Woody Plant Diversity influences the Purification Efficiency of Simulated Vertical Flow Constructed Wetlands

Abstract In this study, an experimental system was conducted with 44 microcosms simulating vertical constructed wetlands (CWs), to explore the effect of woody plant species diversity on the purification efficiencies of CWs, and provide a scientific basis for assembling plant communities in CWs. Four woody species, Ligustrum obtusifolium, Hibiscus mutabilis, Hibiscus syriacus and Nerium oleander, were selected to set up species richness levels (1, 2, 4 species) and 11species compositions. The results showed that, the removal efficiency of TN, NH4+-N, TP and TOC in the CWs improved, with woody plant species richness increasing. The microcosms with four-species mixture had significantly higher removal rates of TN, NH4+-N, TP, and TOC, compared with the microcosms with monocultures. The woody plant species compositions had also impact on the pollutant removal capability of microcosms. The mixture of L. obtusifolium × H. mutabilis × H. syriacus × N. oleander exhibited the best purification effect for TN and NH4+-N, while the monoculture of N. oleander performed best for TP and TOC removal. The presence of N. oleander had a significant positive effect on the removal of pollutants in CWs.