Reclaimed Mine Sites: Forests and Plant Diversity

The relationship between vegetation and selected soil characteristics in different monoculture forest types was investigated as part of a landscape restoration project after brown coal mining. Six forest types were selected: alder (Alnus sp.), spruce (Picea sp.), pine (Pinus sp.), larch (Larix sp.), long-term deciduous forest (Quercus robur, Tilia sp.), and forest created by spontaneous succession. These stands were classified into two age categories (younger and older). The soil attributes, C/N, TC, TN, pH, and A horizon depth were assessed. The observed species were categorized into functional groups by life history, life forms according to Raunkiær, and affinity to the forest environment. C/N ratio, humus thickness, and canopy cover were the main soil parameters affecting plant communities. The highest C/N values were recorded in Pinus and Larix stands, which were significantly different from deciduous and succession stands. The highest diversity index was noted in younger stands of Alnus and the lowest in younger stands of Picea. Intermediate values of the diversity index were achieved in successional stands at both age levels and in Larix and Alnus stands. The species belonging to a functional group was not an important factor in these habitat types. The species composition and vegetation change over time in the Alnus, long-life deciduous, and Larix stands show that these species are more suitable for forestry reclamation than spruce or pine. The study also emphasizes the great value of spontaneous succession areas as full-fledged alternatives to forestry reclamation.

Spontaneous vegetation succession and recovery of ecosystem structure and function in a 40-year abandoned stone quarry in a Mexican tropical dryland

Background: The restoration of sites degraded by stone quarrying in drylands requires expensive interventions. However, these interventions cannot be used in tropical drylands because rural communities lack financial resources. Spontaneous vegetation succession may help restore degraded sites. However, spontaneous succession is evaluated by only comparing species composition between degraded and reference sites, without considering the structure and function of degraded sites. Question: Can spontaneous succession restore the structure and function of sites degraded by stone quarrying? Study sites and dates: San Rafael Coxcatlán, Puebla, 2013. Methods: We evaluated nine indicators of ecosystem structure and function in 4 degraded sites abandoned for 40 years and 1 reference site. Results: Spontaneous succession partially restored the structure and function of degraded sites. In all degraded sites, herb cover (20-49 %) and biocrust cover (21-51 %) were similar to those in reference site (19 %, 56 %). Three degraded sites also had canopy covers (57-76 %), shrub covers (51-52 %), and bare ground covers (2-3 %) similar to those in reference site (80 %, 42 %, 2 %). However, one degraded site displayed the opposite pattern (32 %, 8 %, 14 %). All degraded sites had lower tree cover (0-2 %), visual obstruction (6-25 %), and litter cover (3-30 %) than the reference site (21 %, 66 %, 77 %). Conclusions: Spontaneous succession helped restore the structure and function in some degraded sites.

Forest restoration after alluvial gold mining can recover vegetation structure. A case study in Colombia

Technical reclamation and spontaneous succession (passive restoration) are the two main approaches for restoring post-mining sites worldwide. Despite substantial differences between both approaches, little is known regarding how they differ in terms of ecological outcomes. We assessed and compared the vegetation structure and composition in one spontaneous succession forest that is 29 years old, two technically reclaimed forests that are 2 and 10 years old after alluvial gold mining, and one old-growth reference forest in northeastern Antioquia, Colombia. We sampled trees and saplings establishing three Modified-Whittaker Plots in each site. We measured tree basal area, canopy cover, vegetation height, tree density, and species richness. Vegetation structure and composition differed considerably among restoration approaches. Species richness was significantly greater in the spontaneous succession forest than at the other sites. Similarly, technical reclamation significantly increased the vegetation attributes after 10 years, reaching values similar to the reference forest. We underscore the importance of fast-growth planted species (Acacia mangium, Samanea saman, and Schizolobium parahyba) to revegetate mining degraded lands.

Mining sites: Landscape degradation or Opportunity for Biodiversity?

