Spatial patterns of leaf δC and δN of aquatic macrophytes in the arid zone of northwestern China.

Analysis of stable isotope composition is an important tool in research on plant physiological ecology. However, large-scale patterns of leaf-stable isotopes for aquatic macrophytes have received considerably less attention. In this study, we examined the spatial pattern of stable isotopes of carbon (δC) and nitrogen (δN) of macrophytes leaves collected across the arid zone of northwestern China (approximately 2.4 × 10 km) and attempted to illustrate its relationship with environmental factors (i.e., temperature, precipitation, potential evapotranspiration, sediment total carbon and nitrogen). Our results showed that the mean values of the leaf δC and δN in the macrophytes sampled from the arid zone were -24.49‰ and 6.82‰, respectively, which were far less depleted than those measured of terrestrial plants. The order of averaged leaf δC from different life forms was as follows: submerged > floating-leaved > emergent. Additionally, our studies indicated that the values of foliar δC values of all the aquatic macrophytes were only negatively associated with precipitation, but the foliar δN values were mainly associated with temperature, precipitation, and potential evapotranspiration. Therefore, we speculated that water-relation factors are the leaf δC determinant of macrophytes in the arid zone of northwestern China, and the main factors affecting leaf δN values are the complex combination of water and energy factors.