The experiment was conducted in Inner Mongolia steppe located in 43°26′-44° 08′N, 116°04′-117°05′ E in 1989-1997. The grazing experiment design was 5 stocking rates (0.00, 1.33, 2.67, 4.00, 5.33 and 6.67 sheep·hm-2, but 0.00, 1.33, 2.00, 2.67, 3.33 and 4.00 sheep·hm-2 in 1990) with three 1 hm2 rotational paddocks per treatment. The sheep were Inner Mongolia fine sheep and the experiment was performed during warm seasons every year from May 20 to October 5. The objectives were to research the integrated influence of different stocking rates on plant diversity and to provide knowledge of its mechanism by the method of continuous monitoring of 8 years for the same grazing experiment rather than through spatial gradient.The results showed that using the method of 100 m sample line was suitable for estimating the abundance of plant species. Simpson index and evenness were better parameters to measure the influence of different stocking rates on plant diversity for Artemisia frigida community. The plant species abundance almost remained unchanged, but the plant diversity and evenness decreased as the stocking rate increased, and the community dominance increased with stocking rate during the 8 years‘ grazing under different stocking rates. The interaction of the preferred ingestion of grazing sheep with heavy stocking rate may be one of the key reasons resulting in the decrease of plant diversity and evenness. Grass proportion decreased with the increase of stocking rates and A. frigida community degraded further into Potentilla acaulis community under heavy grazing or over-grazing. The succession and plant diversity of A. frigia community under different stocking rates mainly depend on the dynamics of A. frigida, Cleistogenes squarrosa, Potentilla acaulis, Agropyron cristatum and Carex duriuscula populations; Cleistogenes squarrosa population is one of the 3 populations of maximum abundance under all stocking rates from 1989 to 1997.
不同放牧率对内蒙古冷蒿草原植物多样性的影响
汪诗平 李永宏 王艳芬 陈佐忠
（中国科学院植物研究所植被数量生态学开放实验室，北京100093）
摘要： 以 8年 ( 1989～ 1997)定位的放牧试验数据为基础 ,较全面分析了不同放牧率对冷蒿 (Artemisiafrigida)草原植物多样性和草场异质性的影响 ,并从内蒙古细毛羊选择性采食和植物适应策略的角度探讨其影响机制。研究发现 ,在进行冷蒿小禾草草原的物种丰富度调查时 ,10 0m的样线法是可行的 ;在探讨放牧对群落多样性的影响时 ,Simpson多样性指数和均匀度指数对放牧率大小的变化更敏感。经过连续 8年的放牧 ,不同放牧率对物种丰富度的影响不大 ,但植物多样性和均匀度随放牧率的增大而下降 ,群落优势度却随放牧率增大而增大 ;内蒙古细毛羊的选择性采食和较高放牧率的互作是导致植物多样性和均匀度下降及群落优势度上升的主要原因。冷蒿、糙隐子草（Cleistogenes squarrosa）、星毛委陵菜（Potentilla acaulis）、冰草（ Agropyron cristatum）和寸草苔（ Carex duriusula）在不同放牧率下的种群消长决定了冷蒿草原的放牧演退规律和植物多样性大小；尽管内蒙古细毛羊较喜食糙隐子草，但其种群在所有放牧率下均是多度最大的$ 个种群之一。
关键词： 内蒙古草原；冷蒿群落；放牧率；植物多样性
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