<p>Massive biodiversity loss, alarming the scientific community, is a hot topic nowadays. On the other hand, mining sites, active or closed, represent almost 1 percent of Earths’ surface. Mine safety imposes physical protection and isolation of mines by high fences, signs and guards in active and sometimes even in closed mines. Human activity, other than extraction, is most often legally restricted in mines, and hence the human disturbance is low; even in active mines, extraction is mostly taking place in one relatively small part of the mine, at one time, while the fence protects the whole mining area. As such, even active mines might present shelters for biodiversity, especially outside the working hours (late afternoon and night) for animal species, or in areas that are not exploited at the moment for plant species.</p><p>However, active and closed mines are rarely regarded as an opportunity for biodiversity. They are rather commonly regarded as degradations that require intense fixing actions. Instead of constantly rehabilitating them, in order to make them less dangerous for local populations or making them functional for humans – by giving them back the function they had before mining (i.e. agriculture, forestry) or creating a new one like landfill or industrial zone in quarries or fishing, hiking or other leisure activities in gravel pits – should we keep them protected and look at them as potential biodiversity reservoirs, in nowadays landscapes, overpopulated and generally highly impacted by human activities?</p><p>Should we rehabilitate mining sites or let them be biodiversity sanctuaries, where nature will develop itself as is suits her? Should we humans constantly try to “improve” and “help” nature, or should we let it be?</p><p>Existing studies showed that spontaneous succession can lead to valuable high-diversity habitats, but the attention given to its effect in mining sites has not yet been extensive. We studied biodiversity in mining sties, and we present empirical evidence suggesting that mining sites where nature has been left to develop on its own should be regarded as opportunities for biodiversity.</p><p>We compared the influence of four different rehabilitation techniques - mineral base left to spontaneous succession, mineral base covered with topsoil, mineral base covered with topsoil and planted, and mineral base covered with topsoil, sown and planted - on biodiversity development in quarries and gravel pits, in order to determine the technique that favors the most biodiversity development. We conducted inventories of five taxonomic groups present on-site after application of those four different rehabilitation techniques. 29 flora plots and 18 fauna transects were thoroughly inventoried, several times, in sites in northeastern France. We recorded 186 species of plants, 14 individuals/2 species of reptiles, 479/11 of amphibians, 91/39 of butterflies and 325/27 of dragonflies. For all five taxonomic groups, natural succession had the most favorable impact, compared to other rehabilitation techniques.</p><p>Our results suggest a necessity for a perspective change in favor of regarding mining sites as opportunities for becoming biodiversity shelters.</p>

Changes in Functional Response of Soil Microbial Community along Chronosequence of Spontaneous Succession on Post Mining Forest Sites Evaluated by Biolog and SIR Methods

Soil formation in post-mining sites is crucial for restoring ecosystem function, and soil formation depend on the accumulation of soil organic matter and the development of an active microbial community. In this study, we used substrate-induced respiration (SIR) and Biolog plates to characterize microbial catabolic profiles in a chronosequence of soil samples from 15 unreclaimed post-mining sites in Sokolov, Czech Republic. The sites had been undergoing spontaneous succession for 3 to 45 years. Biolog ECO plates included 31 substrates. Of substrates used for SIR (glucose, chitin, cellulose, Tween 80, phenylethylamine, N-acetyl-D-glucosamine, L-asparagine, D-mannitol, D-galacturonic acid, α-cyclodextrin, and 4-hydroxy benzoic acid), eight were also used for the Biolog plates. Soil respiration, total bacteria number, and culturable bacteria number were also measured. The total and culturable number of bacteria increased with site age (p < 0.01 and p < 0.05, respectively). The percentage of culturable bacteria decreased with site age (p < 0.01). Biolog analysis indicated that average well-color development (AWCD), evenness, and richness increased with site age. SIR data indicated that only average activities tended to increase with site age (p = 0.06). According to redundancy analysis (RDA), the eight substrates, which were commonly used in both methods (SIR and BIOLOG) explained 74.4% of the variation of data from all Biolog substrates. Among the eight substrates common to both methods, only data for N-acetyl-D-glucosamine were positively correlated (p < 0.01) between Biolog and SIR. Both methods revealed microbial catabolic profile changed along the chronosequence. PCA indicated that site age, soil carbon, and pH were the most important drivers of microbial catabolic profiles.

