模拟氮沉降和CO2浓度增加对三江平原小叶章群落土壤总有机碳和氮素含量的影响

利用开顶气室(Open-Top Chamber,OTC),设置当前大气CO2浓度(370μmol.mol-1)、中等CO2浓度(550μmol.mol-1)和高CO2浓度(700μmol.mol-1)3个CO2浓度水平和不施氮(N1,0g N.m-2.a-1)、常氮(N2,5g N.m-2.a-1)、高氮(N3,10g N.m-2.a-1)3个氮素水平。研究了不同N沉降水平下,大气CO2浓度升高对以三江平原小叶章群落土壤有机碳和氮素含量的影响。结果表明:CO2浓度升高结合氮沉降连续运行两个生长季后,湿地土壤总有机碳含量没有显著变化,说明较短时间内大气CO2浓度升高和氮沉降不会使三江平原土壤有机碳含量产生变化。氮沉降引起各个土层的土壤全氮、铵态氮和硝态氮的含量增加,施氮水平越高土壤氮增加越多,但是全氮增加量不明显,铵态氮随施氮量的增加呈现极显著差异水平(P<0.01)。0～10cm,10～20cm土层土壤全氮、铵态氮的含量随着CO2浓度升高呈现出先增大后减小的趋势。土壤硝态氮含量在10～20cm土层含量变化与土壤全氮、铵态氮的变化趋势相同。说明大气CO2浓度一定程度的增加可以增加土壤的氮素含量,但是过量的大气CO2浓度反而会使得土壤氮素含量减少。

Effects of Simulated Nitrogen Deposition and Elevated CO2 Concentration on Soil Organic Carbon and Nitrogen of Deyeuxia Angustifolia Community on the Sanjiang Plain

An experiment was carried out with treatments differing in atmospheric CO2 concentration level(370,550 and 700 μ7mol·mol-1) and nitrogen supply(0,5 and 10 g N·m-2·a-1) on the OTC(Open Top Chamber)equipment for studying the effect of nitrogen deposition and elevated atmospheric CO2 concentration on the contents of soil organic carbon and nitrogen element which were contained in the Deyeuxia angustifolia community on the Sanjiang plain. The result indicates that the elevated atmospheric CO2 concentration in combination with nitrogen deposition consecutively envolves two growing seasons.There is no noticeable change in the content of soil organic carbon in the wetland.These illustrate that the elevated atmospheric CO2 concentration in combination with nitrogen deposition does not make the soil organic carbon change in a relatively short period of time.Nitrogen deposition caused by the total nitrogen of soils in various layers,NO-3-N and NH+4-N contents increased,and more nitrogen fertilizing led to more nitrogen increase.The increase of total nitrogen is not obvious in this process. Along with the increase of nitrogen fertilizer,NH+4-N contains obviously different levels(P<0.01)(0~10 cm,10~20 cm layers).Along with the increase of the CO2 concentration,the content of soil total nitrogen in 0~10 cm and 10~20 cm layers and NH+4-N showed a similar tendency,i.e.,firstly increasing and then decreasing.In the 10~20 cm layer,the content of NO-3-N's showed the same tendency with respect to soil total nitrogen and NH+4-N.,indicating that the increase of the atmospheric CO2 concentration can enhance the content of soil nitrogen element,but the atmospheric CO2 concentration excess will reduce the content of soil nitrogen element.