Abstract: Along with the intensification of global change, more and more researches have been focused on the ecological effects of nitrogen deposition, especially for the deserts which are limited by nitrogen availability and sensitive to changes in nitrogen inputs. Moss crust is the late successional stage of biological soil crusts, which plays an important role in nitrogen cycling of deserts. However, the responses of moss nutrient to nitrogen deposition are still unclear. In this study, different nitrogen deposition levels (0-3 g N·m^-2·a^-1) were simulated on moss crust dominated by S. caninervisin the Gurbantunggut Desert. Nitrogen and phosphorus stoichiometry in aboveground and belowground parts of S. caninervis under nitrogen deposition were examined. Concentrations of nitrogen (17.89 g·kg^-1) and phosphorus (1.81 g·kg^-1) in the aboveground part of moss were higher than that in the belowground part (13.95 vs. 1.28 g·kg^-1), while there was no difference in ratio of nitrogen to phosphorus between the two parts. With increasing nitrogen deposition level, the concentrations of nitrogen and phosphorus in the aboveground part increased firstly and then decreased. The nitrogen concentration in the belowground part had a similar trend to that in the aboveground part, whereas the phosphorus concentration was not affected by nitrogen addition. The ratio of nitrogen to phosphorus in aboveground part remained relatively stable, while the ratio in belowground part increased with increasing nitrogen deposition level. Our results showed that the stoichiometric response of S. caninervis was consistent with its growth responses, with positive effects of low nitrogen addition dose and negative effects of high dose.Nitrogen and phosphorus concentrations can vary coordinately between the aboveground and belowground parts and showed an allometric relationship. This study improved our understanding of the adaptive ability of desert mosses, and provided scientific basis to assess the growth trend of desert mosses under long-term nitrogen deposition.

Key words: nitrogen deposition, Syntrichia caninervis, stoichiometry, allometric growth, Gurban tunggut Desert.