Evaluating the response of <i>δ</i><sup>13</sup>C in <i>Haloxylon ammodendron</i>, a dominant C<sub>4</sub> species in Asian desert ecosystems, to water and nitrogen addition as well as the availability of its <i>δ</i><sup>13</sup>C as an indicator of water use efficiency

Abstract. Variations in precipitation and atmospheric N deposition affect water availability desert thus may have significant effects on ecosystems. Haloxylon ammodendron is a dominant plant Asian desert, addressing its physiological acclimatization to the changes can provide insight into how plants adapt extreme environments by adjustment. Carbon isotope ratio (δ13C) has been suggested as sensitive long-term indicator of acclimatization. Therefore, this study evaluated effect change increasing δ13C H. ammodendron. Furthermore, C4 plant; whether indicate use efficiency (WUE) not addressed. In present study, we designed field experiment with completely randomized factorial combination measured gas exchange Then calculated degree bundle-sheath leakiness (φ) WUE assimilating branches φ remained stable under supply, while addition, addition their interaction affected had no correlation WUE. These results were associated irrelevance between intercellular ambient CO2 concentration (ci / ca), which might be caused special value (0.37) or lower activity carbonic anhydrase (CA) conclusion, global cannot used for indicating