氧化亚氮(N2O)是一种主要的温室气体。为探究旱作紫花苜蓿(Medicago sativa)生长年限对草地N2O释放通量的影响,采用静态箱—气相色谱法,分别观测了黄土高原休闲地和3、4、10龄紫花苜蓿草地N2O释放通量。与实测值相比较,DNDC(脱氮—分解)模型对苜蓿草地N2O释放的模拟具有较高的可靠性。另外,利用DNDC模型对苜蓿地N2O释放量进行估算。结果表明:与休闲地比较,高龄苜蓿草地N2O释放通量高于低龄苜蓿草地;N2O负通量观测值与模型模拟值差异较大;DNDC模型对不同龄苜蓿草地的模拟中发现,N2O释放主要集中在170~240 d,且波动较大,释放峰值出现在第210 d。DNDC 模型能够较好地模拟黄土高原苜蓿草地N2O释放通量,但其对苜蓿草地N2O负通量的模拟还需进一步改进。
Nitrous oxide (NO2) is a major atmospheric greenhouse gas. The soil physical properties and fertility will directly affect the production and release of NO2. Alfalfa has the advantages to improve soil physical properties and fertility,and the soil physical and chemical properties variation degree is associated with fixed the number of alfalfa planting years. A static chamber-HPLC method was used to detect NO2 emission fluxes in the fallow field,3,4,and 10 years-aged lucerne (Medicago sativa) field at the Loess Plateau. In addition,the DeNitrification-DeCoposition (DNDC) model was also applied to estimate the NO2 emission variations in our study,which fit pretty well with the measured NO2 emission fluxes. Compared to the fallow field,observed values of the N2O emission increased with the ages of lucerne field. Interestingly,the detected negative NO2 emission values in our analysis were disparate with the model calculations. The time of released NO2 from differently aged lucerne field fluctuated and accumulated highly between 170-240 days during the growing season,the most release was estimated at 210 day in the DNDC model. Although the DNDC model could estimate the NO2 emission fluxes in lucerne field at the Loess Plateau,further parameter modifications are required to include the negative flux emissions in the analysis.
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