中文摘要：

分析不同放牧强度下植物群落中物种的空间分布特征,有助于阐明群落在放牧胁迫下的演替规律。该研究基于幂函数法则,探讨了不同放牧强度下短花针茅（Stipa breviflora）荒漠草原群落植物的频率和空间异质性。结果表明：不同放牧强度下物种空间分布与幂函数法则能很好地吻合;不同物种空间异质性具有特异性,随着放牧强度的增加,提高群落空间异质性的物种分别由无芒隐子草（Cleistogenes songorica）、冷蒿（Artemisia frigida）、短花针茅、银灰旋花（Convolvulus ammannii）等多个物种逐渐转变为以无芒隐子草、短花针茅为主的少数物种,同时,物种空间异质性大于群落空间异质性的物种数逐渐减少。

英文摘要：

Aims Our objectives were to determine whether exponential function law is suitable to fit different levels of plant spatial heterogeneity in Stipa breviflora desert steppe,and to elucidate the patterns of species and community spatial heterogeneity under different grazing intensities,for better understanding the influence of grazing on plant community diversity,productivity and stability.Methods An experiment with randomized complete block design was conducted at the study site with four treatments and three replications for each treatment. The treatments consisted of light grazing,moderate grazing,heavy grazing and no grazing,respectively. Samples were taken from 50 cm × 50 cm quadrates（L quadrate） at every 0.5 m along three 50 m line transects,and totally 100 quadrates were measured. Each L quadrate was equally separated into four 25 cm × 25 cm smaller quadrates（S quadrate）. All species appeared in the S quadrates were recorded at the peak growth period. The exponential function law was used to fit the data in different grazing treatments.Important findings Results showed that the species studied had good concordance with exponential function law under different grazing intensities. With increases in grazing intensity,based on the species occurrence frequency,plant community gradually shifted from a mixture of Stipa breviflora,Cleistogenes songorica,Artemisia frigida,Salsola collina to mixed Stipa breviflora and Cleistogenes songorica. The spatial heterogeneity was species-specific in different grazing treatments. With increasing grazing intensity,the plant species with increased spatial heterogeneity gradually reduced from Cleistogenes songorica,Arternisia frigida,Stipa breviflora,Convolvulus ammannii,Salsola collina,Allium mongolicum,Leymus chinesis,Chenopodium aristatum,and Haplophyllum dauricum to only Cleistogenes songorica and Stipa breviflora. The number of species with greater spatial heterogeneity than community spatial heterogeneity deceased from the control to theheavy grazing treatment.