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 (84.7-124.7mg CO2 m-2h-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.