A feasible method of induced biological soil crust propagation through the inoculation of moss and addition of soil amendments in a Pb-Zn tailing pond

Differences in Carbon and Nitrogen Cycling Strategies and Regional Variability in Biological Soil Crust Types

Biological soil crusts (BSCs) play a pivotal role in maintaining ecosystem stability and soil fertility in arid and semi-arid regions. However, the biogeographical differences in soil functional composition between cyanobacterial BSCs (C-BSCs) and moss BSCs (M-BSCs), particularly how environmental changes affect nutrient cycling strategies and microbial community functions, remain poorly understood. In this study, we investigated BSCs across aridity gradients (semi-humid, semi-arid, and arid regions) in China, focusing on carbon and nitrogen cycling pathways, enzyme activities, and nutrient acquisition strategies. It was found that aridity and BSC type had significant effects on the functional characteristics of microorganisms. This was demonstrated by significant differences in various soil microbial activities including enzyme activities and carbon and nitrogen nutrient cycling. With increasing aridity, C-BSCs exhibited reduced carbon cycling activity but enhanced nitrogen cycling processes, whereas M-BSCs displayed diminished activity in both carbon and nitrogen cycling. These divergent strategies were linked to soil properties such as pH and organic carbon content, with C-BSCs adapting through nitrogen-related processes (e.g., nifH, amoA) and M-BSCs relying on C fixation and degradation. These findings provide novel insights into the functional gene diversity of BSCs across different regions, offering valuable references for ecological restoration in arid areas. Specifically, our study highlights the potential of BSC inoculation for carbon and nitrogen enrichment in arid regions, with implications for climate-resilient restoration practices.

The adaptability, distribution, ecological function and restoration application of biological soil crusts on metal tailings: A critical review

A large amount of metal tailings causes many environmental issues. Thus, the techniques for their ecological restoration have garnered extensive attention. However, they are still in the exploratory stage. Biological soil crusts (BSCs) are a coherent layer comprising photoautotrophic organisms, heterotrophic organisms and soil particles. They are crucial in global terrestrial ecosystems and play an equal importance in metal tailings. We summarized the existing knowledge on BSCs growing on metal tailings. The main photosynthetic organisms (cyanobacteria, eukaryotic algae, lichens, and mosses) of BSCs exhibit a high heavy metal(loid) (HM) tolerance. BSCs also have a strong adaptability to other adverse conditions in tailings, such as poor structure, acidification, and infertility. The literature about tailing BSCs has been rapidly increasing, particularly after 2022. The extensive literature confirms that the BSCs distributed on metal tailings, including all major types of metal tailings in different climatic regisions, are common. BSCs perform various ecological functions in tailings, including HM stress reduction, soil structure improvement, soil nutrient increase, biogeochemical cycle enhancement, and microbial community restoration. They interact and accelerate revegetation of tailings (at least in the temperate zone) and soil formation. Restoring tailings by accelerating/inducing BSC formation (e.g., resource augmentation and inoculation) has also attracted attention and achieved small-scale on-site application. However, some knowledge gaps still exist. The potential areas for further research include the relation between BSCs and HMs, large-scale quantification of tailing BSCs, application of emerging biological techniques, controlled laboratory experiments, and other restoration applications.