The Hydrological-Hydrochemical Factors that Control the Invasion of the Black Locust (Robinia pseudoacacia L.) in Succession in Areas with Opencast Mines.

Studies on opencast mines have indicated that the spontaneous colonization of excavations and sedimentation tanks by vegetation is determined not only by the substratum and the land relief, but also by the hydrological and hydrochemical relations in the exploitation hollow. Sometimes, biological invasions can also disturb the natural revegetation. Robinia pseudoacacia L. black locust is an invasive alien species that frequently colonizes sandy habitats. Thirty study plots were randomly established on four types of sites: (1) sandy sediments, extremely dry places located mainly on heaps of post-washer slime; (2) sandy sediments, dry areas that are periodically flooded and have pulp; (3) clay sediments, damp areas that are periodically submerged, and (4) the control, a forest with R. pseudoacacia in its neighborhood. A total of 94 species of vascular plants and seven species of mosses were found. The vegetation at the sites differs and the role of the black locust increases along the dryness gradient and developmental phase of vegetation. Older phases of succession resemble a forest in the surrounding area. It is a R. pseudoacacia species-poor monodominant stand that has been forming for around 30 years. A lack of trees and dense grasses favor the successful invasion of the black locust on man-made sandy habitats.

Influence of Thermally Polluted Water on the Growth of Helophytes in the Vicinity of a Colliery Waste Tip.

The impact of thermal pollution of leachate from a post-coal mine heap on three macrophyte species: Phragmites australis, Typha latifolia, and Scirpus sylvaticus was examined over the entire vegetation season. Hydrological measurements showed that the temperature of the leachate was ca 50 °C at the site of leachate inflow and decreased to ca 15 °C at the end of discharge canal. The annual temperature and conductivity of leachate from the two control sites, a polluted water stream in the vicinity of the waste tip and an unpolluted stream, differ significantly. However, only the temperature explained the differences in plant traits. In April, and in some cases in May, plants in the leachate were significantly higher than in those on the control sites in terms of biomass and plant height. Thermal pollution caused a phenological shift in all species and also caused Scirpus plants to die out more quickly. Temperature also affected the proportion flowering vs. vegetative individuals, e.g., none of Scirpus plants started to bloom.