THE EFFECTS OF GRAZING ON AGE STRUCTURE IN CLONAL POPULATIONS OF AGROPYRON MICHNOI
放牧干扰对根茎冰草无性系种群年龄结构的影响

Agropyron michnoi is a typical clonal grass, its oldest tiller nodes represent four years of growth. The age structure of the tillers in clonal population are altered under grazing interference. The age structures of the clone populations were stable in both all-year grazing plots and in plots rested from grazing in summer and autumn, while populations expanded in both treatments over winter. Productivity and vegetative propagativity was largest on one ear old tillers while by four years, tillers lost all vegetative propagativity. Growth of the clone populations and the community were best predicted by the age structures of vegetative buds. The age structure of tillers in clonal populations remained stable if grazed all year round, while population expansion was retained under winter grazing and could be developed by grazing in the summer and in the autumn. An Agropyron michnoi -dominated community would be maintained under both treatments over winter, while a mixed community would persist under all-year grazing. There is tendency towards an Agropyron michnoi -dominated community in grazing plots rested from grazing over summer and autumn.