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

Riparian trees in mercury contaminated riverbanks: An important resource for sustainable remediation management

Mining operations generate sediment erosion rates above those of natural landscapes, causing persistent contamination of floodplains. Riparian vegetation in mine-impacted river catchments plays a key role in the storage/remobilization of metal contaminants. Mercury (Hg) pollution from mining is a global environmental challenge. This study provides an integrative assessment of Hg storage in riparian trees and soils along the Paglia River (Italy) which drains the abandoned Monte Amiata Hg mining district, the 3rd former Hg producer worldwide, to characterize their role as potential secondary Hg source to the atmosphere in case of wildfire or upon anthropic utilization as biomass. In riparian trees and nearby soils Hg ranged between 0.7 and 59.9 μg/kg and 2.2 and 52.8 mg/kg respectively. In trees Hg concentrations were below 100 μg/kg, a recommended Hg limit for the quality of solid biofuels. Commercially, Hg contents in trees have little impact on the value of the locally harvested biomass and pose no risk to human health, although higher values (195-738 μg/kg) were occasionally found. In case of wildfire, up to 1.4*10-3 kg Hg/ha could be released from trees and 27 kg Hg/ha from soil in the area, resulting in an environmentally significant Hg pollution source. Data constrained the contribution of riparian trees to the biogeochemical cycling of Hg highlighting their role in management and restoration plans of river catchments affected by not-remediable Hg contamination. In polluted river catchments worldwide riparian trees represent potential sustainable resources for the mitigation of dispersion of Hg in the ecosystem, considering i) their Hg storage capacity, ii) their potential to be used for local energy production (e.g. wood-chips) through the cultivation and harvesting of biomasses and, iii) their role in limiting soil erosion from riparian polluted riverbanks, probably representing the best pragmatic choice to minimize the transport of toxic elements to the sea.

Lead and copper removal from sterile dumps by phytoremediation with Robinia pseudoacacia

In Romania, huge quantities of gangue material from the mining activity practiced in the past were improperly stored and led to the pollution of the environment. Thus, this work is framed to manage the sterile dump of the "Radeș" mine (Alba, Romania) through a 12-week phytoremediation process. The efficient use of Robinia pseudoacacia was studied through the implementation, at the laboratory level, of a phytoremediation experiment based on various variants prepared by mixtures of gangue material, uncontaminated soil, and dehydrated sludge. The prepared variants, all planted with R. pseudoacacia, were watered with tap water, potassium monobasic phosphate, and enzyme solution. The bioconcentration and translocation factors for lead showed values ˂ 1, which indicates a potential presence of an exclusion system for Pb or a reduced Pb bioavailability since the R. pseudoacacia accumulates high concentrations of metals absorbed on and inside the roots. For copper, both factors had values > 1 indicating the suitability of R. pseudoacacia to readily translocate copper into the epigean organs. In the investigated experimental conditions, the highest efficiency in the removal of copper (93.0%) and lead (66.4%) by plants was obtained when gangue material was not mixed with other materials and wetted with enzymatic solution.

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.

Effect of soil water-phosphorus coupling on the photosynthetic capacity of Robinia pseudoacacia L. seedlings in semi-arid areas of the Loess Plateau, China

