草原放牧系统持续管理试验研究:试验设计及放牧率对草-畜系统影响分析

在内蒙古典型草原区中国科学院草原生态定位站研究不同放牧率、放牧方式和放牧季节对草原植物和家畜生产的影响。结果表明,地上现存量随着放牧率的增加而降低,但达到峰值的日期提前了。地上生物量与放牧率无明显趋向性变化。家畜增重随着放牧率的增大而下降,公顷总增重与放牧率成二次曲线关系。将放牧率对草原生产力的动态确定为可持续放牧率和改良放牧率。

Grazing Experiment for Sustainable Management of Grassland Ecosystem of Inner Mongolia Steppe:Experimental Design and the Effects of Stocking Rates on Grassland Production and Animal Liveweight

A long-term experimental site of 24 paddocks of 1 ha was set up in 1989 in the true steppe area of central lnner Mongolia to study the effects of grazing management factors on composition and production of grasslands as well as animal performance.The grazing management factors include rates(5 levels:1.33,2.47,4.00,5.33 and 6.67 sheep/ha/season),grazing methods(rotational vs continuous;high stocking rate with short grazing duration vs low stocking rate with long grazing duration)and grazing season(spring,summer and autumm).The grassland was a pasture type true steppe vegetation dominated by Artemisia frigida,Cleistogenes squarrosa and Agropyron michnoi,etc..The whole experimental design and the features of the experimental system were described,but only the effects of stocking rate(SR)were analyzed using the first 4 years data.The phytomass composition of the experimental grassland has a significant change after the 4 year grazing under different SR,For example,Leymus chinensis and Agropyron michnoi significantly increased(P<0.05)at low SR or in the ungrazed control paddock,implying a vegetation succession towards the Leymus chinensis community;while Potentilla acculis increased largely at high SR,indicating a grassland degradation.The highest aboveground standing crops(SC)of the grassland during the growing season decreased,and their appearing date advanced,with the SR increase.While the aboveuground phytomass(production=SC+animal consumed phytomass)has no significant changing trend on the SR gradient.It suggested a very good plant regeneration after grazing.The data also demonstrated an over-compensatory growth of plants at low SR,but its existence,especlally its sustainability needs more research.The individual animal body weight gain linearly decreased with SR increase,and therefore the body weight gain per hectare has a quadric relation with SR.The SR having the maximum liveweight gain is useful per animal in grazing management.But the other meningful stocking rates for management were also discussed,including the SR for maximum economic income,SR for sustaining grassland rehabilitation.The results also suggested that long-term experimental data including interannual climatic variation were needed for defining these SR,understanding the effects of management,and proposing an approprlate management system.