Both species richness and growth forms affect nutrient removal in constructed wetlands: A mesocosm experiment

Abstract

IntroductionPlant richness is thought to improve the function of constructed wetlands (CWs), but most CWs are planted with monocultures, with only a few employed polycultures, which have drawn contradictory conclusions. We suppose functional diversity is the key to better performance of plant communities and hypothesize that CWs planted with diverse growth forms are superior in plant growth and nutrient removal.MethodsIn this study, six emergent plant species categorized into slender type (Schoenoplectus tabernaemontani, Typha orientalis), fan type (Iris sibirica, Acorus calamus) and large type (Canna indica and Thalia dealbata) were planted in monocultures, combinations (two species of the same growth form) and mixed polycultures (six species of three growth forms). We then compared how plant growth and nutrient uptake differed among treatments.ResultsIt showed that the polyculture considerably increased the removal of total nitrogen (TN) and total phosphorus (TP), but the combination did not outperform monoculture. High consistency in the patterns between underground biomass and total biomass indicated that plant roots were essential for nutrient consumption. Compared with slender and fan plants, the large plants had a greater biomass increase in polycultures, which greatly accelerated the absorption and assimilation of TN and TP.ConclusionOur study indicated that plant community with various growth forms reduced the intensity of interspecific competition, increased the functional diversity, and greatly enhanced the ability of pollutant removal. Our results also provide some suggestions for plant selection and combination designs in CWs.

Engineering Aquatic Plant Community Composition on Floating Treatment Wetlands Can Increase Ecosystem Multifunctionality

“…LECs that are comprised of multiple species demonstrated higher levels of multifunctionality at low-medium levels compared to monocultures, due to the advantage of including species that are effective in several ecosystem functions (Riis et al, 2018) and complementarity in timing of growth that ensures functions are better delivered (Luo et al, 2023;Manolaki et al, 2020). However, as the performance threshold became higher (75 %), the monoculture plant community (e.g., Typha latifolia) was most effective.…”

“…Assembling plants in mixed stature communities appears to negatively influence above-ground tissue concentrations of nutrients/major ions, likely due to antagonistic interactions between large emergent species and smaller species (Luo et al, 2023). Additionally, the water in the mesocosm containing the MECs had comparatively higher levels of dissolved oxygen suggesting lower productivity and root turnover.…”

“…Measures of ecosystem functionality often aim to represent the ability of plant communities to simultaneously provide ecosystem functions into a single metric, whereas plant community phytoremediation has the potential to deliver multiple levels of ecosystem multifunctionality. To improve ecosystem functioning, and multifunctionality, and increase the ecosystem service provision of phytoremediation, it is important to optimise the composition of the plant community both in terms of its species richness and the functional traits of the component species (Carrillo et al, 2023;Luo et al, 2023). Generally, in terrestrial ecosystems two competing relationships are hypothesised to understand how community composition influences ecosystem function: (1) the mass ratio hypothesis, which proposes that ecosystem functioning is determined by the traits of the most dominant species (species identity) and (2) complementarity effects, which highlight the importance of species and functional diversity leading to reduced competition and increased resource partitioning (Garnier et al, 2016).…”

Phytoremediation Performance with Ornamental Plants in Monocultures and Polycultures Conditions Using Constructed Wetlands Technology

“…At the effluent, they were 4-10 mg/L and 0-3 mg/L, respectively (Figure 2), except for ammonia (average 80.8 ± 8.7 mg/L) and phosphate (average 86.7 ± 10.6 mg/L), the pollutant measured did not show statistically (p > 0.05) different removal rate between polycultures and monocultures with Canna hybrids (75-80%; p > 0.05), compared with the removal in monoculture CWs of Dieffenbachia seguine (63-68%; p < 0.05). Luo et al [35] indicated that plant communities with various growth forms reduced the intensity of interspecific competition, increased functional diversity, and greatly enhanced the ability to consume nitrogen and phosphorous compounds.…”

Research on Synergistic Development between Environment and Industry in the Yellow River Basin

“…This promotes the evolution of entities or systems through a certain dynamic regulatory mechanism to achieve coordinated and synchronized development. Current research on synergistic development focuses on various areas, including regional economic or city cluster synergistic development [13][14][15][16], industrial synergistic development [17][18][19][20], and synergistic development of economic-environmental composite systems [21][22][23], among others.…”