Afforestation can improve soil erosion in the ecologically fragile areas of the Loess Plateau; however, the amount of water and phosphorus fertilizer that can promote vegetation survival is unclear, which hinders the improvement of the local ecological environment and the waste of water and fertilizer. In this study, based on field surveys, water and fertilizer control tests on Robinia pseudoacacia L. seedlings in experimental fields, and fitting CO2 response curves to R. pseudoacacia seedlings using a Li-6400 portable photosynthesizer, we measured their leaf nutrient contents and calculated resource use efficiency. The results showed that (1) under the same moisture gradient, except for photosynthetic phosphorus utilization efficiency (PPUE), light use efficiency (LUE), water use efficiency (WUE), carbon utilization efficiency (CUE), and photosynthetic nitrogen use efficiency (PNUE) all increased with increasing phosphorus fertilizer application. Under the same phosphorus fertilizer gradient, WUE increased with decreasing water application, and LUE, CUE, PNUE, and PPUE all reached the maximum at 55-60% of field water holding capacity. (2) Net photosynthetic rate (Pn) of R. pseudoacacia seedlings increased with increasing intercellular carbon dioxide concentration (Ci), and as Ci continued to increase, the increase in Pn became slower, but no maximal electron transport rate (TPU) occurred. Under the same CO2 concentration, Pn reached a maximum at 55-60% of field water holding capacity and phosphorus fertilizer at 30 gPm-2·a-1. (3) Leaf maximum carboxylation rate (Vcmax), maximum electron transport rate (Jmax), daily respiration (Rd), stomatal conductance (Gs), and mesophyll conductance (Gm) reached their maximum at 30 gPm-2·a-1 of phosphorus fertilizer. Vcmax, Jmax, and Rd reached their maximum at 55-60% of field water holding capacity; Gs and Gm reached their maximum at 75-80% of field water holding capacity. (4) The higher the soil phosphorus content, the lower the biochemical (lb), stomatal (ls), and mesophyll (lm). With the increase of soil moisture, lb and ls are higher, and lm is lower. (5) Structural equation modeling showed that water-phosphorus coupling had a less direct effect on Rd and a more direct impact on Gs and Gm. Relative photosynthetic limitation directly affected the photosynthetic rate, indicating that water and phosphorus affected the photosynthetic rate through relative plant limitation. It was concluded that the resource use efficiency and photosynthetic capacity reached the maximum when 55-60% of field water holding capacity was maintained, and phosphorus fertilization was at 30 gP m-2·a-1. Therefore, maintaining suitable soil moisture and phosphorus fertilizer levels in the semi-arid zone of the Loess Plateau can improve the photosynthetic capacity of R. pseudoacacia seedlings.

Relationships between Heavy Metal Concentrations in Greater Celandine (Chelidonium majus L.) Tissues and Soil in Urban Parks

Anthropogenic ecological ecosystems create favourable conditions for the growth of the nitrophilous medicinal species Chelidonium majus in six urban parks in Southern Poland. This study focuses on the concentrations of trace elements in the soils, leaves, stems, and rhizomes of greater celandine. The soil samples were taken only in the humus horizon (A), which averaged approximately 15 cm in thickness under the clumps of Ch. majus. Regarding the reaction, the soil samples tested can be described as slightly acidic (5.6-6.8 in KCl) to alkaline (7.1-7.4 in H₂O). Organic carbon content at all sites is high, ranging from 3.2% to 13.6%, while the highest total nitrogen (Nt) content is 0.664%. The average total phosphorus (Pt) content in all samples is 548.8 mg/kg (and its range is 298-940 mg/kg), such values indicating its anthropogenic origin. In terms of heavy metals, Zn has the highest content in the analysed soil samples compared to the other elements, and its range is from 394.50 mg/kg to 1363.80 mg/kg in soil. In rhizomes, Zn also has the highest values (178.7-408.3 mg/kg), whereas, in stems and leaves, it varies (from 80.6 to 227.5 and from 57.8 to 297.4 mg/kg, respectively). Spearman's rank correlation showed high correlations between the content of Pb, Zn, Cd, and As in the soil and rhizomes of Ch. majus. Despite soil contamination with Pb, Cd, and Zn, Ch. majus does not accumulate them in its tissues. However, the translocation of Hg and Cr from rhizomes to leaves was observed. The different concentrations of metals in each park result from the degree of diversity of the parent rocks on which the soil was formed.

Applicability of Point- and Polygon-Based Vegetation Monitoring Data to Identify Soil, Hydrological and Climatic Driving Forces of Biological Invasions-A Case Study of Ailanthus altissima, Elaeagnus angustifolia and Robinia pseudoacacia

Invasive tree species are a significant threat to native flora. They modify the environment with their allelopathic substances and inhibit the growth of native species by shading, thus reducing diversity. The most effective way to control invasive plants is to prevent their spread which requires identifying the environmental parameters promoting it. Since there are several types of invasive plant databases available, determining which database type is the most relevant for investigating the occurrence of alien plants is of great importance. In this study, we compared the efficiency and reliability of point-based (EUROSTAT Land Use and Coverage Area Frame Survey (LUCAS)) and polygon-based (National Forestry Database (NFD)) databases using geostatistical methods in ArcGIS software. We also investigated the occurrence of three invasive tree species (Ailanthus altissima, Elaeagnus angustifolia, and Robinia pseudoacacia) and their relationships with soil, hydrological, and climatic parameters such as soil organic matter content, pH, calcium carbonate content, rooting depth, water-holding capacity, distance from the nearest surface water, groundwater depth, mean annual temperature, and mean annual precipitation with generalized linear models in R-studio software. Our results show that the invasion levels of the tree species under study are generally over-represented in the LUCAS point-based vegetation maps, and the point-based database requires a dataset with a larger number of samples to be reliable. Regarding the polygon-based database, we found that the occurrence of the invasive species is generally related to the investigated soil and hydrological and climatic factors.

