中文摘要：

C／N比值在湖泊沉积物研究中广泛用于反映有机质的来源；在冰缘冻土区、热带和地中海地区主要用于指示有机质的分解程度。然而，有关C／N比值在中国黄土沉积中指示意义的研究目前讨论的较少。选取位于干旱一半干旱区的黄土高原中部西峰和洛川竖井剖面为研究对象，对该区末次间冰期以来土壤有机碳及全氮的时间分布规律进行了初步研究，结果表明研究剖面磁化率、T0c和TN含量及C／N比值的垂直分布趋势一致，古土壤层的TOC和TN含量及C／N比值相对黄土层偏高，而TN含量值在整个序列均在0．03％～O．05％的低值范围，波动很小。因此，初步认为c／N比值在中国黄土高原地区主要响应上覆植被TOC输入的多少，即C／N比值在干旱半干旱的黄土沉积序列更多地指示上覆植物生物量的大小。

英文摘要：

C/N ratio is extensively used to reflect the sources of the organic matter in the lake sediments. In some districts, such as frozen soil distriets, the tropical zone and Mediterranean area, it indicates the degree of soil organic matter （SOM） degradation. However, there are few discussions about the implica- tion of C/N ratio in Chinese loess sediments until now. Therefore, we chose two phreatic profiles in Xifeng and Luochuan from the central Chinese Loess Plateau in arid semiarid area, and obtained the temporal dis- tribution of soil organic carbon and total nitrogen content since the last interglacial. The result shows that, the downcore distributions of magnetic susceptibility, TOC and TN content, and C/N ratio exhibit the similar trends with higher value in paleosol and lower in loess. Besides that, TN content is in the low range of 0. 03~0. 05% in the whole sequence. So, we preliminarily suggest that C/N ratio mainly re- spond to the input amount of the organie matter from the above coverage. Accordingly, C/N ratio is more likely to indicate the relative production of the above eoverage in temperate arid-semiarid loess sediments.