关键词: 高寒草甸, 刈割频次, 初级生产力, 补偿效应

Abstract: Changes of basic characteristics of grassland primary productivity under different defoliation frequencies were studied at a typical alpine meadow in Maqu county,Gansu province.The results show that sedge and gramineous species had higher tolerance to frequent defoliation,forbs were more sensitive and some forb species even disappeared under high defoliation frequencies,while poisonous species were promoted under frequent defoliation disturbances.During the growing season,moderate and frequent defoliation(two or three times) in suitable ways did not cause adverse effects on species diversity but favored its increase.In contrast,it resulted to significant negative effects on species diversity if utilization occurred only once during the late periods of growth season(middle of September) or over four times during the whole growth season.For aboveground biomass,two times(July 15 and September 15) or three times(June 15,July 30,and September 15) were the optimum defoliation frequencies,and for protein output,three times was the optimum utilization way which led to a markedly higher protein content by 16.0% than those of two times(P<0.05).Stocking capability authorization of grassland at peak period of forage productivity must take account in the over-compensation effects produced in practice and revise forage productivity using corresponding variations.September 15) or three times(June 15,July 30 and September 15) were the optimum utilization frequencies,and for output of protein,three times was the optimum utilization way and markedly higher than two times(16%,P< 0.05).Checking stocking capability of grassland in the way of assessing output once at peak period of forage productivity must take account in over-compensation effects produced in practice and revise forage productivity using corresponding variations.

Key words: Alpine meadow, Defoliation frequency, Primary productivity, Compensation effect