Abstract: Plant diversity of natural grassland in hilly region of Loess Plateau in Gansu eastern was studied. 16 communities involved in 3 vegetation typies. Stipa bungeana steppe, secondary ruderal steppe and ruderal meadow steppe was determined according to species dominance index as well as the quadrats data of 30 vegetation sites. They can be divided into forbid grazing grassland, over grazing grassland and moderate grazing grassland. The Shannon-wiener index and Simpson index showed a trend of ruderal meadow steppe>Stepa bungeana steppe>secondary ruderal steppe, and moderate grazing grassland>forbid grazing grassland>over grazing grassland. Grazing degree may be the key factor that influences the diversity of natural communities in this region. It is a possible result of grazing disturbance that the diversity index decrease by the altitude heightens and precipitation increase. Correlation analysis showed that the Shannon-wiener index and Simpson index are significantly positively correlated with Shannon evenness index and Simpson evenness index, and are significantly negatively correlated with the biomass.

Key words: Loess Plateau, Gansu east, grassland community, plant diversity