ALTITUDINAL TRENDS IN STABLE CARBON ISOTOPE COMPOSITION FOR POECEAE ON QINGHAI-TIBETAN PLATEAU

In a global survey of d ¹³C values of plants collected from a wide range of altitudes, spanning many taxonomic and physiognomic groups as well as a wide geographic range. Korner et al. found that the d ¹³C values increased with altitude. Other researchers found that the d ¹³C values in single species increase with altitude. However, Most of these studies were carried out on a very restricted range of sites. So far, relatively few systematic studies have addressed how the d ¹³C values in single species growing in a complicated environment like Qinghai-Tibetan Plateau change with altitude.

This time, the stable carbon isotope compositions are determined on leaves of Poaceae plants (Trisetum spicatum, Roegneria nutans, Stipa purpuarea, Elymus nutans) sampled along a 2000-km transect on Qinghai-Tibetan Plateau of China. The d ¹³C values for all samples increase with altitudes generally, the mean d ¹³C increase with altitude is 1.37°ë /km. Carbon isotope ratios of Trisetum spicatum and Roegneria nutans increase significantly with altitudes. The result of linear analyses indicates that the temperature and the CO₂ partial pressure are the major factors causing the d ¹³C ratios of C₃ plants to increase with altitudes. In this study, we find C₄ plants: Chloris virgata£¬Eragrostis ferruginea, Eragrostis nigra, Arundinella yunnanensis, Orinus thoroldii, Pennisetum centrasiaticum, some of them distributed above 4000m, even reached 4520m.