黄河口典型湿地土壤氮素的季节动态及转化过程研究

Study on Seasonal Variation Characteristics and Transformation Process of Soil Nitrogen in Yellow River Estuary Wetland

于2008年10月、2009年5月和8月对黄河口湿地进行了3次野外调查和室内及野外模拟实验,研究了湿地土壤中各形态氮素的季节变化及转化过程,结果表明:农业种植区表层土壤氮素含量明显高于自然湿地,自然湿地全氮的含量低于1 000 mg/kg,铵态氮含量小于10 mg/kg,硝态氮含量小于3 mg/kg,研究区土壤氮素含量处于低营养水平。土壤中氮素的含量8月份最低,其中无机氮的季节变化较有机氮明显;0-10 cm表层土壤氮素含量明显高于下层土壤,10 cm以下氮含量无显著垂直变化。在氮素的转化过程中,氮的反硝化能力最强,硝态氮的最大损失量达到23.44 g/(m3.d),这与研究区域土壤中硝态氮含量较低相吻合;矿化能力较弱,有机氮的最大转化量仅为0.91 g/(m3.d);氮的硝化过程中铵态氮的最大转化量为12.77 g/(m3.d)。芦苇枯落物在分解过程中发生了氮素的净释放,夏季淹水环境芦苇枯落物氮素的日均归还量最高,达到0.039 g/(m2.d),冬季最低,芦苇枯落物分解对土壤氮库的储量有一定影响。

Three field investigations and simulation experiments indoor and outdoor were made separately in October 2008,May and August 2009 in the Yellow River estuary wetland,and the results showed that： Nitrogen contents in agriculture area soil were higher than those in natural wetlands;Total nitrogen content was less than 1 000 mg/kg,ammonium nitrogen content less than 10 mg/kg,and nitrate content less than 3 mg/kg in the natural wetlands.The nitrogen content in the surface soil lied in a low nutrition level.Nitrate content was the lowest in August,and seasonal variation of inorganic nitrogen was much more obvious than organic nitrogen.In the vertical direction,the nitrogen content of 0-10 cm layer was significantly higher than that below 10 cm,while the soil nitrogen content below 10 cm had little change.In the transformation process,denitrification capacities were the strongest,and the maximum loss amount of nitrate nitrogen was 23.44 g/（m3·d）,which was consistent with low content of soil in the study area;Mineralization capacities was weaker,the transformation amount of organic nitrogen was only 0.91 g/（m3·d）;The amount of ammonia nitrogen transformation was 12.77 g/（m3·d）.Nitrogen was net released during the decomposition of reed.The amount of returned N of reed was highest in summer,lowest in winter,and the returned amount of nitrogen of reed was up to 0.039 g/（m2·d） during decomposition process,which affected the nitrogen reserves in soils.