Revegetation Enriched Microbial Carbon-, Nitrogen- and Phosphorus-Cycling Genes in Pb-Zn Tailings, Promoted Their Coupling, and Was Regulated by Plant Type and Colonization Time

Revegetation is recognized as one of the most effective strategies for the ecological restoration of tailings ponds. However, a systematic understanding of how both plant colonization time and plant type shape the microbial functional potential for coupled biogeochemical cycles remains insufficient. Here, we collected 24 samples comprising bare tailings and rhizosphere tailings from four dominant plant species (Miscanthus sinensis, Pinus massoniana, Lespedeza bicolor, Patrinia villosa) colonizing a lead–zinc mine tailings pond to investigate the effects of revegetation on the contents of carbon (C), nitrogen (N) and phosphorus (P) and microbial functional genes related to their cycles. The results showed that revegetation significantly increased the C, N and P contents in the rhizosphere tailings (p < 0.05), and these increased with plant colonization time. Compared with the bare tailings, the contents of C, N and P increased by 1.10 to 4.12 times, 1.06 to 4.84 times and 0.63 to 7.30 times, respectively. Furthermore, revegetation significantly enriches microbial C-, N- and P-cycling genes. The abundance of C fixation, organic degradation, nitrate reduction and organic P mineralization genes in tailings significantly increased after revegetation. Additionally, revegetation substantially enhanced the density, links and average degree of the network of microbial C-, N- and P-cycling genes. Pathway analysis using partial least squares path modeling indicated that revegetation positively affected microbial C-, N- and P-cycling genes, which were regulated by plant type and colonization time. Collectively, these findings suggest that revegetation can substantially enhance the biogeochemical cycling functions of microorganisms in tailings while also promoting their coupling.