硝化作用对盐碱湿地N_2O排放的影响及其环境因子分析

Effect of Nitrification on N_2O Emissions and Their Environmental Factors in Saline-alkali Wetlands

湿地是温室气体氧化亚氮(N_2O)重要的源或汇,盐碱湿地作为湿地的重要组成部分,研究其N_2O排放对于探究盐碱湿地N_2O产生的硝化作用机制及评估其在温室效应中的作用具有重要意义.本文对代表性盐碱湿地——扎龙芦苇沼泽湿地生长季的N_2O释放量及相关环境因子进行了研究.结果表明,生长季N_2O通量呈波动性下降趋势,最大值出现在7月中旬,平均排放通量为(37. 49±15. 75)μg·(m2·h)-1,表现为N_2O的释放"源". N_2O通量与不同深度土层温度存在显著正相关关系(P <0. 05),且上层土温对N_2O排放的影响程度高于深层土;淹水期间N_2O通量与积水深度呈显著负相关关系(P <0. 05);且土壤TOC和TN含量较低,N_2O通量与0～40 cm土层NH+4-N含量呈显著正相关关系(P <0. 05),而与NO-3-N含量没有关系,硝化作用程度要比反硝化强;此外,土壤氨氧化菌活性与0～20 cm土层温度存在极显著正相关关系(P <0. 01),且N_2O通量与氨氧化菌活性也呈极显著的线性正相关关系(P <0. 001),表明盐碱湿地的N_2O释放受硝化作用影响巨大.

Wetlands are important sources and sinks for N2O. Exploring the role of N2O emissions in saline-alkali wetlands has great significance in understanding the nitrification mechanism of N2O production and assessing the role of saline-alkali wetlands in the greenhouse effect. The present study examined the N2O fluxes and environmental factors of a typical Zhalong reed wetland during the growing season. The results suggested that the N2O fluxes tended to decrease in volatility,with the highest value in mid-July. The mean flux of N2O was( 37. 49 ± 15. 75) μg·( m2·h)-1,indicating that the typical Zhalong reed wetland was a source of N2O. The N2O fluxes exhibited a significantly positive correlation with soil temperature at different depths( P < 0. 05),and the impact of the upper soil temperature on N2O flux was higher than that of deep soil. In the flooding period,the relationship between N2O fluxes and water table depth was negatively correlated( P < 0. 05). Meanwhile,the TOC and TN contents were lower,and the N2O flux was significantly positively correlated with the NH+4-N content in the 0-40 cm soil layer( P < 0. 05),but it was not related to NO-3-N content. Nitrification was stronger than denitrification. There was a significant positive correlation between ammonia-oxidizing bacterial activity and soil temperature in 0-20 cm layer( P < 0. 01). Additionally,the activity of ammonia-oxidizing bacteria also presented significantly positive linear correlation with the N2O fluxes( P < 0. 001),which indicated that the release of N2O in saline-alkali wetlands was greatly affected by nitrification.