Investigation of above-ground biomass with terrestrial laser scanning : A case study of Valls Hage in Gävle

Sammanfattning: The thesis investigates above-ground biomass (AGB) with terrestrial laser scanning (TLS) for estimating AGB in a study area in Valls Hage, Gävle. The study used TLS for field measurements to collect highly detailed point clouds of two tree species for AGB estimation and comparison against validation data. TLS-derived data were validated using a non-destructive method involving direct field measurements using tape measures and a Trimble SX12 for extracting diameter at breast height (DBH), tree height, and crown diameter. Wood density was obtained from the literature. Data processing for segmentation, filtering, and generation of the quantitative structure model (QSM) was performed by using SimpleForest tool in Computree software. A statistical analysis was performed using linear regression, and AGB was estimated using QSM-derived volume multiplied by wood density. The finding in the results for the comparison of AGB estimation between TLS QSM and field validation from DBH-based tree-specific allometric equation had an RMSE of 154 kg, with a near-perfect agreement of 0.997 %, and RMSE of 189 kg, with the agreement of 0.990% for TLS QSM and TLS validation DBH-based tree specific equation. The comparison between TLS-derived DBH and field validation was accurate, leaving with insignificant differences, while the tree height had noticeable differences, and crown diameter had relatively low differences. The challenges during data processing were highlighted and the importance of TLS data for accurate AGB estimation, with the potential for refinement and integrating internal tree structure information to improve allometric models for future studies.