中文摘要：

有关黄土高原历史时期原生植被类型的研究不仅具有重要的理论意义，也具有现实的指导意义。土壤有机质稳定碳同位素（δ^13Corg）是区域植被中C4／C3植物相对丰度的灵敏指示器，对黄土有机质稳定碳同位素的研究可以部分地重建过去的植被类型变化历史，并可探讨与此有关的气候、环境问题。已有的研究结果表明：黄土高原古土壤发育阶段δ^13Corg偏正于黄土沉积阶段，表明随气候由冷干向暖湿转变黄土高原C4植物相对丰度上升，然而在C4植物相对丰度上升的主要驱动因素上仍存在夏季风和温度两种观点。相应的在空间上，C4植物的相对丰度无论冰期还是间冰期都是由黄土高原东南向西北递减。而基于黄土δ^13Corg的研究认为黄土高原历史时期一直以草原为主，不存在大面积的森林。尽管已有的研究对黄土有机质稳定碳同位素分布和变化的一般性规律取得了共识，但在研究中还存在一些问题，在黄土δ^13Corg变化机制上还存在争议，值得进一步研究。

英文摘要：

Soil stable organic carbon isotopic composition （δ^13Corg） is a sensitive indicator of relative abundance of local C4/C3 plants due to the distinct distribution range of their δ^13Corg and has little or no isotopic fractionation during bury and decompound process of plants. Chinese Loess Plateau （ CLP）, located in the northwest inner continent, is a sensitive area to climatic and environmental change and weak change of climate and environment can result in strong landscape change. So, the research on δ^13Corg of Chinese loess can partly reconstruct paleovegetation type, and furthermore, indicate the relationships between climate and environment related to paleovegetation. Reviews on δ^13Corg studies of Chinese loess showed： δ^13Corg of Chinese loess more positive in paleosols developed during warm and moist interglacials and more positive southeastward in both paleosols and loess. The available δ^13Corg data indicate the proportion of C4 plants increasing form glacial to interglacial and from the northwestern part to southeastern part of CLP. The past vegetation type of CLP determined as grassland still lack direct evidences because of all trees are also use C3photosynthesis pathway. The key control environmental factors on C4 plants, such as temperature and Asian Summer Monsoon are still debated. Although the general rule of the distribution of Chinese loess δ^13Corg is clear in both temporal and spatial sequence, some other problems including the control mecha- nism on Chinese loess δ^13Corg are still blurry. Further understanding of Chinese loess δ^13Corg needs more research work.