Abstract: Leymus secalimus,a species of typical clonal plant,is a long-rhizome grass.Under cultivated condition in the Songnen Plain of China,its transplanted single tiller could form 215 tillers at most by vegetative reproduction of a clone in a growth season,and the largest clone was 5.4 times of the smallest one among four sampling clones in the first year.In the second year,the largest clone could form 2852 tillers at most,which was 2.7 times of the smallest one in two growth seasons.At unitary level,the expanding area of the clones and the number of the tillers increased by 13.2 and 13.3 times,respectively,and the accumulative length,nodes number and rhizomes biomass increased by 15.9,11.2 and 14.7 times averagely by the end of the growth season in the second year than in the first year,respectively.The tillers consisted of two age classes and showed expanding age structure,which was more obvious with the growth of clones.The bud banks consisted of three age classes and showed expanding age structure,which decreased gradually with the growth of clones.The tillers could be developed through forming lots of topmost buds and node buds of rhizome,and the clones achieved the spatial niche expansion and repetitive regeneration.

Key words: Leymus secalimus, Vegetative reproduction generation, Tiller, Rhizome, Bud, Module, Age structure, Clone growth