Canopy Spatial Distribution and Identification Using Hyperspectal Data in Winter Wheat
2009
Lu, Yan-Li | Li, Shao-Kun | Bai, You-Lu | Jones, Carol L. | Wang, Ji-Hua
Winter wheat varieties (Triticum aestivum L.) with different leaf angle distributions (LADs) were used in this experiment. Results showed that varieties with planophile LADs had leaf orientation values (LOVs) ranging from 25.12 to 40.33, whereas varieties with erectophile LADs had LOVs ranging from 67.5 to 73.25. Canopy spectral reflectance was measured using a ground-based spectroradiometer. Correlation analysis indicated that LOV affected canopy spectra more than leaf area index (LAI) before the jointing stage. The LAI had the greatest effect after the ground was nearly completely covered. Discriminant analysis showed that simultaneous measurements of normalized difference vegetation index (NDVI) and cover can differentiate LADs in those wheat varieties with similar population magnitude at the jointing stage. In addition, by using increments of the canopy spectral reflectance at different growth stages, the planophile varieties with low LAIs can be differentiated from the erectophile varieties with high LAIs, which cannot be achieved using NDVI and cover. Using ΔR890 as the reflectance increment of booting stage and jointing stage and R890 as the reflectance of 890-nm energy at the jointing stage, different varieties presented distinctly different scatter plot representations (X = ΔR890, Y = R890). This analysis also indicted that varieties with different LADs can be clustered and identified qualitatively in the plot despite their population magnitude, also validated by discriminant analysis.
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