Carbon isotopic compositions of leaf wax-derived n-alkanes (δ13Cwax) and bulk organic matter (δ13CSOM) in surface soils from ca. 1000 to 3800 m above sea level along Mount Gongga, China were investigated for their altitudinal variations. There is a breakpoint, suggesting a precipitation threshold, at 2050 m in both δ13Cwax and δ13CSOM trends. Above the threshold, δ13Cwax and δ13CSOM increase in a similar pattern of the average species-level response to altitude reported from various humid mountainous areas. However, a significant decreasing trend with altitude occurs below the threshold, within which climate changes upward from arid to humid, consistent with plant foliar δ13C response to precipitation at water-limited areas. Because δ13Cwax and δ13CSOM naturally integrate plant species and time, this work demonstrates that the altitude-induced environmental impact on plant species-level δ13C has been conveyed to soils, and that the species-level δ13C could be linearly scaled up to the community level.