Effects of heavy metals on moss diversity and analysis of moss indicator species in Nancha manganese mining area, Southwestern China

Abstract

Understanding the spatial distribution pattern, species characteristics of moss taxa, and their relationship with heavy metals is important for biodiversity conservation and heavy metals pollution management in manganese mining areas. Characteristics of moss species in four functional areas, including, Mine entrance, Waste rock area, Transportation line, Manganese ore storage, were explored using abundance index, α diversity indices, and β diversity indices. Distance-based Redundancy Analysis was used to explore the relationship between changes in moss β-diversity and soil heavy metals. Multivariate-Regression-Trees were used to determine moss indicator species. A total of 22 species of mosses, comprising 14 genera from 7 families, were identified in the study area. The most dominant families were Bryaceae and Pottiaceae. Soil heavy metals were significantly affected species diversity, species replacement (R2adj = 0.495, P = 0.001), and species richness (R2adj = 0.667, P = 0.001). In functional areas with low levels of heavy metals, moss species diversity was high, probability of species replacement was low, and variation in species richness was low. On the contrary, in functional areas with high heavy metal content, moss species diversity was low, probability of species replacement was high, and variation of species richness was high. The classification results of the sampling plots showed presence of six indicator species (Brachymeniopsis gymnostoma, Funaria attenuata, Trichostomum brachydontium, Encalypta ciliata, Molendoa sendtneriana, and Plagiobryum zieri) in the Mine entrance whereas no indicator species were observed in the Transport line. In addition, only one indicator species (Barbula subcontorta) was observed in the Waste rock area, and five indicator species (Bryum blindii, Physcomitrium repandum, Philonotis secunda, Brachymenium exile, and Syrrhopodon prolifer) were present in the Manganese ore storage. These findings show that more indicator species occur in areas with relatively high or low heavy metals content, whereas fewer indicator species occur in areas with relatively moderate-heavy metals content.