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Road-based transport emissions are a major source of atmospheric metal pollution. However, there have been few studies on emissions from road traffic in mountainous areas. In this study, epiphytic mosses from trees at different elevations of a highway, a typical road with extraordinary elevation change in a mountainous area of karst in Guizhou, China, were analyzed for metal content as well as the spatial distribution pattern of metals. Mosses were sampled from three sections of highway at different elevations, from 1292-1357, 1394-1441, to 1481-1548 m. Principal component analysis and heat-map clustering were used to identify the principal factors affecting metal deposition. The results show that the metals of mosses from different elevations were divided into four factors. Group 1 which included Ni, Fe, Mg, Ba, and Al was attributed to a dominantly geogenic source. Group 2 included Zn, Cu, Mn, and Cr, from vehicle-related materials including tires and brakes. Group 3, Cd, can be attributed to high Cd background levels from local origins and traffic emissions, particularly tire wear. Group 4, Pb, is associated with brake wear and historical deposition. The epiphytic moss widely distributed in the study area, Ectropothecium aneitense Broth. & Watts, was used to analyze the spatial distribution pattern of the metals. Metal content gradually decreased with increase in elevation. Levels of Ni, Fe, Mn, Ba, and Cd were all significantly correlated with elevation (p < 0.05), simultaneously affected by terrain and vertically stratified. We highlighted the vertical distribution characteristics of metal in epiphytic mosses in this study, which could improve moss application for ecological monitoring due to road-based transport emissions with elevation changes.

The diversity of bryophytes in karst sinkholes has received little attention, and these habitats probably play a crucial role as refugia. In this study, bryophyte diversity affected by different levels of human disturbance in five karst sinkholes was compared. A total of 132 species of bryophytes (17 liverworts and 115 mosses) that belong to 64 genera and 30 families were recorded. The richness of the bryophytes in the natural sinkholes was significantly higher than that of the bryophytes in the sinkholes affected by tourism and used as farmland. Canonical correspondence analysis showed that soil moisture is one of the most important factors that affect the abundance of bryophyte distribution in the five sinkholes. Human activities, including agriculture, animal husbandry, and tourism development, reduce the bryophyte coverage of sinkholes and lead to soil moisture loss. Therefore, effective protection of karst sinkholes is required to maintain their original value for biodiversity conservation.

Heavy metal pollution caused by the development and utilization of Karst caves seriously threatens the cave environment and groundwater. Understanding the pollution dynamics has important practical significance for monitoring the cave environment. Here, the characteristics and heavy metals of the bryophytes in a typical Dark River Cave, Zhijin Cave, in Guizhou province were studied to explore the effect of the bryophyte community on cave pollution. A total of 34 types of bryophyte communities were observed, representing 49 taxa of bryophytes (12 of liverworts, 37 of mosses) in 33 genera (8 of liverworts, 25 of mosses) and 20 families (8 of liverworts, 12 of mosses). The dominant families were Pottiaceae, Fissidentaceae and Mniaceae, comprising 16%, 14%, and 14% of all taxa, respectively. Mercury (Hg) levels were up to 59.45, much higher than Cr and Zn, which indicates that Hg is the most serious pollutant in caves. The bryophyte community index showed a decreasing trend with an increase in heavy metal pollution. The Hg content of the measured heavy metals was significantly negatively correlated with its corresponding bryophyte community indices (P < 0.05), which indicates that the bryophyte community characteristics can accurately reflect the level of Hg pollution within a cave. The RDA sequencing results showed that bryophyte •研究报告• © 1278 生 物 多 样 性 Biodiversity Science 第 26 卷 研究报告 communities in Karst caves adapt to low photometric environment and thus exhibit photopic movement, grow well in Ca substrate and are resistant to heavy metals. The Hg content in the Conocephalum conicum was significantly correlated with its substrate Hg content (P < 0.05). This shows that C. conicum is affected by the substrate Hg pollution. In the future, C. conicum can be used as one of the biomonitoring materials for cave environments.

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Mining activities have been shown to affect the rate of carbon decomposition in aquatic ecosystems by altering the traits of the organic matter (e.g., leaf litter). However, the ecological function of soil microbes that enter aquatic ecosystems in association with organic matter is not known. Here, standardized cotton strip assays (CSA) were used to quantify the effects of soil microbial colonization location (mine vs. forest riverbank) and time (7 days vs. 14 days) on cellulose decomposition in aquatic ecosystems. The CSA results showed that the mine riverbank location and microbial colonization time had significant effects on the microbial community structure, microbial biomass, and functional genes of cellulose decomposition. Compared with the forest riparian zone, the fungal biomass and bacterial cellulose‐decomposing gene (GH48) abundance of cotton strips colonized in the mine riparian zone for 14 days were 12.5‐times and 54.93‐times higher than that of the cotton strips colonized in the forest riparian zone, respectively, while the fungal cellulose‐decomposing gene (cbhI) was detected only after 14 days of colonization. After 90 days of stream incubation, the decomposition rate and GH48 gene abundance of cotton strips colonized in the mine riparian zone for 14 days were significantly higher than those of cotton strips colonized in the forest riparian zone. However, the abundance of the cbhI gene in cotton strips colonized for 14 days was significantly higher than that in cotton strips colonized for 7 days. These results show that bacteria were mainly affected by the microbial colonization environment, while fungi were mainly affected by colonization time. Mining activities accelerate the decomposition of organic matter in aquatic ecosystems by increasing soil fungal biomass and bacterial cellulose decomposition genes. To reduce the carbon loss of aquatic ecosystems, it is necessary to study the potential influence of soil microbes on the decomposition of organic carbon in riparian zones.

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