stage (ES) aged 3--8 years and Mid-Stage (MS) aged 5--12 years. MS vegetation was characterised by the highest species richness and diversity (47 and 2.79) compared to ES (30 and 2.18) and IS (9 and 1.6), but higher species number and a similar diversity index occurred in LS (37 and 2.81). Functional diversity (FD) and community weighted mean (CWM) of nine functional traits showed higher (23.1) functional richness, higher (0.72) functional divergence, higher (4.5) functional dispersion, and higher value (24.4) of Rao's quadratic entropy in LS compared to those calculated from the first three stages. Species at the initial successional stage (IS) were characterised by lower canopy height, seed mass, higher lateral spread, and specific leaf area (SLA). Additionally, the lowest (0.22 mg CO2 per hour per square metre) soil respiration (Sr) rate was recorded from IS compared to (0.53, 0.82 and 1.00) from ES, LS and MS, respectively. The soil water content (SWC) was the most important factor affecting the soil respiration, while the soil temperature (St) did not follow the well-studied relationship between soil respiration and soil temperature. Our spatial and temporal analyses illustrated changes in plant community assembly processes in the course of spontaneous vegetation succession on post coalmine spoil heaps. The importance of trait mediated abiotic filtration in community assembly in initial-, early-, and mid-stages of succession with an increase in competitive exclusion at the late successional stage was emphasized. [ABSTRACT FROM AUTHOR]

Aims: Pioneer tree species such as Betula pendula and Pinus sylvestris encroach soils contaminated with heavy metals (HMs). This is facilitated by ectomycorrhizal fungi colonizing tree roots. Thus, we evaluated the ectomycorrhizal fungal (EMF) communities of B. pendula and P. sylvestris growing in HM-contaminated soils compared to non-contaminated soils. We also studied the effect of HMs and soil properties on EMF communities and soil fungal biomass. Methods: Roots of B. pendula and P. sylvestris were collected from three HM-contaminated sites and from two non-contaminated sites located in Poland. EMF species were identified using DNA barcoding. Soil fungal biomass was determined by soil ergosterol. Results: B. pendula and P. sylvestris growing in HM-contaminated soils had similar EMF communities, where Scleroderma, Rhizopogon and Russula as well as ectomycorrhizae of the long-distance exploration type dominated. Among all of the examined soil factors studied, toxicity index (TITotal) was the most significant factor shaping the composition of EMF communities. Despite significant differences in the structure of the EMF communities of trees growing in HM-contaminated sites compared to control sites, no differences in overall diversity were observed. Conclusions: Only well-adapted EMF species can survive toxic conditions and form ectomycorrhizal symbiosis with encroaching trees facilitating the forest succession on contaminated soils. [ABSTRACT FROM AUTHOR]

The restoration of soil fauna on a spoil heap is a strong indicator of successful reclamation. The studies were conducted on two types of materials: bare rock (BR) and BR with topsoil (TS) which were applied during coal spoil reclamation and three vegetation types. Four variants investigated included natural forest succession on BR (Succession_BR) and TS (Succession_TS), afforestation (Reclamation_TS) and afforestation with Robinia pseudoacacia (Robinia_TS). Soil pH, soil organic carbon (SOC) and total nitrogen (TN) content, and soil texture were measured in 0–10 cm layers. Earthworms were collected using hand sorting method, and enchytraeids were collected using wet extraction with the heating method. The investigated soil had varying pH values from 5.3 in a BR to 7.2 in Robinia_TS. The highest content of SOC and TN were in Successinon_BR, and the lowest was in Succession_TS. Enchytraeids density was in the following increasing order: 275, 2982, 3001 and 4548 ind m−2 for Succession_BR, Robinia_TS, Succession_TS and Reclamation_TS, respectively. Earthworm density ranged from 0 ind. m−2 in the Succession_BR through 116 ind m−2 and 120 ind m−2 in Reclamation_TS and Succession_TS, respectively up to 162 ind m−2 in the Robinia_TS. The reclamation treatment was a major driver for soil fauna development while vegetation type was of secondary importance. Investigated soil fauna was positively related to pH value and clay content. The most stimulating variant for the development of earthworms and enchytraeids was the application of reclamation with various tree species and the planting of Robinia pseudoacacia on the topsoil. [ABSTRACT FROM AUTHOR]