The Pattern of Stable Carbon Isotope Ratios in \%Sabina przewalskii\%

C values in different organs are different. Tree leaves have the lowest, while tree trunks have the highest δ~ 13C value. δ~ 13C also varies with exposure, with a relatively lowest δ~ 13C value in the north. There is an inconsistent trend existing in wood δ~ 13C values of different height along the trunk, suggesting no carbon isotope discrimination during the period of the downward transportation of leaf's organic compounds. Irrespective of tree height and exposure, wood δ~ 13C values have become lower and lower for the past 60 years.