中文摘要：

以陇东黄土高原丘陵沟壑区天然草地30个植被样点的样方资料为依据,以相对生物量为指标,对该地区群落植物多样性进行了研究.结果表明,该地区天然草地可划分为长芒草草原、次生杂类草草原和杂类草草甸草原3个植被类型,16个群落按放牧程度分为禁牧草地、轻牧草地和过牧草地3个层次.多样性指数显示草甸草原＞长芒草草原＞次生杂类草草原,轻牧草地＞禁牧草地＞过牧草地的趋势.放牧程度可能是影响该区域天然草地植物多样性的关键因素,出现海拔增高和降水增加多样性指数降低的趋势可能是放牧干扰的结果.相关性分析显示物种的Shannon-wiener和Simpson多样性指数与Shannon和Simpson均匀度指数间均呈显著正相关,而与生物量之间呈显著负相关.

英文摘要：

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 forbid grazing grassland bungeana steppe 〉 secondary ruderal steppe, and moderate 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 evenness index and Simpson evenness index, and are significantly positively correlated with Shannon significantly negatively correlated with the biomass.