研究柴达木盆地二龄 、三龄混播与单播紫花苜蓿群落地上生物量、生长速率、株高 、盖度的季节动态变化，结果表明，三龄紫花苜蓿生物量、生长速率均高于二龄，但株高间差异不显著(P＞0.05)。混播的盖度高于单播、三龄的盖度高于二龄。混播苜蓿的牧草保持稳定比例，单播则变化较大。 The seasonal dynamics of aboveground biomass, growth rate, plant height and cover of mixed and uni sown communities were studied in the second and third instar of Qaidam Basin. The results showed that the biomass and growth rate of the third-grade alfalfa were higher than those of the second But there was no significant difference between plant height (P> 0.05). Coverage mixed coverage higher than unicast, the cover of the third age is higher than the second age. Herbage mixed with alfalfa kept a stable proportion, while unicast changed a lot.