Soil n ‐alkane δ 13 C along a mountain slope as an integrator of altitude effect on plant species δ 13 C

Carbon isotopic compositions of leaf wax‐derived n ‐alkanes ( δ 13 C wax ) and bulk organic matter ( δ 13 C SOM ) 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 δ 13 C wax and δ 13 C SOM trends. Above the threshold, δ 13 C wax and δ 13 C SOM 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 δ 13 C response to precipitation at water‐limited areas. Because δ 13 C wax and δ 13 C SOM naturally integrate plant species and time, this work demonstrates that the altitude‐induced environmental impact on plant species‐level δ 13 C has been conveyed to soils, and that the species‐level δ 13 C could be linearly scaled up to the community level.