Exploring the dependence of spectral properties on canopy temperature with ground-based sensors: implications for synergies between remote-sensing VSWIR and TIR data

Halios, C. H. ORCID: https://orcid.org/0000-0001-8301-8449, Smith, S. T. ORCID: https://orcid.org/0000-0002-5053-4639, Pickles, B. J. ORCID: https://orcid.org/0000-0002-9809-6455, Shao, L. ORCID: https://orcid.org/0000-0002-1544-7548 and Mortimer, H. (2025) Exploring the dependence of spectral properties on canopy temperature with ground-based sensors: implications for synergies between remote-sensing VSWIR and TIR data. Sensors, 25 (3). 962. ISSN 1424-8220 doi: 10.3390/s25030962

Abstract/Summary

Spaceborne instruments have an irreplaceable role in detecting fundamental vegetation features that link physical properties to ecological theory, but their success depends on our understanding of the complex dynamics that control plant spectral properties—a scale-dependent challenge. We explored differences between the warmer and cooler areas of tree canopies with a ground-based experimental layout consisting of a spectrometer and a thermal camera mounted on a portable crane that enabled synergies between thermal and spectral reflectance measurements at the fine scale. Thermal images were used to characterise the thermal status of different parts of a dense circular cluster of containerised trees, and their spectral reflectance was measured. The sensitivity of the method was found to be unaffected by complex interactions. A statistically significant difference in both reflectance in the visible (VIS), near-infrared (NIR), and shortwave infrared (SWIR) bands and absorption features related to the chlorophyll, carotenoid, and water absorption bands was found between the warmer and cooler parts of the canopy. These differences were reflected in the Photochemical Reflectance Index with values decreasing as surface temperature increases and were related to higher carotenoid content and lower Leaf Area Index (LAI) values of the warmer canopy areas. With the increasingly improving resolution of data from airborne and spaceborne visible, near-infrared, and shortwave infrared (VSWIR) imaging spectrometers and thermal infrared (TIR) instruments, the results of this study indicate the potential of synergies between thermal and spectral measurements for the purpose of more accurately assessing the complex biochemical and biophysical characteristics of vegetation canopies.

Item Type	Article
URI	https://reading-clone.eprints-hosting.org/id/eprint/120674
Identification Number/DOI	10.3390/s25030962
Refereed	Yes
Divisions	Life Sciences > School of Biological Sciences > Ecology and Evolutionary Biology Science > School of the Built Environment > Energy and Environmental Engineering group
Uncontrolled Keywords	thermal measurements; spectral reflectance; synergy; vegetation canopy; absorption features; remote sensing; PROSAIL; carotenoids; LAI
Publisher	MDPI
Download/View statistics	View download statistics for this item