Effects of Plant Diversity and Plant Density on Ecosystem Functions in Floating Constructed Wetlands

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Effects of Plant Diversity and Plant Density on Ecosystem Functions in Floating Constructed Wetlands Wenjuan Han & Xiaoling Sheng & Jiongni Shao & Jia Jiang & Qinru He & Ying Lin

Received: 6 July 2020 / Accepted: 26 October 2020 # Springer Nature Switzerland AG 2020

Abstract Plant species diversity could enhance plant productivity and pollutant removal efficiency in constructed wetlands (CWs). However, the potential importance of plant density for ecosystem functioning has largely been neglected. In this study, we conducted a factorial experiment in which three common plant species were planted in a gradient of species richness (one, two, and three) and seven species compositions at two densities (six and twelve individuals per microcosm). Plant total biomass and total organic carbon (TOC) and total inorganic nitrogen (TIN) removal efficiency were measured to explore the effect of plant species diversity and density on the ecosystem functioning of CWs. Results showed that (1) plant species richness had no significant effect on plant total biomass and TOC and TIN removal efficiency under high and low plant density. (2) There were significant differences in TIN removal efficiency among seven species compositions under low plant density; especially, the presence of Canna indica reduced the TIN removal efficiency. In contrast, species composition and species identity had Supplementary Information The online version contains supplementary material available at https://doi.org/10.1007 /s11270-020-04913-3. W. Han College of Life and Environmental Science, Wenzhou University, Wenzhou 325035 Zhejiang, China W. Han (*) : X. Sheng : J. Shao : J. Jiang : Q. He : Y. Lin College of Chemistry and Life Sciences, Zhejiang Normal University, Jinhua 321004 Zhejiang, China e-mail: [email protected]

no significant effect on ecosystem functioning under high plant density. (3) High plant density increased plant total biomass of C. indica monocultures, and also enhanced TIN removal efficiency in mixtures of two species. These results indicated C. indica alone may not be an ideal species for enhancing pollutant removal in constructed wetlands but planting at high density could mitigate its negative effect on ecosystem functioning. Keywords Species richness . Species composition . Species identity . Plant biomass . TOC removal efficiency . TIN removal efficiency

1 Introduction Rapid growth of urbanization and industrial development are often associated with substantial wastewater production that has become a serious problem affecting water quality and human health (Galloway et al. 2008; Gu et al. 2013). Excessive nitrogen (N) loading to aquatic ecosystems may contribute to nutrient enrichment or eutrophication (Conley et al. 2009; Chen et al. 2011). Untreated organic carbon often depletes dissolved oxygen in aquatic ecosystems, causing widespread mortality of aquatic organisms (Saeed and Sun 2012). The treatment of wastewater with high N and organic carbon loading remains a challenge around the world. As a green treatment technology, con