Significant carbon storage and sequestration by urban greenery in Beijing city during 2010–2020

Abstract

As global urbanization continues, it has become increasingly important to understand the role of urban greenery in carbon (C) storage and sequestration for sustainable urban planning. However, due to a lack of long term field-based studies, the dynamic characteristics of C storage and sequestration by urban greenery over multiple years remain poorly understood. Here we developed specific allometric equations for various types of urban vegetation, and quantified the C storage and sequestration of urban greenery with different compositions of vegetation and landscape types across Beijing, from 2010 to 2020. This was based on field measurements from 604 sampling plots, combined with a dataset derived from the Urban Landscape Architecture Survey of Beijing. Our results showed that the biomass of urban vegetation (including various tree, shrub and bamboo species) could be well predicted using a combination of dendrometric variables, such as diameter at breast height (DBH), diameter at ground level (G), canopy width (W) or the height (H) of plants. Total (above- and below-ground) C storage by urban greenery increased from 2.6 Tg C (1 Tg = 10¹² g) in 2010–6.3 Tg C in 2020, with the C sequestration of 0.32–0.43 Tg C yr⁻¹. The C density of urban greenery varied from 4.1 to 6.9 kg C m⁻² between 2010 and 2020, representing an annual C sequestration rate of 0.20–0.34 kg C m⁻² yr⁻¹. Combining this with a similar estimate for Beijing’s urban greenery in 2005 revealed that between 2005 and 2020, the C storage and density of urban greenery increased linearly over time. However, the C sequestration or annual C sequestration rate initially increased and then diminished over 2005–2020, which is likely linked to changes in vegetation physiology and plant age structure. These findings emphasize the need for effective management, such as planting optimal native vegetation types and species to maximize local adaptation and C uptake, as well as the expansion of urban vegetation, to enhance C storage and sequestration, thereby offering valuable insights for leveraging urban greenery strategies to mitigate climate change.