Abstract: Analysis into the unique spectral features of the ground objects can effectively identify the ground objects by using hyperspectral remote sensing technology. In the present study, the Caofeidian wetland in Tangshan City, Hebei Province was selected as the research object. The spectral characteristics of two typical wetland vegetations, Suaeda salsa (L.) Pall. and Phragmites australis(Cav.)Trin.ex Steud., were identified by SR2500 portable ground spectrometer. The original reflectance spectral curves of the two wetland vegetations and the reflectance spectral curves transformed by the envelope removal method were studied. It was shown that, due to the limitation of the envelope removal method, it was easier to distinguish the growth curve of the original vegetation of Phragmites australis in the range of 340-380 nm and 716-1 020 nm. In the range of 340-595 nm and 710-920 nm, the analysis of the original spectral curve of Suaeda salsa was more favorable to distinguish the growth periods. The reflectivity of the two vegetations in the vigorous growth period was higher than that in the terminal growth period. The envelope removal method at 508, 550 , 678 nm could better distinguish the growth periods of Phragmites australis, and the method of envelope removal at 638, 678 nm could better distinguish the growth periods of Suaeda salsa. For the two vegetations, the Phragmites australis had a distinct reflection peak at 550 nm in the green light band, while the Suaeda salsa had an obvious reflection peaks at 638 nm in the red light band, which made the two vegetations easier to distinguish after the treatment of envelope removal. In the range of 753-1 020 nm, the analysis of the original spectral curve was more suitable to distinguish the two vegetations, and the reflectivity of Phragmites australi was higher than that of Suaeda salsa.

Key words: hyperspectral remote sensing, Phragmites australi (Car.) Trin. ex Steud., Suaeda salsa (L.) Pau., spectral characteristics, envelope removal