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Estimation of vegetation water content at leaf and canopy level using dual-wavelength commercial terrestrial laser scanners

Lookup NU author(s): Ahmed Elsherif, Dr Rachel Gaulton, Professor Jon Mills

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Abstract

© 2018 The Author(s) Published by the Royal Society. All rights reserved. Vegetation water content, quantified as the leaf equivalent water thickness (EWT), can serve as an indicator of vegetation stress. The intensity data recorded by terrestrial laser scanning (TLS) instruments, operating at shortwave infrared wavelengths, can be used to estimate the three-dimensional distribution of EWT, after a full and rigorous calibration for the range and incidence angle effects. However, TLS instruments do not record the incidence angles automatically, making calibration challenging. In this study, intensity data from two commercially available TLS instruments (Leica P40, 1550 nm shortwave infrared wavelength, and Leica P20, 808 nm near-infrared wave-length) were combined in a normalized difference index (NDI). The NDI was found to minimize the incidence angle effects with no need for further calibration. A dry-down experiment was conducted using deciduous and conifer canopies. The NDI was found to be highly correlated to EWT at leaf level (R2 of 0.91 and 0.74) and at canopy level (R2 of 0.89 and 0.74) for the deciduous and conifer canopies, respectively. Three-dimensional distributions of EWT at canopy level were generated, which revealed some vertical heterogeneity.


Publication metadata

Author(s): Elsherif A, Gaulton R, Mills J

Publication type: Article

Publication status: Published

Journal: Interface Focus

Year: 2018

Volume: 8

Online publication date: 16/02/2018

Acceptance date: 06/12/2017

ISSN (print): 2042-8898

ISSN (electronic): 2042-8901

Publisher: Royal Society Publishing

URL: https://doi.org/10.1098/rsfs.2017.0041

DOI: 10.1098/rsfs.2017.0041


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