Effect of thermal activity on the differentiation of the vegetation of the “Ruda” postmining heap in Zabrze (Poland)

This paper presents the results of a study on the vegetation of the thermally active postmining heap “Ruda” in Zabrze (Poland). The aims of the study were: (i) to show the differentiation of the vegetation that has developed as a result of the thermal activity, and (ii) to determine the effect of thermal activity of the spoil heap on species richness and species diversity of the vegetation. Twelve plant communities were recorded on the heap. Thermal activity has a statistically significant impact on species richness (<em>Z</em> = 2.13, <em>p</em> = 0.03) and species diversity (<em>Z</em> = 2.29, <em>p</em> = 0.02). The species composition of plant communities reflects the habitat conditions, which are conditioned by thermal activity. As the distance from a zone with increased thermal activity increases, the degree of the spontaneous succession of vegetation and the complexity of the vegetation increase. Moreover, the share of annual species and kenophytes decreases in favor of perennial plants and apophytes. The number of plant communities (from four to eight), their species richness (number of species from 15 to 22) and species diversity (Shannon–Wiener diversity index from 1.81 to 2.19) also increase. A DCA analysis showed an increase in the shading, humidity and pH of the substrate, and the thickness of the dead organic matter within the gradient of the thermal activity.

Effects of Vegetation Pattern and Spontaneous Succession on Remediation of Potential Toxic Metal-Polluted Soil in Mine Dumps

The ecological rehabilitation of potential toxic metal-contaminated soils in sites disturbed by mining has been a great challenge in recent decades. Phytoremediation is one of the most widely promoted renovation methods due to its environmental friendliness and low cost. However, there is a lack of in situ investigation on the influence of vegetation pattern and spontaneous succession on the rehabilitation of potential toxic metal-polluted soil. To clarify how the vegetation pattern in the early stage of restoration and the spontaneous succession influence the remediation of the soil, we investigated a metal mining dump in Sichuan, China, by field investigation and laboratory analysis. We determined the plant growth, soil fertility, and the capacity of potential toxic metals (PTMs) in metal mining soil under different initial vegetation patterns for different years to understand the role of vegetation pattern and spontaneous succession in PTM pollution phytoremediation projects. The results show that: (1) Phytoremediation with a simple initial vegetation pattern (RP rehabilitative plant pattern) which involves two rehabilitation plants, Agave sisalana and Neyraudia reynaudiana, achieves a PTM pollution index that is 9.28% lower than that obtained with the complex vegetation pattern (RP&LP rehabilitation plants mixed with local plants pattern), 21.86% lower in the soil fertility index, and 73.69% lower in the biodiversity index; (2) The phytoremediation with the 10-year RP&LP pattern was associated with a PTM pollution index that was 4.04% higher than that for the 17-year RP&LP pattern, a soil fertility index that was 4.48% lower, and a biodiversity index that was 12.49% lower. During the process of vegetation succession, if accumulator plants face inhibition of growth or retreat, the reclamation rate will decrease. The vegetation patterns influence the effect of phytoremediation. Spontaneous vegetation succession will cause the phytoremediation process to deviate from the intended target. Therefore, according to the goal of vegetation restoration, choosing a suitable vegetation pattern is the main premise to ensure the effect of phytoremediation. The indispensable manipulation of succession is significant during the succession series, and more attention should be paid to the rehabilitative plants to ensure the stable effect of reclamation. The results obtained in this study could provide a guideline for the in situ remediation of PTM-polluted soil in China.