Abstract
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 5588.00 μg/g and 4283.41 μg/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.
Highlights
Guizhou province, located in southwest China, has high levels of metallic minerals in its soil. e manganese reserves in Guizhou province account for about 60% of the national manganese reserves and mainly concentrate in Tongren city [1]
We found that bryophytes crust exists in all the places where vascular plants grow in the manganese solid wastes areas. is phenomenon prompts us to realize the following questions: (1) What was the biodiversity of bryophytes and dominant species in manganese solid wastes areas? (2) What characteristics do bryophytes have for heavy metal accumulation? (3) What were the effects of bryophytes on the growth substrate and the symbiotic bacterial community structure? (4) How was microbial community structure related to soil factors influenced by bryophytes?
Samples were collected in July 2020. e study involved two different types of manganese solid wastes areas: mine waste slag areas (A, site in Yinjiang county), which is composed of waste rocks and a small amount of tailings produced during manganese mining; electrolytic manganese slag areas (B, site in Songtao county), which is a kind of solid wastes with high moisture contents
Summary
Guizhou province, located in southwest China, has high levels of metallic minerals in its soil. e manganese reserves in Guizhou province account for about 60% of the national manganese reserves and mainly concentrate in Tongren city [1]. In 2014, the production of electrolytic manganese slag was about millions of tons in Tongren city [5], and the heavy metal pollution in mining areas has attracted the attention of many scholars. Bryophytes, the most primitive higher plants with strong water holding capacity, are effective accumulators of elements and play an important role in restoring soil fertility [9,10,11]. E research about bryophytes and symbiotic bacteria mainly concentrated on deserts, forests, grasslands, and degraded karst areas [26,27,28,29]. Ese studies are numerous, but studies on the accumulation of heavy metals in bryophytes in manganese solid wastes areas and their effects on growth substrate are lacking. We found that bryophytes crust exists in all the places where vascular plants grow in the manganese solid wastes areas. E findings from this study should provide a theoretical basis for bryophytes to be the typical stress-resistant plants and the pioneers of ecosystem reconstruction in mining areas
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