Key messageThe responses of tree leaf delta C-13 to climatic and geographic factors were different among major climate zones in China, suggesting that the environmental influences on tree ecophysiology are different among climates. Leaf stable carbon isotope composition (delta C-13) integrates information about environmental effects on plant carbon and water balance. However, extensive inconsistent findings have been reported regarding the variability of leaf delta C-13 along environmental gradients, impeding the interpretations of plant physiological responses to environmental changes using delta C-13 values. In this study, data from 505 tree leaf delta C-13 measurements and climatic and geographic information at 186 sites across China were collected from peer-reviewed articles. The dataset was grouped according to the Koppen-Geiger climate classification for investigating the variations in tree leaf delta C-13 with climatic and geographic factors among different climate zones. Multiple regression analyses were conducted using this dataset to provide a predictive model for tree leaf delta C-13 variability in China. The results showed that the tree leaf delta C-13 was - 28.05(sic) on average and was highest in the polar climate (- 26.82(sic)), lowest in the warm temperate climate (- 29.66(sic), and almost the same in the temperate arid (- 27.60(sic) and cold temperate (- 27.69(sic)) climate zones. We found that the magnitude of the leaf delta C-13 values of certain climates was partly determined by the functional type of local tree species. Moreover, the relationship between tree leaf delta C-13 and mean annual precipitation (MAP) was found to be significantly positive only for the temperate arid climate zone, while significant negative correlations were found for the other climate zones. Tree leaf delta C-13 was significantly negatively related to mean annual temperature (MAT) in the warm temperate and polar climate zones, and it was positively related to altitude in the warm temperate and cold temperate climate zones. These results suggest that the widely observed inconsistent responses of leaf delta C-13 to environmental factors, as well as the inconsistent delta C-13 values of a specific tree functional type, can be attributed to the climate conditions in which the tree inhabits. Finally, a simple regression model incorporating MAT, MAP, and altitude was proposed, which explained 45% of the variation in tree leaf delta C-13. These findings could be useful in evaluating potential changes in tree physiological traits under the changing climate in China.