Insights into the nurse effect of a native plant Ficus tikoua on Pb‒Zn tailing wastelands in western Hunan, China.

Abstract

Lead‒zinc (Pb‒Zn) processing and extraction activity generates large volumes of highly toxic and bare tailing (BT) wastelands which poses a potentially extreme risk to the surrounding environment. Revegetation in the Pb‒Zn tailing wastelands is usually considered a beneficial approach. Ficus tikoua is a native vine which can successfully colonize on Maoping Pb‒Zn mine tailing wastelands in western Hunan, China. This study involved examination of the nurse effect of F. tikoua on Pb‒Zn tailing wastelands, to provide insights into the potential mechanism of F. tikoua influencing soil quality and vegetation succession. The vegetation characteristics, nutrient properties, and heavy metal contents of three different types of vegetation patches associated with F. tikoua in Pb‒Zn tailing wastelands, representing different stage of succession, were investigated. The height, coverage, and aboveground and underground biomass of these vegetation patches showed an increasing trend from vegetation patch I (VP-I) to patch III (VP-III). The nutrient pool and chemical properties of these tailing wastelands gradually re-established from BT wasteland to VP-III. From VP-I to VP-III, the total heavy metal contents (i.e., Pb, Zn, Cu, and Cd) and DTPA-extractable Pb, Cu, and Cd contents significantly decreased, while the DTPA-extractable Zn content remained unchanged. Our findings suggested that F. tikoua exerts a distinct nurse plant effect by increasing the essential nutrient content of soil, reducing the available heavy metal content, and subsequently increasing the number of plant species and the biomass. Therefore, F. tikoua may be used as a promising nurse plant for triggering revegetation and phytostabilization of Pb‒Zn tailing wastelands at the initial stage of remediation.