Abstract: Leaves of 407 individuals of Reaumuria soongorica (Pall.) Maxim. collected from the major distribution areas were measured to investigate the distribution characteristics of the stable carbon isotope in this desert plant, as well as correlations between 13C values and environmental factors. Results showed that 13C values in R. soongorica ranged from –22.77‰ to –29.85‰ and that the mean 13C value (–26.52‰) was higher than a previously reported 13C value for a different desert ecosystem. This indicates that R. soongorica belongs to the C3 photosynthetic pathway and has higher water use efficiency than other species. The correlations between 13C values and environmental factors demonstrated that the foliar 13C values in R. soongorica increased significantly with decreasing mean annual precipitation and mean relative humidity, and decreased with decreasing duration of sunshine and evaporation. The spatial distribution trend of 13C values in R. soongorica was not obvious and there was no significant correlation between the 13C values and mean annual temperature. We conclude that different distribution trends in 13C values for R. soongorica were likely caused by stomatal limitation rather than by nutrient-related changes in photosynthetic efficiency and that precipitation played an important role in the wide distribution range of R. soongorica. This pattern of 13C values for R. soongorica reinforced that it is a super-xerophil in terms of its adaptive strategies to a desert environment.

Key words: carbon isotope composition, desert plant, meteorological factor, Reaumuria soongorica.