Effects of plant diversity on carbon dioxide emissions and carbon removal in laboratory-scale constructed wetland

Abstract

Previous studies have shown that plant diversity can enhance methane (CH₄) emission and nitrogen purification efficiency in constructed wetlands (CWs), but effect of plant diversity on carbon dioxide (CO₂) flux and carbon removal efficiency in CWs is unknown. Therefore, we established four plant diversity levels (each level containing 4, 3, 2, and 1 species, respectively) in laboratory-scale wetland microcosms fed with simulated wastewater. Results showed that plant species richness enhanced CO₂ emissions (84.7–124.7 mg CO₂ m⁻² h⁻¹, P < 0.01), carbon fixation rate (P < 0.05), and microbial biomass carbon (P < 0.001), but did not improve carbon removal (P > 0.05). The presence of Pontederia cordata increased CO₂ emissions, carbon fixation rate of belowground, and microbial biomass carbon (P < 0.05), whereas the presence of Phragmites australis only enhanced CO₂ emission (P < 0.05). However, the presence of Typha orientalis or Lythrum salicaria did not show an influence on CO₂ emissions and carbon removal (P > 0.05). Hence, our study highlights the importance of plant diversity in mediating CO₂ emission intensity and carbon processes but not carbon removal in CWs.

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