中文摘要：

应用稳定性碳同位素（δ13C）技术分析了放牧对内蒙古短花针茅荒漠草原主要植物和土壤的δ13C值的影响。研究结果显示：重度放牧干扰显著降低了主要6种C3植物的δ13C值，增加了C4植物木地肤的δ13C值，而对c4植物无芒隐子草的δ13C值影响不显著。可以看出放牧对不同光合类型植物的δ13C值影响是不一样的。同时，长期重度放牧显著地增大了0—15cm深度内土壤的δ13C值，尤其表层土壤（0-5cm）的变化幅度较大，说明放牧对表层土壤有机质的分解影响程度更大一些。

英文摘要：

Effects of grazing on δ13C values of plants and soils were investigated by applying the stable carbon isotope techniques in a Stipa breviflora desert steppe in Inner Mongolia. The results showed that long--term heavy grazing significantly decreased the δ13C values of 6 species of C3 plant and increased theδ13C value of Kochia prostrate, whereas did not affect the δ13C values of Cleistogenes songorica, which indicated that effects of grazing on different types of photosynthetic pathway plants were different. The δ13Cvalues of soils（0-15cm） were in the grazed area was significantly higher than that in un--grazed area, especially in 0-5cm layer, which showed that grazing could greatly affect the organic matter decomposition of the soil surface.