Relationships between altitudinal gradient and plant carbon isotope composition of grassland communities on the Qinghai-Tibet Plateau, China

Foliar and root carbon isotope composition (delta C-13) of grassland communities on the Qinghai-Tibet Plateau, China, was obtained by the biomass weighting method and direct measurement. We investigated the characteristics and altitudinal patterns of foliar and root delta C-13 and determined which environmental factors influenced foliar delta C-13 most. Foliar delta C-13 of alpine steppe was significantly higher than that of alpine meadow and temperate steppe. For alpine meadow, root delta C-13 was significantly higher than of foliar delta C-13. Foliar delta C-13 increased with altitude at an average rate of 0.60aEuro degrees km(-1) for the whole grassland ecosystem. This rate was lower than that at species level. However, there were no significant relationships between root delta C-13 and altitude. Atmospheric pressure was a more important factor than temperature and precipitation in its influence on the altitudinal pattern of foliar delta C-13 at the community level.