Abstract: Based on the data investigated from the field,one richness index,two species diversity indices and two evenness indices were used to analyze the vegetation on the Bird Island of Qinghai Lake.In addition,relationships among these indices were studied by correlation analysis.There are some results:(1) The species diversity was much different between the seven main sand plant communities.Those distributed on fixed sand dunes had higher richness and diversity indices,such as Leymus secalinus and Clematis tangutic;indices of Polygonum sibiricum and Corispermum tibeticum on shifting sand dunes were the lowest,while the evenness indices were the highest.(2) In the gradient from shifting to fixed sand dune,the changing tendency of the richness index,Shannon-Wiener index and Simpson index showed almost the same,but the evenness indices showed the contrary tendency and semifixed sand dune was an important turning point.(3) The species frequent diversities on different sand dunes were different.Special species dominated on fixed sand dunes,the Shannon-Wiener index and Simpson index were the highest.But on shifting sand dunes,the common species diversity indices were the highest.(4) For all dune types the species diversity indices of perennial plants were the highest,those of annual plants were at the second,they increased from shifting sand dune stage to fixed stage.(5) There was very near correlation between the richness and species diversity indices or evenness indices.

Key words: Bird Island of Qinghai Lake, sandy plant community, species diversity