四川桤柏混交林土壤N2O排放的实测与模拟

采用静态箱-气相色谱法对川中丘陵区桤柏混交林土壤N2O排放进行了连续两年的测定.通过与Forest-DNDC模型模拟进行对比分析,结果表明,模型能够较好地模拟林地土壤N2O排放.2005和2006年模型模拟的土壤N2O年平均排放速率为15.02,14.03mg/(m2×h),分别为实际观测值的85.7%和87.5%.2005和2006年的实际观测值与模型模拟值之间差异均不显著(P>0.05),模拟有效系数分别为0.56和0.51.以2005年降雨量和气温为基准利用模型进行情景分析,结果表明,本地区降雨量在±30%范围内变化时,林地土壤N2O排放量的变化幅度不超过25%;气温在±3℃范围内变化时,林地土壤N2O排放量的变化幅度不超过10%.

Measurement and simulation of N2O emissions from a alder and cypress mixed plantation in hilly areas of the central Sichuan Basin

Soil N2O efflux in a mixed forest plantation of Alnus cremastogyne and Cupressus funebris was measured by closed chamber chromatographic technique from 2005 to 2006 in the central Sichuan Basin. Simulations of N2O emissions revealed that field observations and model predictions fitted well for seasonal patterns of both years. The simulation of mean soil N2O emission rate were 15.02mg/(m2×h) and 14.03mg/(m2×h), which accounted for 85.7% and 87.5% of field measurements in 2005 and 2006, respectively. There were no significant differences between predicted and measured N2O fluxes both in 2005 and 2006. The modeling efficiency was 0.56 and 0.51 in 2005 and 2006, respectively. The results obtained from both sensitivity analysis and validations with field data sets indicated that Forest-DNDC could be successfully used to predict N2O emissions in this forest sites. In comparison with the precipitation and air temperature in 2005, changes in precipitation by ±30% could only change the N2O fluxes by less than 25%, and changes in air temperature by ±3℃ could only change the N2O fluxes by less than 10%.