关键词: 高寒沙地, 主要优势种群, 植被演替, 光谱分析, 西藏高原

Abstract: Bare sandlot, sparse herbaceous grasses, grass-shrub transition, and shrubbery are the major stages of vegetation succession on sandlots in alpine valleys of Tibet, China. Based on large volume of field surveys, vegetations on alpine valley sandlots were sorted into the four stages of the succession, and hyperspectra of the vegetations different in succession stage were obtained using an ASD Field Spec3 spectroradiometer during the field surveys for comparative analysis to determine hyperspectral characteristics of the dominant psammophyte community and variability between vegetations of different stages in spectrum. Results show that as key dominant psammophytic species for dividing stages of vegetation succession, Artemisia sphaerocephala, Hedysarum scoparium, Artemisia younghusbandii, Artemisia wellbyi, Hedysarum mongolicum, Sophora moorcroftiana, and Orinus thoroldii, varied significantly in hyperspectrum, and the variations manifest mainly in red edge position, red edge shape, red valley and cellulose absorption band. During the process of vegetation succession from bare sandlots to sparse herbaceous grasses, to grass-shrub transition, and to shrubbery, vegetation coverage of the psammophytic communities increased while bare sandlot decreased gradually in area; spectral reflectance on the whole kept on intensifying; the spectral feature of red valley caused by Chlorophyll absorption intensified; the near infreared moisture absorption valley strengthened; and the feature of soil background spectrum gradually weakened. Moreover, the spectra of the dominant psammophyte communities of various succession stages varied quite considerably in consistency.

Key words: alpine sandlot, main dominant population, vegetation succession, spectral analysis, Tibetan Plateau