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Article

Estimating Changes in Leaf Area, Leaf Area Density, and Vertical Leaf Area Profile for Mango, Avocado, and Macadamia Tree Crowns Using Terrestrial Laser Scanning

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Remote Sensing Research Centre, School of Earth and Environmental Sciences, the University of Queensland, Brisbane, QLD 4072, Australia
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The Joint Remote Sensing Research Program, Brisbane, QLD 4072, Australia
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Water Desalination and Reuse Center, King Abdullah University of Science and Technology, Thuwal 23955-6900, Saudi Arabia
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Precision Agriculture Research Group (PARG), University of New England, Armidale, NSW 2351, Australia
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Astron Environmental Consulting, 129 Royal Street, East Perth, WA 6004, Australia
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MacAvo Consulting, 84 Pashleys Road, Bundaberg, QLD 4670, Australia
*
Author to whom correspondence should be addressed.
Remote Sens. 2018, 10(11), 1750; https://doi.org/10.3390/rs10111750
Received: 2 October 2018 / Revised: 29 October 2018 / Accepted: 2 November 2018 / Published: 6 November 2018
(This article belongs to the Section Remote Sensing in Agriculture and Vegetation)
Vegetation metrics, such as leaf area (LA), leaf area density (LAD), and vertical leaf area profile, are essential measures of tree-scale biophysical processes associated with photosynthetic capacity, and canopy geometry. However, there are limited published investigations of their use for horticultural tree crops. This study evaluated the ability of light detection and ranging (LiDAR) for measuring LA, LAD, and vertical leaf area profile across two mango, macadamia and avocado trees using discrete return data from a RIEGL VZ-400 Terrestrial Laser Scanning (TLS) system. These data were collected multiple times for individual trees to align with key growth stages, essential management practices, and following a severe storm. The first return of each laser pulse was extracted for each individual tree and classified as foliage or wood based on TLS point cloud geometry. LAD at a side length of 25 cm voxels, LA at the canopy level and vertical leaf area profile were calculated to analyse tree crown changes. These changes included: (1) pre-pruning vs. post-pruning for mango trees; (2) pre-pruning vs. post-pruning for macadamia trees; (3) pre-storm vs. post-storm for macadamia trees; and (4) tree leaf growth over a year for two young avocado trees. Decreases of 34.13 m2 and 8.34 m2 in LA of mango tree crowns occurred due to pruning. Pruning for the high vigour mango tree was mostly identified between 1.25 m and 3 m. Decreases of 38.03 m2 and 16.91 m2 in LA of a healthy and unhealthy macadamia tree occurred due to pruning. After flowering and spring flush of the same macadamia trees, storm effects caused a 9.65 m2 decrease in LA for the unhealthy tree, while an increase of 34.19 m2 occurred for the healthy tree. The tree height increased from 11.13 m to 11.66 m, and leaf loss was mainly observed between 1.5 m and 4.5 m for the unhealthy macadamia tree. Annual increases in LA of 82.59 m2 and 59.97 m2 were observed for two three-year-old avocado trees. Our results show that TLS is a useful tool to quantify changes in the LA, LAD, and vertical leaf area profiles of horticultural trees over time, which can be used as a general indicator of tree health, as well as assist growers with improved pruning, irrigation, and fertilisation application decisions. View Full-Text
Keywords: terrestrial laser scanning; horticultural; leaf area; leaf area density; vertical leaf area profile terrestrial laser scanning; horticultural; leaf area; leaf area density; vertical leaf area profile
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MDPI and ACS Style

Wu, D.; Phinn, S.; Johansen, K.; Robson, A.; Muir, J.; Searle, C. Estimating Changes in Leaf Area, Leaf Area Density, and Vertical Leaf Area Profile for Mango, Avocado, and Macadamia Tree Crowns Using Terrestrial Laser Scanning. Remote Sens. 2018, 10, 1750. https://doi.org/10.3390/rs10111750

AMA Style

Wu D, Phinn S, Johansen K, Robson A, Muir J, Searle C. Estimating Changes in Leaf Area, Leaf Area Density, and Vertical Leaf Area Profile for Mango, Avocado, and Macadamia Tree Crowns Using Terrestrial Laser Scanning. Remote Sensing. 2018; 10(11):1750. https://doi.org/10.3390/rs10111750

Chicago/Turabian Style

Wu, Dan, Stuart Phinn, Kasper Johansen, Andrew Robson, Jasmine Muir, and Christopher Searle. 2018. "Estimating Changes in Leaf Area, Leaf Area Density, and Vertical Leaf Area Profile for Mango, Avocado, and Macadamia Tree Crowns Using Terrestrial Laser Scanning" Remote Sensing 10, no. 11: 1750. https://doi.org/10.3390/rs10111750

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