Correlations between foliar stable carbon isotope composition and environmental factors in desert plant Reaumuria soongorica (Pall.) Maxim.

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 delta C-13 values and environmental factors. Results showed that delta C-13 values in R. soongorica ranged from -22.77%o to -29.85% and that the mean delta C-13 value (-26.52%) was higher than a previously reported delta C-13 value for a different desert ecosystem. This indicates that R. soongorica belongs to the C-3 photosynthetic pathway and has higher water use efficiency than other species. The correlations between delta C-13 values and environmental factors demonstrated that the foliar delta C-13 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 delta C-13 values in R. soongorica was not obvious and there was no significant correlation between the delta C-13 values and mean annual temperature. We conclude that different distribution trends in delta C-13 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 delta C-13 values for R. soongorica reinforced that it is a super-xerophil in terms of its adaptive strategies to a desert environment.