Terrestrial laser scanning intensity captures diurnal variation in leaf water potential

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 (Psi(L)), 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 Psi(L) within single trees. Thus, we investigated the capability of terrestrial laser scanning (TLS) intensity in observing diurnal variation in Psi(L) during a 50-h monitoring period. We aimed to improve the understanding on how large a part of the diurnal variation in Psi(L) 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 Psi(L) 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 Psi(L), 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.

Automated summary

Extreme events in the past decades have led to an increase in drought-induced plant mortality globally. Timely information on plant water dynamics is crucial for understanding and predicting such mortality. Research has shown that using terrestrial laser scanning (TLS) intensity measurements can capture a significant portion of diurnal variation in leaf water potential (Psi(L)), enhancing our understanding of plant water dynamics.