Abstract: A test was conducted to determine the content of soil micro-biomass carbon and nitrogen on cultured pastures of northern China’s agro-pastoral zone,which are divided into three cites of different grazing intensities:light(6 sheep/hm²),medium(10 sheep/hm²),and heavy(13 sheep/hm²).The result shows that different grazing intensities tend to affect the soil microbial biomass of carbon and nitrogen in similar ways. During the grazing period,the soil microbial biomass of the two elements is higher in pastures of medium grazing intensity,while during the rest-grazing period,they are higher in pastures of light grazing intensity and in the control sites.Following the prolonged grazing and deterioration of the environment,the pasture soil micro-biomass carbon and nitrogen decrease incessantly.Judging from the worsening situation,we suggest the grazing-intensity limit in an arid area should be restricted at 6 sheep per square hectometer.

Key words: Grazing intensity, Pasture, Microbial biomass-carbon, Microbial biomass-nitrogen

摘要： 试验测定了华北农牧交错带地区不同放牧强度下(轻牧,6只羊/hm²;中牧,10只/hm²;重牧,13只/hm²)人工草地土壤微生物量碳、氮含量的变化。结果表明:在不同放牧强度下,微生物量碳氮有相似的变化趋势,放牧期间均以中牧区较高,在停牧年,以轻牧区和对照区较高;随着放牧时间延长及环境条件恶化,土壤微生物量碳氮含量随放牧强度增加而迅速降低;从微生物量碳氮随放牧强度变化的角度,在干旱地区放牧强度不宜高于轻牧。

关键词: 放牧强度, 草地, 微生物量碳, 微生物量氮