Can Leaf Water Content Be Estimated Using Multispectral Terrestrial Laser Scanning? A Case Study With Norway Spruce Seedlings

Research output: Contribution to journalArticleScientificpeer-review

Researchers

Research units

  • University of Helsinki
  • Finnish Geospatial Research Institute
  • University of Eastern Finland
  • Luke Natural Resources Institute Finland
  • University of Turku

Abstract

Changing climate is increasing the amount and intensity of forest stress agents, such as drought, pest insects, and pathogens. Leaf water content, measured here in terms of equivalent water thickness (EWT), is an early indicator of tree stress that provides timely information about the health status of forests. Multispectral terrestrial laser scanning (MS-TLS) measures target geometry and reflectance simultaneously, providing spatially explicit reflectance information at several wavelengths. EWT and leaf internal structure affect leaf reflectance in the shortwave infrared region that can be used to predict EWT with MS-TLS. A second wavelength that is sensitive to leaf internal structure but not affected by EWT can be used to normalize leaf internal effects on the shortwave infrared region and improve the prediction of EWT. Here we investigated the relationship between EWT and laser intensity features using multisensor MS-TLS at 690, 905, and 1,550 nm wavelengths with both drought-treated and Endoconidiophora polonica inoculated Norway spruce seedlings to better understand how MS-TLS measurements can explain variation in EWT. In our study, a normalized ratio of two wavelengths at 905 and 1,550 nm and length of seedling explained 91% of the variation (R-2) in EWT as the respective prediction accuracy for EWT was 0.003 g/cm(2) in greenhouse conditions. The relation between EWT and the normalized ratio of 905 and 1,550 nm wavelengths did not seem sensitive to a decreased point density of the MS-TLS data. Based on our results, different EWTs in Norway spruce seedlings show different spectral responses when measured using MS-TLS. These results can be further used when developing EWT monitoring for improving forest health assessments.

Details

Original languageEnglish
Article number299
Number of pages14
JournalFRONTIERS IN PLANT SCIENCE
Volume9
Publication statusPublished - 8 Mar 2018
MoE publication typeA1 Journal article-refereed

    Research areas

  • terrestrial laser scanning, tree health, drought stress, multispectral laser scanning, leaf water content, forest damage, Endoconidiophora polonica, INDUCED TREE MORTALITY, FUEL MOISTURE-CONTENT, RED-ATTACK DAMAGE, LIDAR DATA, SURFACE-TEMPERATURE, FOREST HEALTH, PLANT STRESS, VEGETATION, REFLECTANCE, INTENSITY

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