Towards the Remote Sensing of Matorral Vegetation Physiology: Relationships between Spectral Reflectance, Pigment, and Biophysical Characteristics of Semiarid Bushland Canopies

This study investigates the relationships between the spectral reflectance characteristics and the concentrations of photosynthetic pigments and biophysical attributes of a structurally complex, spatially heterogeneous vegetation canopy with varying background properties. A field experiment was performed in the Guadalentin basin, Spain using matorral vegetation canopies dominated by Rosmarinus officinalis, Cistus albidus, and Anthyllis cytosoides. A spectroradiometer was used to record the reflectance of a series of sites at which measurements were made of the concentrations per unit ground area and per unit leaf mass of chlorophyll a and b and the carotenoids, together with leaf area index and percent canopy cover. A range of spectral characteristics was examined which have been found previously to be related to pigment concentrations and biophysical properties of vegetation. For matorral vegetation many of these spectral characteristics were unrelated or only weakly related to canopy properties. However, it was found that pigment concentrations per unit ground area were related to ratios of reflectance in narrow spectral bands within the near-infrared region, ratios of bands within the red region, and characteristics of the amplitude of first derivative spectra in the red edge region. Pigment concentrations per unit leaf mass were correlated with ratios of bands around the nearinfrared “shoulder” and the amplitude of the first derivative in certain visible wavelengths. LAI and percent cover were related to ratios of reflectance in narrow bands on the near-infrared plateau and red edge features of canopy reflectance spectra, as well as with the amplitude of the first derivative in the red edge and visible regions respectively.