Abstract: Caragana auruntiaca, a dwarf legume shrub, only distributes in the Tekes riparian zone of Yili Valley in China. There is limited information on the age structure of C. auruntiaca young populations. In this study, two plots, an enclosure plot (Jiefang Bridge) and a grazed plot (76 Tuan), were set up in the concentrated distribution area of C.auruntiaca along the Tekes River. Three types of habitats, i.e. riverbank, floodplain and terrace, were selected in each plot, and three quadrats (20 m×20 m) were set up within each habitat. The age of young populations were identified by bud scale scar. The age structure of C.auruntiaca young population under two management regimes was examined, and the effects of soil factors on the age structure of juvenile plants was analyzed. In the enclosure plot, there were no 1-3 year-old seedlings, and the number of juvenile plants was concentrated in 5-10 yearold, suggesting the population belonged to the declining age structure in all the three habitats. In grazed plot, young populations in terraces and riparian habitat had declining age structure, while those in floodplain and in general had increa-sing age structure. Seedlings (1-5 year-old) were closely related to soil available nitrogen content, while trees (6-11 year-old) were closely related to soil available phosphorus content. The shrub ramet population was the most in 1-5 year-old, accounting for 69.9%, which belonged to increasing age structure. In the future management of C. auruntiaca shrub ecosystem, it is feasible to use moderate grazing to increase soil available nitrogen content, reduce forb coverage between shrubs, facilitate seed germination and seedling growth of C. auruntiaca, and promote population regeneration.C. auruntiaca can compensate for the negative effects from the decline of seedling population through vegetative reproduction, and thus could maintain the dominance of population number and its status as a constructive species.

Key words: corn rootassociated bacterial community, LNA-PCR, pyrosequencing, soil amendment, soil erosion.