Ecological Effects of Species Diversity on Plant Growth and Physico-Chemical Properties in a Pb-Zn Mine Tailings

Abstract

The remediation of metalliferous mine tailings remains a challenge in many regions of the world. A field experiment was conducted on representative Pb-Zn mine tailings with different species richness (1-, 4-, 8-, and 16-species) to evaluate the potential roles of species diversity in the phytoremediation of metalliferous mine tailings. The main results were ① high species diversity greatly enhanced vegetation cover and biomass. For example, the average vegetation cover and biomass were 33.4% and 66.7 g ·m-2 in 1-species plots and reached 78.4% and 183.8 g ·m-2 in 16-species plots, respectively. ② Plant species diversity had significant effects on nutrient accumulation. Total organic carbon (TOC), water organic carbon (SOC), total nitrogen (TN) and total phosphorus (TP) significantly increased with the species diversity (TOC:r=0.30,P<0.001; SOC:r=0.20,P<0.05; TN:r=0.24,P<0.05; TP:r=0.20,P<0.05). ③ Species diversity not only reduced the concentration of diethylenetriamine pentaacetate (DTPA)-extracted metals in the mine tailings, but also decreased heavy metal transfer and accumulation in the soil-plant system. With enhanced species diversity, DTPA-extracted Cd, Cu, Pb, and Zn decreased significantly (DTPA-Cd:r=0.20,P<0.05; DTPA-Cu:r=0.19, P<0.05; DTPA-Pb:r=0.23, P<0.05; DTPA-Zn:r=0.23, P<0.05). With increasing species diversity, a slightly decreasing trend was observed for Cd, Cu, Pb, and Zn concentrations in the aboveground parts of plants (Cd:r=-0.16, P<0.01; Cu:r=-0.23, P<0.001; Pb:r=-0.15, P<0.05; Zn:r=-0.18, P<0.001). In conclusion, plant diversity can play an important role in mine reclamation.