Abstract: Effects of stocking rates on C, N, P contents and distributions in Plant-soil system in Leymus chinensis steppe, Inner Mongolia. There are four treatments in the control experiment:1.33sheep/hm²,4 sheep/hm²,6.67 sheep/hm² and a ungrazed Plot. The results indicated that plan species,aboveground and underground biomass, chemical composition in Plant and soil have changed greatly after 8grazing years. The aboveground and underground biomass in 0~60cm are significantly higher than those in grazing treatments, but not significantly different among the grazing treatments. Plant carbon content was higher under control and 1.33 sheeo/hm² than those under 4 and 6.67 sheep/hm², but N, P content, vice versa. C/N and C/P ratio in plant were smallest in 4 sheep/hm² treatment. It had showed significant surfication of root and nitrogen content in root under 6.67 sheep/hm² treatment. Soil C in 0~10cm depth under control treatment was higher than those of other three grazing treatments. No significantdifference of soil C in 0~10cm soil layer was observed among three grazing treatments. Soil organic carbon and nitrogen contents were significantly positive to root biomass.Inorganic N in 0~10cm soil was highest in 4 sheep/hm². Soil microbial C and P in 0~10cm depth were significantly reduced only under6. 67 sheep/hm². Soil microbial biomass N was higher under 4 and 6.67 sheep/hm².

Key words: Stocking rate, Plan-soil system, C, N, P contents, Leymus chinensis steppe

摘要： 本文研究不同放牧率对草原植物土灌系统中C、N、P含量的影响。结果表明,对照区地上生物量和0～60m土层的总根量显著大于各放牧处理(P＜0.01),而放牧处理间差异不显著(P＞0.05)。对照区和1.33只羊/hm²处理植物的C含量显著大于4只羊/hm²和6.67只羊/hm²,而后两个处理的N、P含量较高。4只羊/hm²处理的C/N和C/P最小。6.67只羊/hm²处理已使根系和根系中的N素明显向表层聚集。对照区0～10cm土层土壤有机C含量显著大于各放牧处理,而各放牧处理间差异则不显著。土壤有机C,N含量与报系生物量成显著正相关。0～10cm土层中无机N在4只羊/hm²处理中最大。土壤微生物量C、P含量在6.67只羊/hm²处理中显著降低,其它处理间差异不显著。其中4只羊和6.67只羊/hm²处理的微生物N含量较高。

关键词: 放牧率, 土壤-植物系统, C、N、P含量, 羊草小禾草草原