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

Frontiers in Plant Science

Markus Holopainen¹  Samuli Junttila¹  Hannu Hyyppä²  Junko Sugano³  Harri Kaartinen⁴  Juha Hyyppä⁵  Antero Kukko⁵  Riikka Linnakoski⁶  Mikko Vastaranta⁷ 

[1] Centre of Excellence in Laser Scanning Research, Finnish Geospatial Research Institute (FGI), Masala, Finland;Department of Built Environment, Aalto University, Aalto, Finland;Department of Forest Sciences, University of Helsinki, Helsinki, Finland;Department of Geography and Geology, University of Turku, Turku, Finland;Department of Remote Sensing and Photogrammetry, Finnish Geospatial Research Institute (FGI), Masala, Finland;Natural Resources Institute Finland (Luke), Helsinki, Finland;School of Forest Sciences, University of Eastern Finland, Joensuu, Finland;

关键词: terrestrial laser scanning;    tree health;    drought stress;    multispectral laser scanning;    leaf water content;    forest damage;   

DOI  :  10.3389/fpls.2018.00299

来源: DOAJ

【 摘 要 】

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 (R2) in EWT as the respective prediction accuracy for EWT was 0.003 g/cm2 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.

【 授权许可】

Unknown