Biocrusts Forming Cyanobacteria Favor Plant Germination and Improve the Quality of Soil Mixed with Tailings Sands

摘要

Revegetation is a necessary step for the rehabilitation of soils impacted by mining activities, and requires an adequate amount of nutrients. Biocrusts (BSC) are biotic communities formed after the degraded site has been colonized by cyanobacteria, which supplement nutrients and favor the germination of some plant species.Cultures of BSC-forming cyanobacteria previously identified and isolated from different geographical zones of Chile, were used to evaluate the effect of the microbial cultures on the germination and growth of Polypogon australis plants. The cyanobacteria cultures were inoculated on substrates composed by a mix of soil and copper mine-tailing sands. The establishment of the cyanobacteria on the soil mixes was observed by optical and confocal microscopy. The germination index, and the roots and leaves growth of the plant species were determined. Physicochemical parameters of the soil mix were determined before and after the cyanobacterial inoculation. The results showed that the cumulative germination of the plant species was significantly higher in the presence of the cyanobacteria than in the controls with bacterial culture media or water. A similar result was observed for the growth of P. australis in the presence of cyanobacteria, showing a stimulating effect on the leaves length of the plants respect to the controls. The organic matter content (OM) increased after the inoculation of the soil mix with the cyanobacterial culture, and the electrical conductivity (EC) was alleviated due to the cyanobacterial inoculation. We propose that BSC-forming cyanobacteria inoculation can be used as a first step for a successful revegetation of mining sites. The inoculation of mining polluted soil with BSC-forming cyanobacteria diminishes the phytotoxicity of the substrates and may favor the establishment of plant species.