Corticolous lichens as environmental indicators of natural sulphur emissions near the sulphur mine El Vinagre (Cauca, Colombia)

摘要

The aim of this study was to evaluate the spatial effect of a natural source of sulphur pollution on the species diversity, richness and distribution of corticolous lichens in a paramo zone at the mine 'El Vinagre' (Purace, Cauca, Colombia). Three zones at different distances from the pollution source were established: zone 1 with a high degree of contamination, a potentially mildly affected or transitional zone 2, and a zone 3 free of disturbance. In each zone, 10 phorophytes of Weinmannia microphylla (Cunoniaceae) were sampled, and all lichens in a 150 cm vertical transect 50 cm above the ground were collected and identified. Phorophyte parameters were measured (bark pH and diameter at breast height) and the samples were georeferenced. In order to evaluate the impact on lichens, non-metric multidimensional scaling (NMS) and indicator species analysis were carried out. ANOVA and Spearman correlations were performed to assess the relationships of environmental and tree variables between zones and with lichen community structure. The index of atmospheric purity (IAP) and the environmental rating factor (FCA) were evaluated for the three zones. In total, 104 lichen species were recorded, of which 72 were identified to species, 17 to genus, and four to family; 11 samples could not be identified. NMS clustered samples according to zone and the main axis which were correlated with bark pH and distance from pollution source. We found eight indicator species characterizing different zones, and four marginally significant indicator species. Using the IAP, we established three isocontamination areas, with zones 2 and 3 classified as more or less pristine zones and zone 1 as a polluted zone (supported by bark pH as a proxy for current pollution). Diversity was lowest in zone 1, closest to the pollution source, and lichen species composition differed between zones. Differences between lichens in zones 2 and 3 appear mostly unrelated to the current pollution source and might be more related to historical differences in impact from a 20-year-old pollution source.