| This paper presented a comprehensive investigation on ecophysiological characteristics of halophytes in Ebinur Lake Wetland Nature Reserve with the application of stable carbon isotope technique. The stable carbon isotope ratios (δ13C) were measured in leaves of 29 halophytes and 6 non-halophytes. At the same time, the physiological factors of all these species including leaf water content, soluble protein, proline, soluble sugar, nitrate nitrogen and nitratase activity, and the physical and chemical properties of soil such as water content, soluble salt, pH were analyzed. The distribution characteristics of stable carbon isotope of different halophytes leaves and the correlations betweenδ13C values and the environmental factors and physiological factors were analyzed and to discuss water use efficiency (WUE) of Halophytes in the area and the physiological adaptive mechanism. The results showed that:1. Theδ13C values of 35 species were measured and had an extensive range from -16.63‰to -29.59‰. Among 31 C3 species, theδ13C values of non-halophytes ranged from -27.06‰to-29.51‰and the averageδ13C value was -28.43‰; theδ13C values of halophytes ranged from -26.00‰to -29.59‰and the averageδ13C value was -27.85‰, which is more positive than the averageδ13C value of non-halophytes. Theδ13C values of four C4 species ranged from -16.63‰to -17.39‰, which belong to the Chenopodiaceae, the averageδ13C value was -16.88‰. From the distribution of the C4 species, we can see that the Chenopodiaceae had strong ability to adapt to drought and had an extremely important position in the flora of the region.2. Theδ13C values was negatively correlated with leaf water content, and no significantly correlated with soluble protein, praline, and soluble sugar in leaves of different C3 species, which indicated that plant with lower leaf water content had higher water use efficiency, and even showup more conserved pattern of water use efficiency possibly.Leaf water content was also negatively correlated with soluble sugar. Through comparing with different sites indicated that the available soil moisture had greater impact on theδ13C values of plants; Average proline content of plants in drought habitats was 24.4μg.g-1FW higher than that in moist habitats; the leaf water content had no distinct difference in different sites, which indicated that plants can possibly accumulate a high-level of praline content and other substances to enhance the capacity of osmotic adjustment and keep relatively stable leaf water content to maintain the physiological metabolism normally.3. Among C3 halophytes, Shrubs/semi-shrubs had the highest water use efficiency, perennial herbs were the second, arbors and annual herbs were the lowest. It shows that Shrubs/semi-shrubs more adapted to drought and salt habitat; Perennial herbs had higher water use efficiency than annual herbs and higher competitive advantage. Judged from osmotic regulation material, shrubs/semi-shrubs and perennial herbs had more strong drought resistance.4. Theδ13C values of C3 Halophytes were 0.88‰higher than non-halophytes approximately, which indicated that the higher water use efficiency of halophytes. Three types of halophytes (euhalophyte, recretohalophyte and pseudohalophyte) were no significant difference in water use efficiency. The difference of osmotic adjustment material indicated that there were different adaptation strategies to adapt adversity of drought and salinity. Tamaricaceae had the highest water use efficiency, Chenopodiaceae and Leguminosae were the second and Apocynaceae was the lowest; with the highest nitratase activity may indicate that Apocynaceae had a higher utilization rate of nitrogen.5. Typical C4 plant-Haloxylon ammodendron and typical C3 plant-Populus euphratica, whichδ13C values of leaves in June were higher than August; theδ13C values of different halophytes in June are different in August. Theδ13C values of eight species in June were significantly higher than August. Various plants in different seasons were with different water use efficiency, but the general tendency was that the water use efficiency in the early growth stage is higher than later.
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