Ecological Restoration Of Mining Areas Research Articles

Reclamation patterns vary carbon sequestration by trees and soils in an opencast coal mine, China

Reforestation is often recommended for ecological restoration in mining areas because of tree's high stand-level productivity and satisfied carbon (C) and other nutrient sequestration objectives. However, the C sequestration efficiency of different plantation patterns or different tree species is rarely understood. In order to get insight of the C sequestration efficiency by trees and soils of different reclamation patterns in Pingshuo opencast coal mine, Shanxi Province, China, three different reclamation patterns (developed for 17years) at three permanent fixed plots, broadleaf mixed forest: R. pseudoacacia-U. pumila-A. altissima (Plot code: BM), broadleaf conifer mixed forest: R. pseudoacacia-P. tabulaeformis (Plot code: BC) and broadleaf monoculture forest: R. pseudoacacia (Plot code: BR), were selected and investigated. The results showed that tree volumes and biomass differed significantly after 17years' succession, from 21.58m3 and 36.02Mgha−1 of the broadleaf monoculture forest (BR) to 37.20m3 and 48.73Mgha−1 of broadleaf conifer mixed forest (BC). Accordingly, tree C and litter C were observed higher in BC (24.37 and 2.26Mgha−1) than BM (19.25 and 1.15Mgha−1) and BR (18.01 and 1.31Mgha−1). Herb C, however, was observed lower in BC (0.02Mgha−1) than BR (0.25Mgha−1) and BM (0.24Mgha−1). C sequestrated in soil organic matter varied in the order: BC (172.16Mgha−1)>BM (73.79Mgha−1)>BR (51.59Mgha−1) and the top layer (0-20cm) C contributed a large portion (varied from 37% in BC to 53% in BM) of the total soil C. Consequently, BC sequestrated the highest total C (198.81Mgha−1) by plant, litter and soil, followed by BM (94.43Mgha−1) and BR (71.16Mgha−1). In regard to the total C distribution, a major portion of the total C consisted of soil C (varied from 72.49% in BR to 86.60% in BC). Overall, this study indicated that mixed forest facilitated sequestrating more C than pure forest, and the broadleaf conifer mixed forest: R. pseudoacacia-P. tabulaeformis not only accumulated more plant biomass but also accelerated the soil C sequestration which may be suggested as the more suitable pattern for the opencast coal mine reclamation in the region of eastern Loess Plateau of China.

The Effects of Various Land Reclamation Scenarios on the Succession of Soil Bacteria, Archaea, and Fungi Over the Short and Long Term

Ecological restoration of mining areas has mainly focused on the succession dynamics of vegetation and the fate of microbial communities remains poorly understood. We examined changes in soil characteristics and plant and microbial communities with increasing reclamation period in an open coal mine. Bacterial, archaeal and fungal communities were assessed by tag-encoded 454 pyrosequencing. At the phylum level, Proteobacteria, Crenarchaeota, and Ascomycota had the highest detected relative abundance within bacteria, archaea, and fungi, respectively. Partial regressions and canonical correspondence analysis demonstrated that vegetation played a major role in bacterial and archaeal diversity and assemblies, and soil characteristics, especially nitrogen, were important for fungal diversity and assemblies. Spearman rank correlation indicated that bacterial and archaeal communities showed synergistic succession with plants; whereas, fungal communities showed no such pattern. Overall, our data suggest that there are different drivers of bacterial, archaeal and fungal succession during secondary succession in a reclaimed open mine.

Development of population structure and spatial distribution patterns of a restored forest during 17-year succession (1993-2010) in Pingshuo opencast mine spoil, China.

Afforestation of native tree species is often recommended for ecological restoration in mining areas, but the understanding of the ecological processes of restored vegetation is quite limited. In order to provide insight of the ecological processes of restored vegetation, in this study, we investigate the development of the population structure and spatial distribution patterns of restored Robinia pseudoacacia (ROPS) and Pinus tabuliformis (PITA) mixed forests during the 17years of the mine spoil period of the Pingshuo opencast mine, Shanxi Province, China. After a 17-year succession, apart from the two planted species, Ulmus pumila (ULPU), as an invasive species, settled in the plot along with a large number of small diameter at breast height (DBH) size. In total, there are 10,062 living individual plants, much more than that at the plantation (5105), and ROPS had become the dominant species with a section area with a breast height of 9.40m(2)hm(-2) and a mean DBH of 6.72cm, much higher than both PITA and ULPU. The DBH size classes of all the total species showed inverted J-shaped distributions, which may have been a result of the large number of small regenerated ULPU trees. The DBH size classes of both ROPS and PITA showed peak-type structures with individuals mainly gathering in the moderate DBH size class, indicating a relatively healthy DBH size class structure. Meanwhile, invasive ULPU were distributed in a clear L shape, concentrating on the small DBH size class, indicating a relatively low survival rate for adult trees. Both ROPS and PITA species survival in the plantation showed uniform and aggregated distribution at small scales and random with scales increasing. ULPU showed a strong aggregation at small scales as well as random with scales increasing. Both the population structure and spatial distribution indicated that ROPS dominates and will continue to dominate the community in the future succession, which should be continuously monitored.

A practical framework for scenario-based optimal decision-making on water-deficient river ecological restoration in mining areas

Mining activities may cause serious damages to the river ecological environment in mining areas. It has been realized that challenging is faced for optimal decision-making on the river ecological restoration resulting from system complexity, multi-objectives, long term restoration in which multiple stages may be needed to take, and difficulty in detailed process quantification. By analyzing and fully reflecting the differences between the central zone and surrounding zones of the restored river passing through the mining area, the comprehensive evaluation index systems of the central zone and surrounding zones are separately suggested firstly. Then a scenario-based optimization decision-making model for river ecological restoration in mining areas was established with taking advantages of spatial divisions and following procedure of first going through optimization by sub-region level, then optimizing by integration. Then, a framework for scenario-based optimal decision-making on water-deficient river ecological restoration in mining areas is proposed in which a multi-objective and multi-stage spatial division optimization method is considered to improve decision-making efficiency and enhance its practicability. It is indicated that this optimization framework is reasonable and practical, which is expected to offer reliable decision support in identifying the effective solutions on optimal management of the water-deficient river ecological restoration in mining areas. At the same time, it has implications in general land reclamation and ecological restoration in the mining areas.

Experimental investigation on rainfall infiltration and solute transport in layered porous and fractured media

Layered structures with upper porous and lower fractured media are widely distributed in the world. An experimental investigation on rainfall infiltration and solute transport in such layered structures can provide the necessary foundation for effectively preventing and forecasting water bursting in mines, controlling contamination of mine water, and accomplishing ecological restoration of mining areas. A typical physical model of the layered structures with porous and fractured media was created in this study. Then rainfall infiltration experiments were conducted after salt solution was sprayed on the surface of the layered structure. The volumetric water content and concentration of chlorine ions at different specified positions along the profile of the experiment system were measured in real-time. The experimental results showed that the lower fractured media, with a considerably higher permeability than that of the upper porous media, had significant effects on preventing water infiltration. Moreover, although the porous media were homogeneous statistically in the whole domain, spatial variations in the features of effluent concentrations with regards to time, or so called breakthrough curves, at various sampling points located at the horizontal plane in the porous media near the porous-fractured interface were observed, indicating the diversity of solute transport at small scales. Furthermore, the breakthrough curves of the outflow at the bottom, located beneath the underlying fractured rock, were able to capture and integrate features of the breakthrough curves of both the upper porous and fractured media, which exhibited multiple peaks, while the peak values were reduced one by one with time.