Effect of Chlorophyll Content & Solar Irradiance on Spectral Reflectance of Vegetation Canopies Acquired By Spectro-Radiometer

Abstract

The aims of the study were: (i) to observe the effect of leaf chlorophyll content, Solar Irradiance and Normalized Difference Vegetation Index (NDVI) on spectral reflectance at Visible(Blue,Green,Red), Near Infrared (NIR) and Short Wave Infrared (SWIR) spectrum for a given number of vegetation types including Rongon (Ixora Coccinea), Hibiscus, Jhau, Grass and Togor(Tabernaemontana Divaricata).(ii) to investigate the relationship of Solar Irradiance with Normalized Difference Vegetation Index (NDVI) for the same number of vegetation types. This study used a five band hand-held spectro-radiometer “Multispectral Radiometer MSR-5” centered at wavelength 485nm, 560nm, 660nm, 830nm and 1650nm corresponding to bands 2, 3, 4, 5, 6 of Landsat 8 operational Land Imager (OLI) sensor. This spectro-radiometer provides solar irradiance and spectral reflectance values in the visible, NIR and SWIR spectrum which indirectly help to calculate Normalized Difference Vegetation Index (NDVI) for the given number of vegetation types. This study also used a Chlorophyll Meter (SPAD 502) to estimate chlorophyll concentration from the leaf of the vegetation types. The result shows that the value of the spectral reflectance correlated linearly with chlorophyll content at wavelength at 560nm and 1650 nm where the coefficient of determination R2 is 0.8761 and 0.6289 respectively. The spectral reflectance correlated inversely with NDVI at wavelength 485nm and 660nm where the coefficient of determination R2 was 0.5317 and 0.6191 respectively. This result also shows that solar irradiance relates inversely with chlorophyll content at wavelength 830nm where the coefficient of determination R2 was 0.8523.Lastly we have found that solar irradiance correlated inversely with NDVI where the coefficient of determination R2 was 0.7617.