中文摘要：

研究现代地表沉积物有机碳同位素与植被-气候的关系，对于重建过去气候变化过程有重要意义。然而，对于气候变化幅度大、生态环境脆弱的浑善达克沙地，尚缺少相关的研究。本研究对浑善达克沙地进行了全面采样。对42个地表样品进行了有机碳同位素分析。结果表明，浑善达克沙地表土有机碳同位素（δ^13C）介于-25．0％o-19．4‰之间，平均为-22．2‰。通过两端元方法估算，研究区C4生物量介于0～46％之间，平均为17．9％，与前人的C4植被调查结果有很好的可比性。相关分析表明，C4生物量与年降水量呈显著负相关关系，而与温度关系不大，这表明在该地区年均温差异较小的情况下，降水可能是控制C4植物生物量的主要因素；另外，推测也可能是研究区C3生物量的变化主导地表有机碳同位素的变化。建立的δ^13C-年降水量转换函数，预期可用于重建浑善达克沙地全新世降水量的变化。

英文摘要：

composition of surface soil and vegetation-climate is fundamental for reconstruction of past climate change. However,lacking of this kind of study in Otindag dune field, has hindered our understanding of the past environmental changes in this monsoon sensitive region. δ^13C of organic matter could be among the most powerful proxy for reconstructing past vegetation and climate. This study aims to develop the relationship betweenδ^13C and climate factors. We systematically sampled the surface sediments in Otindag dune field,total 42 samples were collected to a depth of approximately 5cm for organic carbon isotope analysis in the field. After pretreatment in laboratory, samples were measured by Thermo Finnigan MAT DELTAp~u~ XP mass spectrometer, with a precision better than 0.4%o. Climate data of meteorological stations was collected and spatial interpolations were accomplished using ArcGIS package,and climate factors（MAT and MAP） of each sampling site were extracted. Combine with obtained vegetation type data in each sampling site, quantitative relationship between soil organic carbon isotope and climate factors can be reconstructed. The results show that δ^13C value of the surface sediments in the Otindag dune field is between -25.0‰ and -19.4%0, with an average of-22.2‰. On the basis of the two-member mixing model,the C4 plants account for 0- 46% biomass with an average of 17.9% in this dune field, which was consistent with modern vegetation investigation study. In addition,the analysis also shows that there is a significant correlation （R2= 0. 5821, n =42, p〈0. 001 ） between the C4 biomass and the annual precipitation,while no clear relationship between the C4 biomass and the annual temperature（R2 =0. 0285） ,indicating that the annual precipitation is a major factor controlling the C4 biomass,while the temperature has little influence on C4 plants. Finally, an empirical equation was established between the 613C value and the annual precipitation in the Otindag dune field（y=-0. 0137x-18.