How much carbon can shrubs store? Measurements and analyses from Finland

Effective sequestration of carbon from the atmosphere is essential to combating climate change. Many cities have set ambitious carbon neutrality goals, highlighting the significance of urban vegetation as a carbon sink. Integrating urban vegetation into the urban form involves a multi-stage decision-making process, with planning and design playing a key role in the determination of space allocation and plant species selection. While carbon-smart design decisions are often based on emission databases and environmental product declarations (EPD), comprehensive data for urban vegetation is lacking. This study aims to assess carbon stocks in urban shrubs of Finland using dry-weight measurements. The measurements involve separating above- and below-ground parts of shrubs and assessing size indices (SIs). The results indicate species-specific differences in the proportion of root mass to total biomass. Furthermore, the below-ground biomass of plants spreading through sucking rhizome networks cannot be predicted by the size index. Although SIs do not directly describe below-ground biomass, they can predict the total dry weight. Generalising the data to shrub size categories provides an understanding of carbon stocks, but further research is essential, particularly for the process of implementing vegetation in urban settings. • Urban shrubs play a crucial role in carbon storage within urban vegetation systems. • Specific shrub size categories assist designers in optimizing urban carbon storage. • Shrub carbon content coefficients enhance the conversion of point cloud data into carbon stocks. • Shrub mass carbon storage per square meter should be assessed, not individual storage.