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Understanding the stable carbon isotopic composition (delta C-13) of surface soil organic matter under various climates is crucial for quantitative reconstruction of past climatic changes. Although the relationship between precipitation and plant delta C-13 is well understood at global and regional scale, studies relating delta C-13 of surface soil organic matter to precipitation in northern China remain controversial. In this study, 90 surface soil samples were collected from the desert/loess transition zone of Northern China, where vegetation is sensitive to climatic changes. The stable carbon isotopic composition of organic matter in these soil samples was analyzed in order to examine its palaeoclimatic implications. Our results show that the delta C-13 varied from -26.56 to -19.41% among the investigated sites, with an average of -23.54%. There was a strong negative correlation between the delta C-13 of surface soils and the mean annual precipitation (MAP) (R-2 - 0.52, p < 0.05). Variation in the delta C-13 of C-3 plants was the main factor that determined the delta C-13 of soil organic matter. The C-4/C-3 biomass ratio may also contribute to the delta C-13 changes, but this effect was relatively minor in our study area. Our findings suggest that a general transform function between the proxy index delta C-13 value and climates may not be applicable at one specific site, and that a comprehensive investigation is needed when reconstructing the past climate change using the delta C-13 of buried soils. (C) 2014 Elsevier Ltd and INQUA. All rights reserved.