尕海湿地区沼泽草甸生长季土壤碳氮组分对增温施氮的响应

Response of Growing Season Soil Carbon and Nitrogen Components to Warming and Nitrogen Addition in Marshy Meadows of the Gahai Wetland Area

[目的]为探究高寒湿地土壤碳氮组分对气候变暖和氮沉降的响应特征。[方法]以尕海湿地沼泽草甸为研究对象,采用开顶箱增温(OTC)和外源氮素(NH_(4)NO_(3))添加模拟未来气候变暖及氮沉降试验,分别设置对照(CK)、增温(W)、施氮(N)和增温施氮(WN)4种处理。在试验进行1.5年后对土壤碳氮组分含量进行测定。[结果](1)开顶箱增温装置提高0-20 cm土层平均温度1.126℃,显著降低0-10 cm土层土壤含水量(SMC)、pH、全氮(TN)、微生物量氮(MBN)、铵态氮(NH_(4)^(+)-N)、有机碳(SOC)和可溶性有机碳(DOC)含量,提高硝态氮(NO_(3)^(-)-N)含量。(2)施氮显著降低NH_(4)^(+)-N、SOC和10-20 cm土层微生物生物量碳(MBC)及DOC含量,增加土壤TN、MBN和NO_(3)^(-)-N含量。(3)增温施氮显著增加土壤SMC、TN、NO_(3)^(-)-N和MBC含量,降低MBN、NH_(4)^(+)-N和DOC含量。(4)相关分析显示,土壤水分与各理化因子均存在正相关性,土壤碳氮组分间均呈正相关性。[结论]模拟增温施氮缓解尕海湿地植物生长的温度和氮的限制,促进TN的积累,对土壤微生物量碳氮影响较大,导致土壤微生物量碳氮及分布特征发生转换。

[Objective]To examine the response characteristics of soil carbon and nitrogen fractions in alpine wetland soil to climate warming and nitrogen deposition.[Methods]Using open-top box warming(OTC)and adding exogenous nitrogen(NH 4NO 3)to simulate future climate warming and nitrogen deposition tests,four treatments were established,namely control(CK),warming(W),nitrogen application(N),and warming nitrogen(WN).The soil carbon and nitrogen levels were quantified after 1.5 years.[Results](1)The utilization of the open top box warming device resulted in a notable elevation of the mean temperature at 0-20 cm soil layer by 1.126℃.Additionally,this intervention led to a significant decrease in the water content(SMC)and pH levels,as well as the concentrations of soil total nitrogen(TN),microbial nitrogen(MBN),ammonium nitrogen(NH_(4)^(+)-N),organic carbon(SOC),and dissolved organic carbon(DOC)at the 0-10 cm soil layer.Conversely,there was an observed increase in the concentration of nitrate nitrogen(NO_(3)^(-)-N).(2)Nitrogen application considerably lowered the contents of NH_(4)^(+)-N and SOC in all the soil layers,as well as those of the contents of microbial biomass carbon(MBC)and DOC in soil layers 10-20 cm deep,but increased the contents of TN,MBN,and NO_(3)^(-)-N.(3)The application of nitrogen through warming conditions resulted in a large rise in SMC,TN,NO_(3)^(-)-N,and MBC content.Conversely,it led to a significant reduction in MBN,NH_(4)^(+)-N,and DOC.(4)Correlation analysis showed that there was a positive correlation between soil moisture and all physicochemical factors,and soil carbon and nitrogen components were positively correlated.[Conclusion]The results indicated that the simulated warming application of nitrogen alleviated the temperature and nitrogen limitation of plant growth in the Gahai wetland,promoted the accumulation of TN,and had a greater impact on the soil microbiota biomass carbon and nitrogen,which led to the conversion of soil microbial biomass carbon and nitrogen activities and distribution characteristics.