The mining of manganese brings excellent wealth to humankind. However, it destroys the ecological environment, mainly manifested as heavy metal pollution and vegetation destruction. The restoration of ecological vegetation in manganese mining areas has become an important work after mineral exploitation. The effect of bryophytes on ecological restoration in mining areas is irreplaceable. The bryophytes diversity and its pioneering role in two types of manganese waste residue areas were investigated in Guizhou province, China. The results showed that there were 24 species of mosses in mine waste slag areas, and all of them belonged to 6 families and 15 genera; the species Gymnostomum subrigidulum, Pohlia gedeana, and Bryum atrovirens were the dominant mosses. There were 6 species of mosses in electrolytic manganese slag areas, and all of them belonged to 5 families and 5 genera. The dominant moss was B. atrovirens. The bryophytes diversity in the electrolytic manganese slag areas with lower pH was poorer than that in mine slag areas. The accumulation of heavy metals in mosses showed that B. atrovirens collected from two types of areas had a strong ability to accumulate Mn with the cumulants 5588.00μg/g and 4283.41μg/g, respectively. All mosses had a strong enrichment ability to Cd. It indicated that mosses had strong tolerance to heavy metals. Bryophytes increased the available nutrients and bacterial community diversity of mosses growth substrates in two types of areas. Besides, we studied the relationships between bacterial community structure and soil factors. The main soil factor affecting the bacterial community structure was available nitrogen (AN) in mine waste slag areas, while it was pH in the electrolytic manganese residue areas. The systematic study suggested that bryophytes increased the available nutrients and the microbial community diversity of the growth substrates in manganese waste residue areas, which provided the basic conditions for the growth of vascular plants.

In recent decades, China has exhibited the fastest and most remarkable social-economic development in the world. As a result of such development, the forest cover of the country has undergone radical changes. This paper aims to develop a method for analyzing long-term and spatial changes in forest cover based on historical maps and remote sensing images. Moreover, we will focus on the reduction or restoration of forests distributed at different altitudes, slopes, soils, and lithologic types in different periods, to reveal the problems that should be paid attention to in forest restoration in karst areas. A typical county of China was selected as the study area. A historical military operation map was considered the principal source of basic data. These data were then combined with Landsat satellite images to conduct quantitative analysis on changes in the spatial area and location of forest cover with a long time series. The findings are as follows: in terms of time series, the forest area in the study area showed a trend of decreasing at first and then increasing, with the year 1986 as the turning point. In terms of spatial patterns, a considerable difference is observed in regions with changes in forest cover under different historical periods. Changes are obvious in limestone areas, rock soil areas, and areas with an elevation of 2000–2500 m and a slope gradient of 6°–15°. Spatial–temporal changes in forest cover reflect the effects of the war, national policy, and economic development to some extent. All these results indicate that, despite its limitations, a historical map is a valuable document for studying an ecological environment.

The rhizospheres of three dominant plant species (Miscanthus floridulus, Buddleja lindleyana, and Erigeron annuus) growing in manganese residue disposal sites in eastern Guizhou Province, China, were analyzed to study the effects of plant growth on the nutrient levels and bacterial community structure of two types of manganese residues. The results showed that the growth of the three species improved the nutritional composition of manganese residues; the available nitrogen (AN) contents of the manganese mine residue significantly increased by 29.56–60.78% while the available phosphorus (AP) contents of the electrolytic manganese residue significantly increased by 30.24–44.41% compared to those in unvegetated manganese residue. The diversity of the bacterial community in the manganese mine residue increased significantly due to plant growth. Proteobacteria, Acidobacteria, and Bacteroidetes were the dominant phyla in both manganese residues. Sphingomonas and GP6 were the dominant bacterial genera. The relative abundance of the Firmicutes phylum was significantly higher in the manganese mine residue than in the control and that of the Thiobacillus genus was lower, which indicated improvements in the microenvironment. Correlation analysis showed that OM and AN were the main nutrient factors affecting the bacterial community structure in the manganese mine residue. Novelty statement At present, research on the phytoremediation of manganese residue disposal sites focuses mostly on the investigation of different plant types and their heavy metal accumulation and transformation characteristics. However, comparative studies of the differences in growth matrix characteristics between plant growth areas and exposed areas are lacking. In addition, dominant plant species are regionally distributed. The previous studies were mostly concentrated in Chongqing, Guangxi, and Hunan in China. The eastern region of Guizhou Province is located in the “Manganese Triangle” area of China, where the manganese resources account for about 50% of the national total. There is no report on the phytoremediation of manganese residue disposal sites in this region. Therefore, the rhizospheres of three dominant plant species (Miscanthus floridulus, Buddleja lindleyana, and Erigeron annuus) growing in manganese residue disposal sites in eastern Guizhou Province, China, were analyzed to study the effects of plant growth on the nutrient levels and bacterial community structure of two types of manganese residues (manganese mine residue and electrolytic manganese residue). This study could provide useful theoretical information to benefit the ecological restoration of manganese residue disposal sites.

This study investigates the growth dynamics and heavy metal immobilization in Sudan grass cultivated on substrates composed of electrolytic manganese residue (EMR), phosphogypsum, and chili straw biochar. Pot experiments revealed that a substrate with phosphogypsum constituting 75% of the mix hinders Sudan grass seed germination. Compared with sole EMR utilization, the composite substrates notably enhanced plant growth, evidenced by increases in plant height and fresh weight. The integration of these substrates led to a significant elevation in total chlorophyll content (up to 54.39%) and a reduction in malondialdehyde (MDA) levels (up to 21.66%), indicating improved photosynthetic activity and lower oxidative stress. The addition of biochar reduced the content of Zn, Cd, and Mn in the roots of Sudan grass by up to 25.92%, 20.00%, and 43.17%, respectively; and reduced the content of Pb, Mn, and Cr in the shoot by up to 33.72%, 17.53%, and 26.32%, respectively. Fuzzy membership function analysis identified the optimal substrate composition as 75% EMR and 25% phosphogypsum, with 5% chili straw biochar, based on overall performance metrics. This study adopts the concept of “to treat waste with waste”. The approach is to fully consider the fertility characteristics of EMR, phosphogypsum, and biochar, underscoring the potential for utilizing waste-derived materials in cultivating Sudan grass and offering a sustainable approach to plant growth and heavy metal management.