volume by integrating them into new allometric models. Declaration of competing interest The authors declare that they have no known competing finan- cial interests or personal relationships that could have appeared to influence the work reported in this paper. Data availability Data associated with this article is available at http://dx.doi.org/10.16904/envidat.403.Acknowledgements The authors would like to thank everyone involved in the WSL project ‘‘SwissBiomass’’, in the course of which the data used in this study were collected. In particular, we thank Marina Beck for project coordination, as well as all those who helped with the field and lab- oratory measurements. We also thank Daniel
Open resource ↗envidat · 10.16904/envidat.403 · pdf-raw-page:11 lines:1-93Paper record
Individual tree volume estimation with terrestrial laser scanning: Evaluating reconstructive and allometric approaches
Agricultural and Forest Meteorology. · 1 Oct 2023 · 10.1016/j.agrformet.2023.109654
Abstract
Accurate estimates of above-ground tree biomass within forest inventories are essential for calibration and validation of biomass mapping products based on Earth observation data. Terrestrial laser scanning (TLS) enables detailed and non-destructive volume estimation of individual trees, which can be converted to biomass with wood basic density. Existing TLS-based approaches range from simple geometrical features to virtual 3D reconstruction of entire trees. Validating such approaches with weight measurements is a key step before the integration of TLS or other close-range technologies into operational applications such as forest inventories. In this study, we firstly evaluate individual tree volume estimation approaches based on 3D reconstruction through quantitative structure models (QSM) against destructive reference data of 60 trees and compare them to operational allometric scaling models (ASM). Secondly, we determine the explanatory power of TLS-derived geometric parameters regarding total wood, stem, coarse wood and fine branch volume. We observe similar accuracy in merchantable (¿7 cm) wood compartments for ASMs (NRMSE = 25 %) and QSMs (NRMSE = 29 %), with QSMs showing better results for broadleaves than conifers and generally overestimating fine branch volume. Feature selection shows that a combination of stem diameters and volume of convex hulls around tree crowns has the most potential to model the entire tree volume including branches, especially for conifers. In cases where the quality of available point clouds is insufficient for QSMs, 3D information can thus still be utilised by deriving geometric parameters. The integration of crown dimension parameters into new allometric models could substantially improve the estimation of branch wood volume.
Code and data availability