Estimating Urban Tree Volume and Carbon Storage Using Terrestrial Laser Scanning

Urban trees are important carbon sinks, but conventional allometric equations based mainly on diameter at breast height may not adequately represent their diverse three-dimensional structures. This study developed a terrestrial laser scanning (TLS)-based approach to estimate tree volume and carbon storage, including roots. The evergreen conifer Pinus thunbergii and the evergreen broadleaf tree Quercus myrsinifolia were scanned using TLS and subsequently harvested in the field. TreeQSM and AdQSM were applied to the resulting point clouds, and their accuracy in reproducing tree dimensions and stem volume was evaluated. TreeQSM showed better agreement with field measurements than AdQSM. Species-specific carbon storage models were developed using TreeQSM-derived stem and aboveground volumes. Both variables significantly explained carbon storage, although their explanatory power differed between species. The stem volume model performed better for P. thunbergii, whereas the aboveground volume model showed greater explanatory power for Q. myrsinifolia. These differences may reflect species-specific tree architecture and biomass allocation patterns. By linking TLS-derived volume metrics with directly measured carbon storage, including excavated roots, this study underscores the potential of a nondestructive approach to estimating carbon storage while accounting for the actual 3D structure of urban trees.