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In order to investigate the distribution characteristics of stable carbon isotope ratios (δ13C) in the desert plant Reaumuria soongorica, the δ13C values of leaves were measured in 407 individuals of 21 populations. Soil physicochemical properties including soil water content, soil total dissolved solids, soil total nitrogen, soil total phosphorus and soil organic content were also analyzed in order to survey the major factors influencing δ13C values on spatial variation. Leaves and soil samples were simultaneously collected from the ten major distribution areas in Northwest China at altitudes from 394 m to 1 987 m above sea level, at latitudes from 36°10′N to 44°33′N, and at longitudes from 81°43′E to 106°37′E. These ten areas include Shihezi, Baicheng, Yiwu areas in Xinjiang Uygur Autonomous Region; Anxi, Zhangye, Baiyin, Lanzhou areas in Gansu Province; Shapotou, Yinchuan areas in Ningxia Hui Autonomous Region; and Alashan County in Inner Mongolia Autonomous Region. The results show that the δ13C value of R. soongorica ranges from ?22.77‰ to ?29.85‰ with an average of ?26.52‰. Foliar δ13C values in R. soongorica are not significantly correlated with altitude, latitude or longitude, and a spatial distribution trend of δ13C values of R. soongorica is not obvious on a large scale. However, when δ13C values of two R. soongorica populations under the same climate conditions are compared, δ13C values increase obviously from east to west and from north to south. As none of the soil total dissolved solids, soil total nitrogen, soil total phosphorus, and soil organic content shows a uniform trend from east to west and from north to south, we suppose that the small-scaled spatial distribution pattern of δ13C values of R. soongorica is mainly controlled by the soil water content. |
