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Article

Exploring the Variability of Tropical Savanna Tree Structural Allometry with Terrestrial Laser Scanning

1
Research Institute for the Environment & Livelihoods, College of Engineering, IT and Environment, Charles Darwin University, Casuarina, NT 0909, Australia
2
CSIRO Land and Water, PMB 44, Winnellie, NT 0822, Australia
3
CAVElab—Computational and Applied Vegetation Ecology, Faculty of Bioscience Engineering, Ghent University, 9000 Gent, Belgium
*
Author to whom correspondence should be addressed.
Remote Sens. 2020, 12(23), 3893; https://doi.org/10.3390/rs12233893
Received: 31 August 2020 / Revised: 25 September 2020 / Accepted: 19 November 2020 / Published: 27 November 2020
(This article belongs to the Special Issue Remote Sensing of Savannas and Woodlands)
Individual tree carbon stock estimates typically rely on allometric scaling relationships established between field-measured stem diameter (DBH) and destructively harvested biomass. The use of DBH-based allometric equations to estimate the carbon stored over larger areas therefore, assumes that tree architecture, including branching and crown structures, are consistent for a given DBH, and that minor variations cancel out at the plot scale. We aimed to explore the degree of structural variation present at the individual tree level across a range of size-classes. We used terrestrial laser scanning (TLS) to measure the 3D structure of each tree in a 1 ha savanna plot, with coincident field-inventory. We found that stem reconstructions from TLS captured both the spatial distribution pattern and the DBH of individual trees with high confidence when compared with manual measurements (R2 = 0.98, RMSE = 0.0102 m). Our exploration of the relationship between DBH, crown size and tree height revealed significant variability in savanna tree crown structure (measured as crown area). These findings question the reliability of DBH-based allometric equations for adequately representing diversity in tree architecture, and therefore carbon storage, in tropical savannas. However, adoption of TLS outside environmental research has been slow due to considerable capital cost and monitoring programs often continue to rely on sub-plot monitoring and traditional allometric equations. A central aspect of our study explores the utility of a lower-cost TLS system not generally used for vegetation surveys. We discuss the potential benefits of alternative TLS-based approaches, such as explicit modelling of tree structure or voxel-based analyses, to capture the diverse 3D structures of savanna trees. Our research highlights structural heterogeneity as a source of uncertainty in savanna tree carbon estimates and demonstrates the potential for greater inclusion of cost-effective TLS technology in national monitoring programs. View Full-Text
Keywords: allometry; biomass; carbon; cost-effective; LiDAR; TLS allometry; biomass; carbon; cost-effective; LiDAR; TLS
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  • Externally hosted supplementary file 1
    Link: https://github.com/LindaLuck/Luck2020Exploring
    Description: This repository contains the analysis scripts of Exploring the variability of tropical savanna tree structural allometry with terrestrial laser scanning.
MDPI and ACS Style

Luck, L.; Hutley, L.B.; Calders, K.; Levick, S.R. Exploring the Variability of Tropical Savanna Tree Structural Allometry with Terrestrial Laser Scanning. Remote Sens. 2020, 12, 3893. https://doi.org/10.3390/rs12233893

AMA Style

Luck L, Hutley LB, Calders K, Levick SR. Exploring the Variability of Tropical Savanna Tree Structural Allometry with Terrestrial Laser Scanning. Remote Sensing. 2020; 12(23):3893. https://doi.org/10.3390/rs12233893

Chicago/Turabian Style

Luck, Linda, Lindsay B. Hutley, Kim Calders, and Shaun R. Levick. 2020. "Exploring the Variability of Tropical Savanna Tree Structural Allometry with Terrestrial Laser Scanning" Remote Sensing 12, no. 23: 3893. https://doi.org/10.3390/rs12233893

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