采用淹水厌氧密闭培养-乙炔抑制法测定了长白山4种森林土壤的反硝化势以及气态产物N2O、NO和N2的产生量.供试4种森林土壤均呈酸性,pH(H2O)4.5～5.3,有机碳含量24.6～83.0 g kg-1.结果表明,长白山4种典型森林土壤反硝化势及反硝化产物中氮氧化物的比例差异很大.土壤反硝化势强弱顺序依次为:阔叶红松＞白桦＞红松云杉冷杉＞兴安落叶松,与土壤有机碳和全氮含量呈显著的正相关关系(p＜0.01),与土壤pH的相关性不显著.比较加乙炔和不加乙炔处理发现,在培养过程中,N2O始终是反硝化的主要产物,占反硝化产物的比例变化于50%～85%之间,不随培养时间而发生显著的变化,与土壤pH呈弱负相关关系(p=0.22).反硝化产物中,NO仅占0.2%～2.4%,随培养时间也未发生有规律的变化,与土壤有机碳含量呈显著的对数负相关关系(p＜0.05).上述结果表明,长白山森林土壤反硝化过程并不能有效地将活性氮转化为惰性氮,反硝化作用的生态环境意义需要重新评估.%Denitrification and its products (N2, N20 and NO) in four forest soils collected from the Changbai Mountains were investigated with the acetylene inhibition method, which had soil samples in flasks flooded with water and incubated anaerobically with the headspace filled with N2. The four forest soils tested were all acid, with soil pH varying in the range from 4.5 to 5.3 and organic carbon in the range of 24.6 ～ 83.0 g kg-1. The results show that the soils differed greatly in denitrification potential, following a decreasing order of Pinus koraiensis ＞ Betula platyphylla Suk. ＞ Pinus koraiensis-Picea asperata ( Mast. )-Akjes fabri ( Mast. ) ＞ Larix gmelini ( Rupr. ) in denitrification potential, which was positively and significantly related to soil organic carbon and nitrogen content (p ＜ 0. 01 ), but insignificantly to soil pH. Comparison between the treatments with acetylene and the treatments without acetylene indicates that during the period of incubation, N20 was always the dominant product of denitrification, accounting for 50％ ～ 85 ％ of the total denitrification products, which did not vary much with the time of incubation and was weakly and negatively related to soil pH(p =0. 22). NO was a minor product of denitrification, accounting only for 0. 2％～2. 4％ , and in a significant negative logarithm relationship with soil organic carbon content (p ＜ 0. 05). These results imply that denitrification process would not effectively transform reactive nitrogen into inert nitrogen (N2) in the Changbai Mountain forest soils and the significance of the denitrification in removing reactive nitrogen should be re-assessed.
展开▼
