Terrestrial laser scanning intensity captures diurnal variation in leaf water potential

• Published in: Remote sensing of environment 2021-03, Vol.255, p.112274, Article 112274
• Main Authors: Junttila, S., Hölttä, T., Puttonen, E., Katoh, M., Vastaranta, M., Kaartinen, H., Holopainen, M., Hyyppä, H.
• Format: Article
• Language: English
• Subjects: Diurnal variation; Diurnal variations; Drought; Dynamics; Laser applications; Lasers; Leaf water content; Leaf water potential; Leaves; Lidar intensity; Mortality; Plant species; Plant water dynamics; Position measurement; Remote sensing; Scanning; Terrestrial environments; Terrestrial laser scanning; Tree health; Trees; Water potential; Water stress
• ISSN: 0034-4257; 1879-0704
• DOI: 10.1016/j.rse.2020.112274

During the past decades, extreme events have become more prevalent and last longer, and as a result drought-induced plant mortality has increased globally. Timely information on plant water dynamics is essential for understanding and anticipating drought-induced plant mortality. Leaf water potential (ΨL), which is usually measured destructively, is the most common metric that has been used for decades for measuring water stress. Remote sensing methods have been developed to obtain information on water dynamics from trees and forested landscapes. However, the spatial and temporal resolutions of the existing methods have limited our understanding of the water dynamics and diurnal variation of ΨL within single trees. Thus, we investigated the capability of terrestrial laser scanning (TLS) intensity in observing diurnal variation in ΨL during a 50-h monitoring period. We aimed to improve the understanding on how large a part of the diurnal variation in ΨL can be captured using TLS intensity observations. We found that TLS intensity at the 905 nm wavelength measured from a static position was able to explain 77% of the variation in ΨL for three trees of two tree species with a root mean square error of 0.141 MPa. Based on our experiment with three trees, a time series of TLS intensity measurements can be used in detecting changes in ΨL, and thus it is worthwhile to expand the investigations to cover a wider range of tree species and forests and further increase our understanding of plant water dynamics at wider spatial and temporal scales. •Laser intensity metrics explained 56–77% of the variation in leaf water potential.•The 905 nm wavelength showed better performance compared to the 1550 nm wavelength.•Best-performing intensity metrics differed between species.