白洋淀湿地芦苇型水陆交错带土壤氮素形态变化和N_2O排放特征及氮储量研究

为探究以芦苇群落占主导的湖泊生态系统的水陆交错带湿地固氮功能及氮循环的变化特征,以白洋淀湿地为研究对象,于2015年3—11月通过野外定点调查监测方法研究了芦苇型水陆交错带土壤氮素形态的季节动态变化和N_2O排放特征及其氮储量。结果表明:白洋淀芦苇型水陆交错带土壤N_2O排放通量具有明显的季节变化特征,主要表现为先小幅上升(3—4月)后降低(5月),随后急剧上升到峰值(8月份),之后又急剧下降(9—11月)的变化趋势。3月和11月土壤N_2O排放通量低于15μg/(m~2·h),8月份达到峰值141.01μg/(m~2·h)(S1)和208.41μg/(m~2·h)(S2)。白洋淀芦苇型水陆交错带土壤中氮素主要以有机氮形式存在,各土层有机氮含量占全氮含量的97%以上,且主要集中在土壤表层,随土层深度的增加而降低。各层土壤全氮含量在6、8月份时相对较高,且主要集中在40cm以上土层。另外,1m土体内,全氮含量也表现为随土层深度的增加而降低。白洋淀芦苇型水陆交错带各土层NH_4~+-N和NO_3~--N含量在10月份较其它月份高。在1m土壤剖面中,NH4+-N含量的变化差异较小,NO_3~--N含量呈现随土层深度增加先降低后又上升趋势。水陆交错带土壤氮密度均由表层向下逐渐下降,受生活污染较严重的S_1和受渔业生产污染相对较重的S_2的1m深土壤氮密度分别为1386.079g/m~2和1434.91g/m~2,其中60cm以上土层的贡献率均达到了70%以上。

Studies on variation characteristics of soil nitrogen forms,nitrous oxide emission and nitrogen storage of the Phragmites australis-dominated land/inland water ecotones in Baiyangdian wetland

In order to explore the characteristics of nitrogen fixation and nitrogen cycling in the ecotones of the lake ecosystem dominated by Phragmites communis community.The Baiyangdian wetland was chosen as the typical site to study the seasonal variation characteristics of soil nitrogen forms,N2O emission and nitrogen storage of the Phragmites australis-dominated land/inland water ecotones using field investigation method during the period of March to November 2015.The results showed that the N2O emission showed a seasonal dynamic.Generally speaking,the N2O emission showed a slight increase at first(in March and April)and then decrease(in May),followed by a sharp rise to a peak value(in August),and later a sharp decline (September to November).The emission flux of N2O were relatively low in March and November,which were less than 15 μg/(m2 · h),peak values were 141.01 μg/(m2 · h)(S1)and 208.41 μg/(m2 · h)(S2)in August,respectively.Organic nitrogen was the main existing form of soil nitrogen in the Phragmites australis-dominated land/inland water ecotones in Baiyangdian Lake,which accounts for over 97％ of the total nitrogen and mainly concentrated in the surface soil,and its content decreased with the increase of soil depth.The total nitrogen content in every soil layer was relatively high in June and August,which mainly concentrated in the soil layer of 0-40 cm and also decreased with the increase of soil depth within 1 m soil profile.The soil NH4+/-N and NO3--N in every soil layer were relatively high in October.Within 1 m soil profile,the change of NH4+/-N content was small while the soil NO3--N content was decreased at first and then increased with the increase of soil depth.The soil nitrogen densities in the 1 m depth of the land/inland water ecotones were gradually decreased from the surface layer.The nitrogen densities of S1 with serious rural domestic pollution and S2 with serious production pollution were 1386.07 g/ m2 and 1434.91 g/m2,respectively.The contributing rates of soil layers above 60 cm accounted for more than 70％.