The structure characteristics of the communities under manmade forests were surveyed at three different attitudes in Jiuzhoutai District of Lanzhou City based on typical sampling strategy.The characteristics of species diversity were then analyzed based on the survey results.The results indicated that the communities on the midslope(altitude1 760-1 840 m) had the highest species diversity indices(DHJ)

the most species

and the best recovery degree.The layers of shrub and herb on the upslope(1 900-1 970 m) showed the lowest richness index

while the layers of shrub and herb on the downslope(1 590-1 730 m) showed the highest.The development of herbaceous layer was apparently better than the layers of shrubs and woods on the north mount according to the richness index

the species composition and biodiversity.The succession of communities was still at their early stages at all the slope positions

as implied by the dominant sunny species under the woody layer.The research on the biodiversity of manmade ecosystem at different altitudes was the extension of eco-afforestation project carried out on the north and south mounts;the findings from this study is of great importance for evaluating the effectiveness of vegetation recovery and reconstruction on the north and south mounts.