【目的】探究喀斯特森林土壤氮矿化特征及供氮能力。【方法】以贵州喀斯特原生乔木林和次生林为研究对象,采用树脂芯法,原位连续培养测定土壤氮矿化/硝化动态特征。【结果】(1)喀斯特原生乔木林和次生林土壤无机氮含量随培养时间延长存在明显的变化,NH_4~+-N含量呈先增加后减少再增加趋势,NO-3-N含量表现为总体增加趋势。NH_4~+-N是土壤有效氮的主要存在形式,其含量占土壤无机氮的84.57%~94.31%。(2)两演替群落土壤氮矿化速率呈“V”形变化,范围分别为-0.43~0.97 mg/(kg·d)和-0.91~1.43 mg/(kg·d);硝化速率呈波动上升趋势,范围分别为0.21~0.49 mg/(kg·d)和0.03~0.31 mg/(kg·d)。(3)原生乔木林土壤无机氮含量、矿化速率、氨化速率和硝化速率均高于次生林。(4)原生乔木林土壤氮全年净矿化总量170.82 kg/(hm~2·a),是次生林的2.48倍,两种林分土壤净硝化氮分别占净矿化氮的95%和100%。【结论】喀斯特森林土壤供氮能力较强,但土壤氮矿化过程中氮硝化占主导,表明土壤中植物可利用的氮素易于淋溶或挥发损失。 【Objective】 The objective of this study was to investigate the characteristics of nitrogen mineralization and its nitrogen availability in Karst forest. 【Method】 The primary arbor and secondary forests in karst area of ​​Guizhou Province were selected as the research objects. The resin core method and in situ continuous culture were used to determine the dynamic characteristics of soil nitrogen mineralization / nitrification. 【Result】 (1) The content of inorganic nitrogen in karst primary tree and secondary forest changed obviously with the prolongation of culture time. The content of NH_4 ~ + -N increased at first, then decreased and then increased, and the content of NO-3-N increased trend. NH_4 ~ + -N is the main form of soil available nitrogen, accounting for 84.57% ~ 94.31% of the soil inorganic nitrogen. (2) The soil nitrogen mineralization rate of two successional communities varied from -0.43 to 0.97 mg / (kg · d) and from -0.91 to 1.43 mg / (kg · d), respectively. The rate of nitrification The fluctuation ranged from 0.21 to 0.49 mg / (kg · d) and from 0.03 to 0.31 mg / (kg · d), respectively. (3) The content of inorganic nitrogen, mineralization rate, ammonification rate and nitrification rate of native arbor forest were higher than that of secondary forest. (4) The annual total net nitrogen mineralization of native arbor forests was 170.82 kg / (hm ~ 2 · a), which was 2.48 times of that of the secondary forest. The net nitrogen nitrification in the two types of forests accounted for 95% 100%. 【Conclusion】 Karst forest soil has strong nitrogen supply capacity, but nitrogen nitrification is dominant in soil nitrogen mineralization process, indicating that plant available nitrogen in soil is easily leached or volatilized.