Carbon Sequestration of Common Garden Tree Species under the Carbon Neutrality Target in East China

The global warming phenomenon caused by greenhouse gas emission leads to the deterioration of the ecological environment. In urban spaces, the selection of garden tree species with high carbon sequestration rates can effectively contribute to carbon neutrality. In this study, we measured the height, diameter at breast height, and crown width of 643 ancient trees around the West Lake Scenic Spot, Hangzhou, China, and recorded their species and ages. By the biomass expansion factor method, the long-term carbon sequestration of the trees was calculated, and the corresponding statistical analysis indicated the following findings: (1) The maximum carbon sequestration of ancient trees varies with the species; the simple rational function has the best fit for the relationship between mean annual carbon sequestration and age. (2) For the five most common species in the Hangzhou area, the total individual amount of carbon sequestration per tree species can be ranked from high to low as follows: Celtis julianae, Cinnamomum camphora, Castanopsis sclerophylla, Liquidambar formosana, and Ginkgo biloba (tree age < 260 years). The ranking for trees aged above 260 years is as follows: Celtis julianae, Cinnamomum camphora, Liquidambar formosana, Castanopsis sclerophylla, and Ginkgo biloba. (3) The transient and mean annual carbon sequestration rate decreases as tree age increases; for most of the ancient trees in this research, the main growing period is 0-300 years. (4) Castanopsis sclerophylla, Liquidambar Formosana, and Osmanthus fragrans are recommended for urban landscape greening as they provide continuous long-term carbon sequestration and special landscape features.