The spectral reflectance of coniferous tree stands and of barley influenced by stress : an analysis of field measured spectral data

Sammanfattning: This thesis focuses on the spectral signatures for vegetation. Knowledge about the spectral characteristics of different vegetation types is imperative for an efficient use of existing remote sensing systems, and also to provide guidelines for sensor development. In this work the relationship between the spectral reflectance factor and the object type, or the state of the object, is analyzed. Two different vegetation types have been studied, coniferous forest stands and barley fields. The spectral reflectance in the wavelength range 0.4—2.3 /tm for differently irrigated and fertilized plots of barley were measured during three years. The relationships between different spectral parameters and water status, biomass and grain yield are analyzed. A spectral parameter strongly related to the water status, but not to the biomass, is presented. The information content in the 1.3—2.3 µm range is discussed and it was found that the water content is only one of several factors governing canopy reflectance at these wavelengths. A method for making spectral reflectance measurements of forest stands from helicopter is described, and the spectral characteristics of stands of Norway spruce and Scotch pine with different ages, crown densities and field layers are discussed. The relationship between measurement geometry and spectral reflectance has also been studied.