The Tibetan plateau is an important place for global changes studies owing to its ecological fragility and climatic sensitivity. The stable carbon isotope compositions in plant leaves can be used to provide information on the origin of carbon in soil organic matter and paleo-ecological evolutions due to the good relationship between the stable carbon isotope compositions and water use efficiency in plants or plant productivity to some extent. However, the knowledge about the pattern of spatial distribution of stable carbon isotope compositions of plant leaves in the Tibetan plateau is less available.
A total of 101 samples used in this study was collected from 13 sites in the northern part of the Tibetan plateau. The analyzed results show that foliar δ13C values in the northern Tibet , with an average of -26．89‰, were higher than other mountain regions in the world. Interestingly, C4 plants were found at the elevation of 4 161 m, where there was usually no C4 species distribution. The foliar δ13C values increased with increasing altitude, however, the amplitude of increase was dependent on species. Furthermore, compared with plants grown in the northern part of Tanggula mountains, there were significantly higher δ13C values at the southern part. The analysis revealed that the differences of δ13C values between the northern and southern part of Tanggula mountains were mainly ascribed to precipitation.