Abstract: To investigate the effects of elevated CO₂ concentration \[CO₂\] and nitrogen fertilization on the content and accumulation of non-structural carbohydrate (NSC) in stem sheath of rice, a Japonica rice (Oryza sativa L.) ‘Nanjing 9108’ was grown in a OTC pot experiment with three CO₂ concentrations: ambient (T0), ambient+120 μmol·mol^-1 (T1), and amibent+200 μmol·mol^-1 (T2) in opentop chambers (OTC), and three nitrogen (N) fertilization levels: 10 g N·m^-2 (N1), 20 g N·m^-2 (N2), and 30 g N·m^-2 (N3). We measured aboveground biomass, NSC content in stem sheath and nitrogen content in the top four leaves at heading, filling (20 d after heading), and mature stage. Results showed that there was no significant effect of elevated \[CO₂\] on N content in leaves at the heading stage, while it significantly reduced the N content in leaves at N2 and N3 levels during the filling stage. Elevated \[CO₂\] did not affect the content and accumulation of NSC in stem sheath at the heading stage. The accumulation of NSC in stem sheath significantly increased when the pots were transferred to higher \[CO₂\] at the heading stage, but significantly decreased when the pots were transferred to lower \[CO₂\] at the heading stage. Under the same \[CO₂\], both the content and accumulation of NSC were N1>N2>N3, being significantly higher under N1 than under N3. There was no significant difference in rice yield at different \[CO₂\], but the yield increased with the increasing N fertilization levels. Elevated \[CO₂\] and N fertilization levels significantly interacted to affect the content of NSC in stem sheath during the filling period. The content and accumulation of NSC in stem sheath at the heading and filling stages were positively correlated with dry weight of stem sheath and negatively correlated with N content in leaves. The slower N attenuation in leaves, the lower NSC residual ratio (R_NSC) was. There was a significant negative correlation between seed setting rate, yield and R_NSC at the filling stage, suggesting that there would be less NSC transferred out from stem sheath, lower seed setting rate and lower yield with higher R_NSC.

Key words: ecological source, ecological security pattern, geological disaster sensitivity, ecological importance, ecological corridor.