Abstract: Taking the China rice/wheat FACE (Free-Air Carbon Dioxide Enrichment) as a platform, this paper studied the effects of elevated CO₂ on the NH₄⁺-N and NO₃^--N contents at different depths of paddy soil in rice season. Under elevated CO₂, the NH₄⁺-N content in plough layer increased at early growth stage but decreased at late growth stage, and the soil NO₃^--N content at the depths 5, 15, 30, 60, and 90 cm increased by 46.5%, 36.8%, 23.3%, 103.7%, and 42.7%, respectively, with a significant increase occurred at the depths 60 cm (P<0.01) and 90 cm (P<0.05), compared with the control.

Key words: elevated atmospheric CO₂, rice season, paddy soilpaddy soil, NH₄⁺-N, NO₃^--N, Gleditsia microphylla, NaCl stress, salt injured index, salt tolerance ability.