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Nitrogen cycling is tightly associated with environment. The south slope of a given mountain could significantly differ from north slope in environment. Thus, N cycling should also be different between the two slopes. Since leaf delta N-15, soil delta N-15 and Delta delta N-15(leaf-soil) (Delta delta N-15(leaf-soil) D leaf delta N-15 soil delta N-15) could reflect the N cycling characteristics, we put forward a hypothesis that leaf delta N-15, soil delta N-15 and Delta delta N-15(leaf-soil) should differ between the two slopes. However, such a comparative study between two slopes has never been conducted. In addition, environmental effects on leaf and soil delta N-15 derived from studies at global scale were often found to be different from those on a regional scale. This led to our argument that environmental effects on leaf and soil delta N-15 could depend on local environment. To confirm our hypothesis and argument, we measured leaf and soil delta N-15 on the south and north slopes of Tian Shan. Remarkable environmental differences between the two slopes provided an ideal opportunity for our test. The study showed that leaf delta N-15, soil delta N-15 and delta N-15(leaf-soil) on the south slope were greater than those on the north slope, although the difference in soil delta N-15 was not significant. The result confirmed our hypothesis and suggested that the south slope has higher soil N transformation rates and soil N availability than the north slope. In addition, in this study it was observed that the significant influential factors of leaf delta N-15 were temperature, precipitation, leaf N, leaf C = N, soil moisture and silt = clay ratio on the north slope, whereas on the south slope only leaf C = N was related to leaf delta N-15. The significant influential factors of soil delta N-15 were temperature, precipitation, soil moisture and silt = clay ratio on the north slope, whereas on the south slope, mean annual precipitation and soil moisture exerted significant effects. Precipitation exerted contrary effects on soil delta N-15 between the two slopes. Thus, this study supported our argument that the relationships between leaf and soil delta N-15 and environmental factors are localized.