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

Diverse Interactions: Root-Nodule Formation and Herb-Layer Composition in Black Locust (Robinia pseudoacacia) Stands

The black locust (Robinia pseudoacacia L.) is the second-most abundant deciduous tree in forest plantations, and one of the most important invasive woody species worldwide. The species has a strong transformer capacity, especially expressed by its nitrogen enrichment effect caused by nitrogen-fixing bacteria living in its root-nodules. The aim of this study was to explore the mutually interacting factors of nitrogen-fixing root-nodules, site characteristics, and herb-layer composition of 28 North Hungarian black locust stands. In the herb-layers of the study sites, a total of 121 plant species were identified, representing a relatively low species richness. The studied black locust stands showed high variability both in their herb-layer compositions and root-nodule formation, but no clear relationship could be demonstrated between these characteristics. The PCA component with which the species richness and Shannon-Wiener diversity index were strongly correlated was negatively associated with all root-nodule parameters (number, surface area, and weight), supporting the biodiversity-reducing effect of black locust by its nitrogen-fixing bacteria. All of the root-nodule parameters were negatively correlated with the PCA factor predominantly determined by stand age, confirming that the root-nodule biomass decreases as time progresses.

The Properties of Black Locust Robinia pseudoacacia L. to Selectively Accumulate Chemical Elements from Soils of Ecologically Transformed Areas

The black locust Robinia pseudoacacia L. is a common species that originated from North America. In Europe, it is an invasive and introduced plant. Due to its low habitat requirements and ecological plasticity, this species colonizes new anthropogenically transformed areas quickly. This study investigated the chemical composition of selected tissues of Robinia pseudoacacia L. in five various habitats with different levels of anthropopression conditions in southern Poland. The presented research aimed to compare the chemical composition of black locust parts tissues (leaves, branches, and seeds) and the soil under its canopy. To determine the heavy metal contamination and enrichment in soil, the geoaccumulation index, enrichment factor, contamination factor, pollution load index, and potential ecological risk index were calculated. The results showed that all examined soils are considerably or very highly contaminated and the main heavy metals, which pollute the studied samples, are cadmium (1.3–3.91 ppm), lead (78.17–157.99 ppm), and zinc (129.77–543.97 ppm). Conducted research indicates that R. pseudoacacia leaves are the primary carrier of potentially toxic elements. Due to low bioaccumulation factor (BAF) values, it is clear that black locusts do not accumulate contaminants in such amounts that it would pose risk to its use in degraded area reclamation. The obtained results showed that R. pseudoacacia is able to grow in a wide range of habitats and could be applied for greening urban habitats and disturbed ecosystems caused by industry.