中文摘要：

六盘山位于陕甘宁交接地区，属于半湿润气候向半干旱气候的过渡带，是黄土高原生物多样性最丰富的地区之一，有维管植物836种，隶属于93科，359属。本区属于泛北极植物区、中国-日本森林植物亚区、华北植物地区的黄土高原亚地区。全部种子植物可分为13个分布区类型和12个变型，以北温带分布类型为主，与其他植物区系联系广泛，但特有属较贫乏。六盘山与小陇山、太白山和中条山的属相似性系数较高，均达60％以上，表明几座山体处于相似的生物气候背景之下，地理隔离性不明显。与贺兰山的属相似性系数低于60％，因为贺兰山位于干旱的荒漠与半荒漠区，可能有地理隔离作用。

英文摘要：

The Liupan Mountains are situated in the intersection of Ningxia Hui Autono- mous Region, Shaanxi, and Gansu provinces, between 35°- 36°10′N and 105°4′- 106°30′E. The region is not only the transitional zone between semi-humid and sub-arid climate, but also has rich biodiversity on the Loess Plateau, even in Northwest China, with regional vegetation distributing from warm temperate deciduous board-leaved forest zone, forestgrassland zone to desert-grassland zone. Studies on the plants＇ floras of Liupan Mountains show that it comprises 836 species of vascular plant, belonging to 93 families and 359 genera. Its floras can be attributed to the following categories. Loess Plateau subregion, North China region, Sino-Japan forest subkingdom, and Holarctic kingdom. There are 13 distribution types and 12 subtypes of genera of seed plants, of which North temperate elements play an important role in the flora. The plant genera flora on Liupan Mountains connect closely with other floras but have little endemic genera. The floristic affinities of the study area with neighboring three mountains （Taibai, Xiaolong and Zhongtiao mountains） are close, and their coefficients of plant genera flora all exceed 60%, indicating that these mountains have similar bio-climatic conditions without any clear vicariance. While the coefficient with Helan Mountains is under 60%, because the Helan Mountains are located in arid desert and semi-desert region and it is supposed that there is intense vicariance in nature in the development of the Yellow River in Ningxia and Gansu.