Carbon sequestration and CO₂ flux in six plant species in vertical greenery systems

The ecosystem services of vertical greenery systems (VGSs) have attracted increasing research attention in recent decades. In addition to improving urban landscape esthetic and thermal comfort, VGSs also contribute to carbon (C) sequestration and CO₂ uptake to mitigate climate change. In this study, the C storage and sequestration of six commonly used plant species (Coleus scutellarioides, Peperomia claviformis, Tradescantia spathacea, Duranta repens, Ficus elastica, and Heptapleurum heptaphyllum) in VGSs were determined over a year period. The C sequestration potential of the six plant species ranged from 60.6 to 248 g C m^− 2 yr^− 1, and T. spathacea was most effective in C sequestration. The net ecosystem CO₂ exchange (NEE) of each plant species during different seasons were measured by using a portable chamber. The results revealed significant seasonal patterns in NEE, with peaking values occurring in summer. Additionally, the NEE values were higher for woody plants than for herbaceous plants. Correlation analysis indicated that the NEE of the VGSs was significantly affected by leaf area index (LAI), root biomass, and stomatal conductance. In addition, the indoor CO₂ uptake rates of six plant species in VGSs were predicted under photosynthetically active radiation (PAR) = 200 and 450 µmol m^− 2 s^− 1. Among six plant species, H. heptaphyllum exhibited highest average indoor CO₂ uptake rate throughout four seasons. Therefore, optimizing VGSs with woody plants featuring high NEE and biomass is critical for enhancing C sequestration and CO₂ uptake within urban ecosystems.