Characters of soil algae during primary succession on copper mine dumps

PURPOSE: Algae play an important role in degraded areas during the initial stages of soil formation by improving its physico-chemical properties, reducing the erosion of soil, and thus favoring the settlement of vascular plants. This study investigates the characters of soil algal communities on copper tailing dumps and discusses the contribution of soil algae to the primary succession progress of young mine tailings ecosystems. MATERIALS AND METHODS: Five representative potential successional series (bare land, algae crust, mixed algal–moss crust, moss crust, and vegetated site) on copper tailing dumps and a nearby reference site were selected. The soil algae were identified using growth slide method, dilution plate method, and by direct microscopic observation of the soil suspensions. All experiments were carried in an incubation chamber at a temperature of 25 °C and with a 16 h/8 h light–dark cycle at a light intensity of 3,000 lux. RESULTS AND DISCUSSION: A total of 120 algal species were recorded. Cyanophyta (blue-green algae) were the most diverse taxonomic group, followed by Bacillariophyta (diatoms) and Chlorophyta (green algae), although diatoms were absolutely absent in bare sites. Diversity of soil algae was highest in vegetated site, whereas it was lowest in bare sites. Total algal abundance ranged between 0.15 × 10³ cells/g to 46.8 × 10³ cells/g dry soil, with the lowest abundance in the youngest site and the highest abundance in the mixed algal–moss crust site. Correlation analysis showed that the growth of soil algae was inhibited by high Cu, Zn, and Fe concentrations and low nutrient content and that the green algae were more sensitive to nutrient content than blue-green algae. CONCLUSIONS: Our results suggest that blue-green algae were most diverse, followed by diatoms and green algae. Species and abundance of soil algae in the tailings increased with the early succession process because of the decrease in heavy metal content and the improvement of nutrient conditions. The growth of soil algae created conditions for the settlement and growth of higher plants, but the appearance of moss and vascular plants inhibited the growth of soil algae.