Abstract: By the method of geostatistics, this paper studied the spatial heterogeneity of plant community species diversity in Ejina Oasis at the lower reaches of Heihe River. In the study area, the Margalef richness index (M_a), Simpson diversity index (D_s), Shannon diversity index (H′) and Pielou evenness index (J′) were in normal distribution, and the coefficient of variation (CV) ranged from 55.8% to 67.8%, suggesting a moderate variability. The M_a and H′ were accorded with exponential models, and the D_s and J′ were accorded with spherical models. The H′ had the highest extent of spatial variation, followed by M_a, J′ and  D_s. Within the variable range, the structural factors in the spatial variation of M_a, D_s, H′, and J′ were dominant, ranging from 81.1% to 93.0%. The indices changed obviously parallel to the river, with significantly high values near Dalaihubu Town (42° N, 101° E), and obviously low values within the strips 100°-101° E and 102°-102°30′ E, mainly including east and west Gobi and the hinterland of Badain Jaran Desert.

Key words: species diversity, spatial heterogeneity, Ejina Oasis, Heihe River