关键词: 土壤氮有效性, 氮矿化, 降水变化, 土壤深度, 控制实验, 塞罕坝地区

Abstract: The contents of inorganic Nitrogen (N) and rates of soil N mineralization at soil depths of 0?5, 5?10,10?20 and 20?30 cm were measured by a field manipulative experiment of ±30% throughfall and closed-top tube incubation method in a Pinus sylvetris var. mongolica plantation at PKU-SOGES, China. The results show that the contents of inorganic N, NH₄⁺-N, and NO₃^--N at the soil depths of 0?30 cm are 6.70±2.31, 5.59±1.78, 1.11±0.77 mg/kg, respectively. There is no significant difference among inorganic N contents of different soil depths and throughfall treatments but the NO₃^--N of +30% is lower than that of control. Net N mineralization rates of 0?30 cm was ?0.24 (?6.65 to 10.24) mg/(kg?30d). Throughfall treatments and soil depths have no significant effects on net ammonification rates. According to the net nitrification rates and net N mineralization rates, both of them at 0?5 cm are significantly higher than those at other soil depths, and treatments of ±30% throughfall are higher than the control. In a word, both the ±30% throughfall treatments decrease inorganic N, and increase net N mineralization rates. The results also indicate that impacts of precipitation change on soil NH₄⁺-N and ammonification are weaker than those on NO₃^--N and nitrification. This study will contribute to assessment of precipitation changes on plantation ecosystem service and N biogeochemical cycle.

Key words: soil nitrogen availability, nitrogen mineralization, precipitation change, soil depth, manipulative experiment, Saihanba