Abstract:The root and shoot growth, root biomass, and root distribution of four species, such as Cyperus flabelliformis, Hymenocallis littoralis, Phragmites australis, and Vetiveria zizanioides, were studied in a surface-flow constructed wetland. The results showed that root and shoot growth pattern were similar among C. flabelliformis, V. zizanioides, and H. littoralis, with a fast growth stage before September or October, and a slow growth stage during the following months, while P. australis was very different, with slow growth of root and shoot before July, and rapid growth maintained throughout winter. H. littoralis exhibited significantly faster root growth and significantly larger root biomass than other species (P<0.01), while V. zizanioides showed significantly slower root growth and a significantly smaller root biomass than other species (P<0.01). Roots of V. zizanioides generally grew vertically, while the roots of the other species were predominantly distributed in the shallow layer of the substrate. C. flabelliformis produced the most tillers, and had the highest leaf area index (LAI), while V. zizanioides showed the smallest LAI. The results suggest that P. australis could be planted with other wetland species to achieve high decontamination rates in treatment wetlands during the autumn and winter months. Results also suggest that H. littoralis, a lower stratum plant, could be paired with tall and early growing species like C. flabelliformis as a beneficial component of the poly-cultivated wetland community.
