Reaumuria soongorica is an important biological barrier for ecological protection in the Gobi Desert in northwestern China, where soil nitrogen availability is low. N deposition has recently increased significantly in Gobi Desert, and the responses of R. soongorica to N enrichment may become a problem for ecological restoration and protection. However, little is known about the effects of N addition on the biomass, non-structural carbohydrates (NSC), and carbon:nitrogen:phosphorus (C:N:P) stoichiometry of R. soongorica in this region. Here, we examined changes in biomass, NSC and C:N:P ratios of different organs of R. soongorica seedlings in four N addition treatments: 0 (N0), 4.6 (N1), 9.2 (N2), and 13.8 (N3) g m−2 year−1. N addition up to 9.2 g m−2 year−1 significantly increased the biomass of different organs, simultaneously increasing the belowground: aboveground ratio of R. soongorica seedlings. Root NSC concentrations significantly increased under all N addition treatments, but leaf and stem NSC concentrations only increased under the N1 and N2 addition treatments. Nitrogen addition enhanced the soluble sugar concentrations (SSC) of leaves and roots, and reduced starch concentrations (SC) of all organs. Stem and root N concentrations significantly increased under the N2 and N3 treatments, and leaf N concentrations only increased under the N3 treatment, but N addition had no significant effect on plant C and P concentrations. Leaf and stem C:N ratios decreased significantly under the N2 and N3 treatments, but root C:N decreased significantly in all N addition treatments. The N3 treatment significantly increased the N:P ratio of all organs. N addition significantly enhanced available N (AN), available P (AP) and total phosphorus (TP) in rhizosphere soil. Our results suggest that N addition alters the biomass, NSC, N concentrations, C:N and N:P ratios of all plant organs, but roots responded more strongly than stems or leaves to N addition, potentially allowing the plants to absorb more water from the arid soil in this region ensuring the survival of R. soongorica seedlings. Rhizosphere soil AP, AN and TP concentrations were important factors affecting the NSC concentrations and stoichiometric characteristics of R. soongorica.

Reaumuria soongorica is an important biological barrier for ecological protection in Gobi desert of the Northwest, China, where soil nitrogen availability is low. N deposition increasing significantly in Gobi desert, so that the response of R. soongorica to N enrichment may become a problem. However, little is known the effects of N addition on biomass, non-structural carbohydrates (NSC), and carbon:nitrogen:phosphorus (C:N:P) stoichiometry of R. soongorica in this region. Here, we examined changes in biomass, NSC and C:N:P ratios of different organs for one year growth of R. soongorica at four N treatments which is 0 (N0), 4.6 (N1), 9.2(N2), and 13.8 (N3) g m−2 year−1. The N addition ( reach to 9.2 g m−2 year−1) significantly enhanced the biomass of different organs, meanwhile the belowground:aboveground ratio was also significantly increased. The NSC concentration of root significantly enhanced under N addition treatments, but the stem and leaf NSC concentration was only increased significantly at N1 and N2 addition. N addition only enhanced the soluble sugar concentration of leaf and root, and reduced starch concentration of different organs. The N concentration of stem and root were significantly enhanced at N2 and N3 addition and the leaf N concentration was only increased in N3 addition, but N addition had no significant effect on C and P concentrations. The stem and leaf C:N ratio were reduced significantly in N2 and N3 treatments, but the root C:N ratio was decreased significantly in N addition. The N3 addition significantly increased N:P ratio of different organs. Our results suggested N addition changed the biomass, NSC, N concentration, C:N and N:P ratio of different organs, meanwhile the root responded more strongly than stem or leaf, this is beneficial for absorbing more water in arid soil in this region, then to ensure the survival of R. soongorica seedlings.