Long-Term Vegetation Changes and Socioeconomic Effects of River Engineering in Industrialized Areas (Southern Poland)

The exploitation of mineral resources associated with human mining activities leads to the degradation of both terrestrial and aquatic biocenotic systems. The drastic disturbance of water relations as a result of the relocation of the riverbed of the Biala Przemsza River (southern Poland) for coal and filler sand mining will lead to changes in plant ecosystems. The purpose of this study was to determine and compare the diversity and distribution of vegetation in the Biała Przemsza valley in sections of channel straightening with the old riverbed and areas undisturbed by engineering works against the background of land use in temporal and spatial aspects. The results of the ecological and phytosociological studies showed that the composition of flora and vegetation types varied. Within the transformed riverbed, anthropogenic mixed forests with species characteristic of different ecological systems are developing, whereas the non-regulated section of the river is overgrown by an alder riparian forest with an almost complete species composition for this plant community. The highest Simpson's biodiversity index was found in the anthropogenically disturbed section of the river (0.86), and in the undisturbed section, it was 0.83. Both sections of the river were dominated by species of the family Compositae, Poaceae, Caryophyllaceae, Rosaceae and Apiaceae. The diversity of the flora in the transformed sections of the valley is determined by the presence of mosaics and microhabitats, as well as the nature of the surrounding vegetation, which is reflected in the ecological requirements of the flora concerning light preference (moderate light [56.25%]), and almost 90% of the flora from the area of the regulated section of the valley develops on humus-poor and mineral-humus soils. Although this area has lost its original natural function, it is now valuable for selected economic and social functions, especially in highly urbanized regions.

Soil and Vegetation Development on Coal-Waste Dump in Southern Poland

As an anthropogenic element of urban landscapes, coal heaps undergo changes due to both natural and anthropogenic factors. The aim of this study was to determine the common development of soil under the influence of vegetation succession against a background of environmental conditions. Vegetation changes and soil properties were analysed along a transect passing through a heap representing a particular succession stage. It was found that changes in the development of vegetation were closely related to the stages of coal-waste disposal, where the initial, transitional, and terminal stages were distinguished. The mean range of pH (H₂O) values in the profiles was 6.75 ± 0.21 (profile 1), 7.2 ± 0.31 (profile 2), 6.3 ± 1.22 (profile 3), and 5.38 ± 0.42 (profile 4). The organic carbon (OC) content in all samples was high, ranging from 9.6% to 41.6%. The highest content of total nitrogen (Nt) was found (1.132%) in the algal crust and sub-horizon of the organic horizon (Olfh-0.751%) and humus (A-0.884) horizon in profile 3 under the initial forest. Notable contents of available elements were found in the algal shell for P (1588 mg∙kg⁻¹) and Mg (670 mg∙kg⁻¹). Soil organic matter content was mainly dominated by n-alkanes (n-C₁₁-n-C₃₄) and alkanoic acids (C₅–C₂₀). Phytene and Phytadiene were typical for the algal crust on the initial pedigree. The initiation of succession was determined by the variation in grain size of the waste dumped on the heap and the variation in relief and associated habitat mosaic. Algal crusts forming on clay–dust mineral and organic material accumulating in the depressions of the site and at the foot of the heap can be regarded as the focus of pedogenesis.

The Perception of Urban Forests in Post-Mining Areas: A Case Study of Sosnowiec-Poland

Sustainable development policy emphasizes, among other things, the role of green areas in urban space. This remark applies in particular to post-industrial and post-mining cities. One of the elements of shaping the sustainable development of post-mining cities is that forests are often anthropogenic forest ecosystems growing in previously mining areas, one of the most characteristic elements of their spatial development. This article examines the role of urban forests in the post-mining area in Sosnowiec, located in the core of the Katowice conurbation in southern Poland. This article aimed to show the social perception of forests in post-mining areas among the local community and the features of urban forests. The social dimension of the interaction between humans and the environment is related to the issue of urban planning. Research was implemented based on quantitative, qualitative (CATI survey), and cartographic methods. The results indicate the significant role of forests in post-mining areas depending on their location in the settlement areas in a post-industrial city. The research emphasizes that residents perceive forests in post-mining areas of cities as an essential and expected recreational space. Notably, half of them do not see any threats therein. It is also expected that these areas will be better developed for recreational purposes in the future.