More than just a substrate for mites: Moss-dominated biological soil crust protected population of the oribatid mite, Oppia nitens against cadmium toxicity in soil

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.

Differences of oribatid mite community and trophic structure between karst caves and surface different moss habitats

In order to reveal the community characteristics and trophic structure of oribatid mites in different moss habitats in karst caves, the oribatid mites in the moss habitats of ground (GD), understory (US), cave wall (CW), surface shrub (SB) and farmland (FL) outside the cave were collected in October 2021. Through the identification and data analysis of oribatid mites, 2352 oribatid mites were found, belonging to 45 families and 72 genera, most of which were Gymnonota. The family number, genus number, individual number, individual density, dominant genus composition, community diversity, community similarity, MGP (Analysis methods for ecological groups of oribatid mites) ecological group of oribatid mites and trophic structure of oribatid mites in different moss were analyzed. The results showed that: (1) The number of families, genera, individuals, and individual density of SB and FL are higher than those of the other three habitats; (2) Platyliodes, Oppiella, Tectocepheus, Scutovertex, Scheloribates and Trichogalumna are the dominant genera of the oribatid mites in the cave moss habitat, among them, Tectocepheus and Trichogaluna have the most obvious advantages; (3) The diversity index of shrub (SB) was higher than that of other four habitats; Similarity between ground and cave wall, shrub and farmland is high; (4) The MGP ecological group of oribatid mites in different habitats is dominated by O type (Overall type belongs to MGP analysis results, 20%≤M,G,P≤50%), and a total of 42 genera of oribatid mites preliminarily constitute the trophic structure of oribatid mites in the cave moss habitat. Based on the above results, it can be concluded that there are differences in the community structure of oribatid mites in different moss habitats in the study area, and the use of dominant genera of mites can preliminarily indicate the environmental conditions of different moss habitats. This study enriches the study of mites in karst cave mosses, and can provide theoretical significance for the protection of cave biodiversity in karst areas.