无机氮添加对湿地土壤CO2和N2O排放影响

Effects of inorganic nitrogen addition on CO2 and N2O emissions from wetland soil

碳氮是陆地生态系统最为重要的两大元素,具有高度耦合性,通过生物地球化学过程影响全球环境。湿地是重要的陆地碳汇,特殊环境特点导致土壤有机碳大量积累,大气氮沉降和人类活动引起的土壤氮可利用性增加将严重影响湿地碳氮循环过程。然而,不同形态比例的无机氮添加对湿地土壤CO 2和N 2 O排放变化影响还不清楚。本研究以三江平原小叶章季节性积水沼泽湿地和水稻田0~10 cm、10~20 cm土层土壤为研究对象,开展不同比例NH+4-N/NO-3-N添加(1∶0、3∶1、1∶1、1∶3和0∶1,即T1、T2、T3、T4和T5)对CO 2和N 2 O排放影响研究。结果表明,与对照不添加氮相比,不同比例NH+4-N/NO-3-N添加后CO 2排放明显降低,其中小叶章湿地和水稻田0~10 cm土层CO 2排放分别降低了25.6%(T1)~51.0%(T5)、21.2%(T3)~42.6%(T4),10~20 cm土层则降低了4.39%(T3)~34.5%(T5)、20.4%(T1)~33.2%(T4),CO 2排放随NO-3-N的增加而减少;NH+4-N/NO-3-N添加后小叶章湿地不同土层N 2 O排放变化没有明显规律,但水稻土N 2 O排放显著增加(T5处理除外)。培养结束后,小叶章湿地和水稻土壤微生物量碳在不同无机氮添加处理、不同土层间表现出不同的变化特点。通过合理管理农业生产活动中无机氮肥种类搭配的使用可以促进湿地土壤碳固定,减缓N 2 O排放,进而减缓全球变暖进程。

Carbon(C)and nitrogen(N)are the two most important elements in the terrestrial ecosystems,and they are highly coupled and affect the global environment through biogeochemical processes.Wetland ecosystem is an important terrestrial C sink,and accumulates a large amount of soil organic C.The increase of soil N availability caused by atmospheric N deposition and human activities may seriously affect the C and N cycling processes in wetland ecosystems.However,the effects of different inorganic N forms on wetland soil CO 2 and N 2 O emissions are still not clear.In this study,we selected the seasonal flooded wetland with Deyeuxia angustifolia and paddy soils at 0-10 cm and 10-20 cm depths to examine the effects of different ratios of NH+4-N/NO-3-N addition(1∶0,3∶1,1∶1,1∶3 and 0∶1,i.e.T1,T2,T3,T4 and T5)on CO 2 and N 2 O emissions in the Sanjiang Plain.The results showed that CO 2 emissions significantly decreased after different ratios of NH+4-N/NO-3-N additions.Compared with the control,the CO 2 emissions decreased by 25.6%(T1)~51.0%(T5)and 21.2%(T3)~42.6%(T4)in the 0-10 cm depth soils,and 4.39%(T3)~34.5%(T5)and 20.4%(T1)~33.2%(T4)in the 10-20 cm depth soils,respectively.The CO 2 emission decreased with the increment of NO-3-N addition.N 2 O emissions in different depths of wetland soil had no obvious change after varied NH+4-N/NO-3-N addition,while significantly increased in the paddy soil(except T5 treatment).The microbial biomass C of wetland and paddy soil showed different characteristics with different inorganic N addition treatments and soil layers at the end of the incubation experiment.Our results indicated that managing inorganic N fertilizers would increase the soil C sequestration and decrease the emissions of N 2 O in wetlands,which will help to slow down the global warming process.