Variation in foliar stable carbon isotope among populations of a desert plant, Reaumuria soongorica (Pall.) Maxim. in different environments

The stable carbon isotope ratios of the desert plant Reaumuria soongorica and the physicochemical properties of soil were analyzed in order to investigate the distribution characteristics of δ13C values in this desert plant, and to examine the correlations between δ13C values and the soil factors in the major distribution areas in northwestern China. Leaves were collected from the natural distribution areas, at the mean annual precipitation (ranging from 27 to 328 mm), at altitudes from 394 to 1987 m above sea level, at latitudes from 36°N to 45°N and at longitudes from 81°E to 107°E. The correlations between δ13C values and the soil factors demonstrated that the foliar δ13C values in R. soongorica significantly increased with decreasing soil water content (SWC) and increasing total dissolved solids (TDS) in soil. There were no significant correlations between the δ13C values and pH, total nitrogen, soil organic matter (SOM), total phosphorus and effective phosphorus in soil. The results showed that the main soil factors affecting δ13C values in the desert halophyte R. soongorica were SWC and TDS. The mean δ13C value in R. soongorica was higher than previously reported δ13C values in different desert ecosystems. We concluded that the variation in δ13C values of R. soongorica was probably caused by stomatal limitation rather than by nutrient-related changes in photosynthetic efficiency. This pattern of δ13C values in R. soongorica reinforced that it is a super-halophyte in terms of adaptive strategies to arid environments.