放牧干扰对根茎冰草无性系种群年龄结构的影响

根茎冰草（Agropyron michnoi)是典型的无性系禾草。在松嫩平原，根茎冰草的分蘖节最老为４龄，可存活５个年度。不同季节的放牧干扰可导致根茎冰草无性系种群分蘖株的年龄结构发生变化，全年放牧样地和夏秋休牧样地均为稳定型年龄结构,两个冬季放牧样地均为增长型年龄结构。１龄分蘖株的生产力和营养繁殖力力均最大。４龄分蘖株均已丧失了营养繁殖力。营养繁殖芽的年龄结构可以更好地预测预报无性系种群和群落的未来。全年放牧可保护稳定型年龄结构，冬季放牧可保持增长型年龄结构，夏秋休牧可使种群发展为增长型年龄结构，两个冬季放牧样地将仍然保持单优势种群落，全年放牧地将仍为混生群落，夏季林牧样地具有向着单优势种群落演替的潜在趋势。

THE EFFECTS OF GRAZING ON AGE STRUCTURE IN CLONAL POPULATIONS OF AGROPYRON MICHNOI

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.