Abstract: An indoor experiment was conducted to study the effects of simulated nitrogen deposition on the soil available N in typical temperate forest stands. During the  experiment period, nitrogen deposition increased the soil NH₄⁺-N, NO₃^--N, and available N contents, as compared with the control, but the increments differed with stand types, soil layers, nitrogen treatment types, and treatment duration. Mixed forest soil had weaker responses in its available N contents to the nitrogen deposition than broad-leaved forest soil but stronger responses than artificially pure coniferous forest soil, and soil A horizon was more sensitive to nitrogen deposition than soil B horizon. Ammonium nitrogen deposition had larger effects on soil NH₄⁺-N content, nitrate nitrogen deposition had larger effects on soil NO₃^--N content, while mixed ammonium and nitrate nitrogen deposition increased the contents of both soil NH₄⁺-N and soil NO₃^--N, and the increments were higher than those of ammonium nitrogen deposition and nitrate nitrogen deposition, suggesting the additive effects of the mixed ammonium and nitrate nitrogen deposition on the forest soil available N.

Key words: nitrogen deposition, forest soil, available N, NH₄⁺-N, NO₃^--N