向海沼泽湿地芦苇中氮含量动态变化和循环特征

Dynamic Changes of Nitrogen Contents and Nitrogen Cycling in Phragmites australis of Xianghai Marsh Wetland

以向海湿地自然保护区二百方子湿地和付老文泡湿地的芦苇(Phragmites australis)为研究对象,探讨了开放型和封闭型湿地芦苇不同器官中氮含量动态变化特征。研究结果表明,二百方子湿地和付老文泡湿地芦苇不同器官全氮含量变化趋势一致,叶和茎的含氮量随季节变化均呈指数下降的变化趋势;穗氮含量呈线性下降变化趋势;而根和根状茎氮含量则呈先急剧增加后急剧减少再缓慢增长的非线性变化趋势。两种类型湿地芦苇的地上器官平均氮含量高于地下器官;各月芦苇叶氮含量高于茎杆氮含量,而根的氮含量则高于根状茎。除茎和穗外,付老文泡湿地芦苇叶、根和根状茎的平均氮含量均低于二百方子湿地芦苇。二百方子湿地芦苇对氮的吸收系数和利用系数均高于付老文泡湿地芦苇,但循环系数较低。

Little information is available on dynamic changes in nitrogen contents in wetland plants of inland alkaline wetlands.Nitrogen contents in different organs and litters of Phragmites australis in plant growth season were measured in order to study their dynamic changes in inland alkaline wetlands,i.e.Erbaifangzi and Fulaowenpao wetlands.Soil nitrogen contents and soil bulk density was also determined in order to reveal nitrogen cycle characteristics in soil and plant system.Results showed that similar changing trends in nitrogen contents in different organs of Phragmites australis with increasing months were observed in both wetlands.Nitrogen contents in the leaves and stems showed an exponential decrease with increasing months,while a linear decrease for spikes,with the goodness of fit of more than 0.85.However,the nonlinear changing tendency（i.e.,simple cubic equation） of ＂steep increasing-steep decreasing-slow increasing＂ was obvious for the roots and rhizomes,with the goodness of fit of more than 0.70.Generally,the mean nitrogen contents in above-ground organs were higher than those in below-ground organs in both wetlands.Nitrogen contents were higher in the leaves and spikes than those in the stems.Compared to rhizomes,nitrogen contents were higher in the roots.Except for stems and spikes,the mean nitrogen contents in the leaves,roots and rhizomes of Phragmites australis in Fulaowenpao wetland were lower than those in Erbaifangzi wetland.This implied that the leaves,roots and rhizomes of Phragmites australis in closed wetlands had higher use efficiencies compared to open wetlands.The uptake coefficient was lower in Xianghai wetland compared to other wetland,suggesting less nitrogen was transferred from soil to plants.The annual uptake nitrogen and annual retained nitrogen were slightly higher in Erbaifangzi wetland than Fulaowenpao wetland,while obviously higher annual returned nitrogen was observed in Fulaowenpao wetland compared to Erbaifangzi wetland.Similarly,the uptake coefficient of nitrogen was slightly higher for Phragmites australis in Erbaifangzi wetland,and there was obviously higher utilization coefficient.Moreover,in respective to Phragmites australis in Erbaifangzi wetland,the cycling coefficient of nitrogen was higher for Phragmites australis in Fulaowenpao wetland.