Spatial Distribution of Stable Carbon Isotope Compositions of Plant Leaves in the North of the Tibetan Plateau

Tibetan Plateau is an important position for studying the global changes due to its ecological vulnerability and climatic sensitivity. The stable carbon isotope compositions in plant leaves can be used to provide information of original carbon in soil organic matter and paleo-ecological evolutions, based on the good relationship between the stable carbon isotope compositions and water use efficiency in plants or plant productivity to some extent. However, the pattern of spatial distribution of stable carbon isotope compositions of plant leaves in the Tibetan Plateau is less studied. The aim of this study is to determine the effects of altitude, latitude and longitude on foliar δ 13C values and their mechanisms.;A total of 101 samples used in this study were collected from 13 sites in the northern part of the plateau. The analyses show that foliar δ 13C, with an average of {-26.89‰}, ranged from {-29.52‰} to {-23.85‰}. The δ 13C increased with increasing altitude and decreasing latitude and longitude. There was a statistically insignificant effect of soil water contents and soil temperature on the foliar δ 13C. These results suggest that altitude effect of foliar δ 13C was mainly ascribed to temperature and atmospheric pressure (the partial pressure of CO 2), while temperature and relative humidity were possibly responsible for the latitude and longitude trends of foliar δ 13C.