N addition alters non-structural carbohydrates and C:N:P stoichiometry in different organs of Reaumuria soongorica seedlings in Gobi Desert of the Northwest, China

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 (N 0 ), 4.6 (N 1 ), 9.2(N 2 ), and 13.8 (N 3 ) 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 N 1 and N 2 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 N 2 and N 3 addition and the leaf N concentration was only increased in N 3 addition, but N addition had no significant effect on C and P concentrations. The stem and leaf C:N ratio were reduced significantly in N 2 and N 3 treatments, but the root C:N ratio was decreased significantly in N addition. The N 3 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.