氮素类型和剂量对寒温带针叶林土壤N2O排放的影响  

The effects of types and doses of nitrogen addition on soil N_2O flux in a coldtemperate coniferous forest,northern China

作　　者：耿静[1,2] 程淑兰[2] 方华军[1] 于贵瑞[1] 徐敏杰[2] 王磊[1] 李晓玉[1] 司高月 何舜[2] 

机构地区：[1]中国科学院地理科学与资源研究所,生态系统观测与模拟重点实验室,北京100101 [2]中国科学院大学资源与环境学院,北京100049

出　　处：《生态学报》2017年第2期395-404,共10页Acta Ecologica Sinica

基　　金：国家自然科学基金项目(41471212,31470558,31290221,31130009,31290222);国家重点基础研究发展计划项目(2012CB417103);中国科学院地理科学与资源研究所“秉维”优秀青年人才基金项目(2011RC202);中国科学院战略性先导科技专项(XDA05050600)

摘　　要：大气氮沉降输入会增加森林生态系统氮素有效性,进而改变土壤N_2O产生与排放,然而有关不同氮素离子(氧化态NO_3^--N与还原态NH_4^+-N)沉降对土壤N_2O排放的影响知之甚少。以大兴安岭寒温带针叶林为研究对象,构建了3种类型(NH_4Cl、KNO_3、NH_4NO_3)和4个施氮水平(0、10、20、40 kg N hm^(-2)a^(-1))的增氮控制试验,利用流动化学分析仪和静态箱-气相色谱法4次/月测定凋落物层和矿质层土壤无机氮含量、土壤-大气界面N_2O净交换通量以及相关环境因子,分析施氮类型和剂量对土壤氮素有效性、土壤N_2O通量的影响探讨氮素富集条件下土壤N_2O通量的环境驱动机制。结果表明:施氮类型和剂量均显著影响土壤无机氮含量,土壤NH_4^+-N的积累效应显著高于NO_3^--N。施氮一致增加寒温带针叶林土壤N_2O排放,NH_4NO_3促进效应最为明显,增幅为442%-677%,高于全球平均水平(134%)。土壤N_2O通量与土壤温度、凋落物层NH_4^+-N含量正相关,且随着施氮水平增加而增加。结果表明大气氮沉降短期内不会导致寒温带针叶林土壤NO_3^--N大量流失,但会显著促进土壤N_2O的排放。此外,外源性NH_4^+和NO_3^-输入对土壤N_2O排放的促进作用具有协同效应,在未来森林生态系统氮循环和氮平衡研究中应该区分对待。Increasing atmospheric nitrogen （N） deposition would production and emission from N-limiting forest soils. However, it is ion （i.e., oxidized NO3^--N and reduced NH4^＋-N） deposition on soil cold-temperate coniferous forest in the Great Khingan region was change soil N availability, and thereby changes N2O still unclear about the contrasting effects of different N N2O emission in boreal forests. In the present study, a selected for conducting the manipulative N addition experiment, including three forms of N fertilizers （NH4Cl, KNO3, and NH4NO3） and four rates of N addition （0, 10, 20, and 40 kg N hm^-2 a^-1 ）. Soil-atmospheric N2O exchanging fluxes were measured four times per month using static chambergas chromatography. Simultaneously, soil temperature, moisture, and inorganic N contents were measured to explore how the main factors affect soil N2O emission. The results showed that the types and doses of N addition significantly changed soil inorganic N contents, and the accumulation of soil NH4^＋-N was significantly higher than that of soil NO3^--N due to N addition. N addition increased N2O emission from the boreal forest soil, and the NH4NO3 addition treatments promoted high soil N2O fluxes, with an increase of 442% to 667%, which was higher than the global average （134%）. There were positive correlations between soil N2O fluxes and soil temperature, and between soil N2O fluxes and soil NH4^＋-N contents in the litter layer. Soil N2O fluxes were driven by soil temperature, followed by soil NH4^＋-N contents in the litter layer. These findings suggest that atmospheric N deposition cannot lead to a significant soil NO3^--N leaching and loss in boreal forests over the short term, but it can significantly promote soil N2O emission. Furthermore, exogenous NH4^＋ and NO3^- inputs into boreal forests have synergic effects on soil N2O emission, which should be distinguished in N cycle and balance in terrestrial ecosystems using ^15N tracer methods in the future.

关 键 词：大气氮沉降 土壤N2O通量 氮素有效性 主控因子 北方森林 

分 类 号：S714[农业科学—林学]