LAUSR

Atmospheric CO2 levels have been increasing with increasing industrialization. Studies have shown the growth response of various plant species to climate change and increasing CO2 levels, but variations in phytoremediation caused by elevated CO2 levels, especially in intercropping systems, have rarely been reported. The current study therefore revealed variations in the phytoremediation effect of Festuca arundinacea intercropped with Echinochloa caudata, a pernicious annual weed, exposed to various CO2 levels (280, 400, and 550 ppm). The biomass yield and Cd uptake capacity of monocultured F. arundinacea were found to increase with increasing atmospheric CO2 level, highlighting the promoted phytoremediation efficiency of this species under elevated CO2 levels. Elevated CO2 levels also significantly increased the dry weight of monocultured E. caudata but did not change the Cd content in various parts of the plant. However, the intercropping system decreased the biomass yield of belowground and aerial parts of F. arundinacea under all treatments, since E. caudata competed with it for water and nutrients. The weight reduction of F. arundinacea in the intercropping system increased with increasing CO2 level, because elevated CO2 significantly increased the competitiveness of the weed. Therefore, the Cd phytoremediation efficiency of F. arundinacea intercropped with E. caudata exposed to 280, 400, and 550 ppm CO2 decreased by 46.1%, 81.5%, and 215.0%, respectively, as evidenced by the decreased dry weight of F. arundinacea. Therefore, elevated CO2 levels could decrease the phytoremediation effect of F. arundinacea in fields where weed growth is unavoidable.