Résumés
Abstract
Spectral reflectance measurements conducted during two field campaigns in west Greenland, and in the laboratory using samples collected during those campaigns, are discussed to evaluate the spectral signature of lichens. Given the diversity in lichen species, colors, and appearance — ranging from crust-like (crustose) to almost like mini shrubs (fructicose) — it is not surprising that no single signature was found. Some of the brighter fructicose lichens have reflectance characteristics very similar to those of green vegetation, with a pronounced rise in reflectivity around 750 nm. However, the most abundant lichen species covering rocks in the ice-marginal zone of west Greenland are dark grey to black crustose and foliose ephilithic (rock-growing) lichens and the shape of the reflectance spectrum for these lichens is generally very different from that of other surface types and landcovers, with near-zero reflectance at visible wavelengths, and a maximum around 1 600 nm. This characteristic allows rock-covered lichen to be identified on multispectral satellite imagery.
Résumé
L’évaluation de la signature spectrale des lichens est effectuée à partir de mesures prises en laboratoire et sur le terrain, au Groenland occidental. Aucune signature spécifique ne peut être identifiée, en raison de la diversité des espèces quant à leur couleur et à leur port, allant de la croûte à l’arbuste nain. Les lichens arbustifs les plus brillants montrent une signature spectrale semblable à celle des plantes vertes, avec un pic très prononcé autour de 750 nm. Toutefois, les lichens les plus abondants sur les roches à proximité des glaces sont gris foncés à noirs et du type crustacé ou foliacé; leur spectre de réflectance montre une allure très différente de celle des autres types de surface et de couverture, et se rapproche de zéro dans le spectre visible avec un pic autour de 1 600 nm. Cette caractéristique permet l’identification des roches recouvertes de lichens par l’imagerie satellitaire multispectrale.
Parties annexes
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