Research professor Korea university, Republic of Korea
Urban trees are a potential carbon sink. However, estimating their carbon sequestration potential is challenging because the growth of urban trees over time shows large variations depending on the planting environments and management practices such as pruning. This study aimed to 1) develop biomass allometric equations for eight major urban tree species, 2) estimate their mean annual DBH increments, and 3) derive their annual carbon sequestration potential per unit tree crown cover (CRW) by classifying the land-use type (street trees, urban parks, and other areas) in South Korea. A total of 253 trees were destructively harvested, and the stem and branch volumes of 2,855 trees were measured using a laser dendrometer. The mean annual DBH increment of street trees was estimated using DBH data measured in 2002 and 2022. For urban parks and other areas, the mean annual DBH increment was estimated using a linear regression between DBH and the years after planting. To calculate the CRW, the DBH and crown area of 4,157 trees were measured. R2 of the biomass allometric equations ranged from 0.68 to 0.97. Particularly for intensively pruned species, such as Ginko biloba and Platanus spp., R2 of street trees (0.70 and 0.88, respectively) was lower than that of urban parks (0.89 and 0.94, respectively). The mean DBH increment was highest in Zelkova serrata (0.92 cm yr-1) and lowest in Acer palmatum (0.51 cm yr-1). The CRW values (ton C ha-1 yr-1) showed significant variation among tree species, ranging from 1.25 for Platanus spp. to 6.96 for Chionanthus retusus. Additionally, within the same species, there were significant differences in CRW values depending on the land-use type (e.g., Pinus spp.: 6.52 for street trees, 3.21 for urban parks, and 4.39 for other areas). This study suggests that utilizing a combination of destructive and non-destructive sampling methods is a practical approach for estimating carbon sequestration potential of urban trees where destructive harvesting is heavily restricted. Additionally, the study found significant variances in CRW values between species and land-use classification. Therefore, it is crucial to take into account species composition and the effect of management practice when a single value is derived at the national level.
