The effects of soil micro-environment on the adaptation of Cynodon dactylon (L.) Persoon in a copper smelter's slag dump.

Background and aims: Cynodon dactylon (L.) Persoon is a clonal plant often used in slope restoration and greening projects. Two different types of C. dactylon were found in a copper smelter's slag dump. The relationship between the two C. dactylon phenotypes and the micro-environment in the slag was investigated, aiming to identify the most suitable form of C. dactylon for restoring such slag dumps.

Methods: Copper, lead and zinc were extracted using the modified European Community Bureau of Reference sequential extraction procedure, and their morphologies were analysed. A risk screening procedure was used to assess the risk posed by soil contamination with Cu, Pb and Zn. Correlation analysis, redundancy analysis, principal component analysis and significance of difference were used to analyse the relationships between plant growth and the physicochemical properties of the soil and its Cu, Pb and Zn content. The structure of the microbial community was analysed using high-throughput sequencing.

Key results: With only mild Cu contamination, the Cu enrichment coefficient of upright C. dactylon (type B) reached 0.71. The Cu transport mode was rhizomatous. The Cu content of the roots was significantly higher (P ≤ 0.05) than that in creeping C. dactylon (type A), and the relative abundance of the rhizosphere microbial community was significantly greater (P ≤ 0.01) than that of the A-type. The function of the genes is mainly metabolic, followed by replication and repair functions.

Conclusions: Upright C. dactylon (B) exhibits a capacity for Cu enrichment that makes it highly promising for the ecological restoration of copper smelting slag dumps.