Abstract: Understanding the response of plant element concentrations and stoichiometry to the changes of soil factors is essential to predict the responses of fragile and sensitive ecosystems to environmental changes. We examined the ecological stoichiometry of different organs in Phragmites australis and the driving factors in a wetland of Yangguan, Dunhuang. The results showed that carbon (C) and phosphorus (P) concentrations in different organs of P. australiswere in a descending order of leaf > root > stem, nitrogen (N) concentration and N∶P were in order of leaf > stem > root, C∶N was in order of root > stem > leaf, and C∶P was in order of stem > root > leaf. The concentration of C in leaves and roots was significantly higher than that in stems (P<0.05), but there was no difference between leaves and roots (P>0.05). The concentrations of N, P and C∶N, C∶P and N∶P varied among organs (P<0.05). Root N∶P of P. australis was <14, leaf N∶P was >16, and stem N∶P was between 14 and 16. The C concentrations of different organs were not significantly correlated (P>0.05). The N concentrations between root and stem and that between root and leaf showed a significantly positive correlation (P<0.01). The P concentrations between root and stem were positively correlated (P<0.01). There was a positive correlation between soil salinity and N concentration in roots and stems (P<0.01). The P concentrations in stems and leaves were significantly positively correlated (P<0.05). Soil P concentration was positively correlated with stem P concentration (P<0.01). Soil available P concentration was positively correlated with root and stem N concentration (P<0.05). Soil P was the main factor driving the stoichiometry of roots and stems of P. australis, while soil salinity was the main factor driving the stoichiometry of leaves. P. australis tended to adapt to the high salinity and low P conditions by increasing the N concentration in various organs.

Key words: wetland in arid area, Phragmites australis organ, stoichiometry, soil factor.