The spectral responses of a submerged plant <Emphasis Type="Italic">Vallisneria spiralis</Emphasis> with varying biomass using spectroradiometer

The relationship between land features and their spectral characteristics is a key for the interpretation of remote sensing images. This study was designed to investigate the spectral responses of Vallisneria spiralis, a common submerged aquatic plant in Shanghai, with varying biomass both in the laboratory and in the Middle Lake section of a field-scale constructed wetland, using a FieldSpec™ Pro JR Field Portable Spectroradiometer. The results showed that the reflectance rate of V. spiralis increased with its increasing biomass, and this was exhibited both at the visible band (500–650 nm) and the near infrared band (700–900 nm). The water environment influenced the reflectance rate and the primary differences between the laboratory and field results mainly occurred at the near-infrared band (700–900 nm). A regression analysis was carried out between the biomass of V. spiralis and the reflectance rate at the wavelengths of QuickBird™ bands where the biomass responded most strongly. The results of this analysis showed a clear linear relationship by which the biomass of V. spiralis could be quantitatively deduced from the reflectance rate measured in situ. The implications of this observation, in terms of the ability of hyperspectral remote sensing to estimate and monitor the distribution and dynamics of submerged aquatic vegetation on a large scale, are discussed. Handling editor: S. M. Thomaz