Physiological and biochemical characteristics of biocrust in closed opencast coal mining areas: A study in Inner Mongolia, China

The biocrust is crucial in controlling erosion in arid and semi-arid regions, particularly in closed opencast coal mining areas. However, there is a lack of research concerning biocrust's physiological and biochemical characteristics in these mining environments and their relationship with various environmental factors. This gap in knowledge hinders the practical application of biocrusts for soil erosion control. Consequently, this study employed fluorescent quantitative PCR and high-throughput sequencing to examine the bacterial abundance and community diversity of biocrusts in the closed opencast mine in Zhalainuoer, Inner Mongolia, China. The results indicated that biocrusts significantly enriched soil nutrients. The upper layer of the biocrust exhibited a marked increase in available nutrients and organic matter content compared to bare soil, while the lower layer showed elevated levels of available nutrients, total phosphorus, and organic matter content. The physiological properties of moss within the biocrust were critically influenced by coverage, with chlorophyll a and soluble protein content increasing alongside coverage, whereas malondialdehyde content decreased as coverage declined. Bacterial diversity, as measured by the Chao1 and Shannon indices, significantly increased in both layers of the biocrust compared to bare soil. The dominant bacterial groups in the biocrust layers primarily included Proteobacteria, Actinobacteria, and Bacteroidetes at the phylum level. At the genus level, the predominant groups comprised Pseudarthrobacter, Sphingomonas, and Nocardioides. Among environmental factors, available phosphorus exerted the strongest influence on bacterial community composition, while total nitrogen had the weakest effect. Biocrusts modify bacterial communities to effectively manage nutrient cycling, enhancing the presence of key functional groups such as Actinobacteriota for carbon fixation, Nocardioides for nitrogen mineralization, and Acidobacteriota for phosphorus solubilization. The findings of this study provide practical references for evaluating the physical and chemical properties and bacterial communities of biocrusts in mining areas, thereby offering a mechanistic framework for employing biocrusts in sustainable mine rehabilitation.