[pp.87-96]

Importance of the Green Spectral Region for Remote Assessment of Tree Vigor Condition: A Case Study of Cerasus Species

Youngkeun SONG, Junichi IMANISHI, Hiroshi HASHIMOTO, Atsuo MORIMURA and Yukihiro MORIMOTO （Kyoto University / Meijo University / University of Human Environments）

Abstract:
To assess tree vigor condition at a broader scale, remote sensing is expected to be more efficient than traditional ground work. For vegetation indices, red and near–infrared wavelengths have widely been used; however, recent studies have highlighted the potential of other spectral regions, particularly “green” wavelengths. Using the published vegetation indices and other potential spectral combinations, derived from airborne remote sensing data, we examined the effective spectral region for assessing the tree vigor condition, in the case of 66 Cerasus trees. As a result, the ratio or the normalized difference of reflectance at the red–edge (700 nm) and green (541 nm) showed the highest correlation with tree vigor condition (rs = 0.659). Among the published indices, R750/R550, designed for estimating chlorophyll concentration, showed the strongest correlation with tree vigor condition (rs = 0.444). These results indicate that the green region, which is closely related to chlorophyll content, is an important indicator of tree vigor condition. The best–performing index (green with red–edge) was subjected to discriminant analysis to classify the trees into one of five ranks related to vigor condition. After 10 iterations, we obtained a mean accuracy of 84.5% with fuzzy logic, which could be useful in surveying the tree vigor condition over a broader area.

Key Word:
flowering cherry, Prunus, crown condition, tree health, vegetation indices, airborne remote sensing

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