DNDC模型对北京旱地农田N_2O排放的模拟对比分析

Comparative Analysis on Measured and DNDC(DeNitrification-DeComposition) Modeled N_2O

通过DNDC(Version77)模型和田间原位观测,对北京地区大豆农田的N2O排放特征进行了模拟与对比分析。结果表明,DNDC模型能较好地模拟田间实测到的大豆生长期内N2O排放通量、气温和土壤地表温度的变化和N2O排放对每日降水的响应。但模型还存在一些问题:对于干旱期和非农业活动期农田的N2O排放反应灵敏度不够,模型低估了干旱期和非农业活动期农田的N2O排放通量。总的来说,在以生长期为时间尺度的计算上,模拟和实测值总量相差不大,在将来北京地区旱地农田N2O排放量估算上有很强的应用价值。为了进一步确定影响大豆生长期内N2O排放的主要因子,本文还进行了敏感性实验分析。结果表明,在一定范围内,在其他条件不变的情况下,N2O-N排放模拟值对土壤初始表面有机碳含量的变化较为敏感,随着土壤初始表面有机碳含量的增加,N2O-N排放模拟值也随着线性增加;另外,N2O-N排放模拟值对降雨中N素的含量变化也较为敏感,随着降雨中N素的含量的升高,N2O-N排放模拟值也随着非线性增加。

The present paper deals with simulation and contrastive analysis o n N2O emission characters from soybeans farm in Beijing through DNDC (version 77) model and a farm automatic sampling system. The results showed that DNDC model w as well applied to simulate the N2O emission flux, air temperature and soil surf ace temperature changes from soybean growth period from the farm. The response o f N2O emission flux to daily precipitation; but there were some problems that th e response sensitivity was not enough about N2O emission simulation value to dry land period and non-agriculture activities. N2O emission flux during drought a nd non-agriculture activities periods was lower than estimated by the DNDC. How ever, during the time scaling for growth, there was small gap between the simula ted N2O emission fluxes and measured ones. This meant that the model can be well applied to estimate upland farm N2O emission fluxes in the future . In order to confirm primary factors affecting N2O emission during soybeans growth term, the analysis for sensitivity experiment were made under some ranges when which othe rs conditions were kept invariability. The results showed that N2O-N emission s imulation value was more sensitivity than change of soil surface organic C conte nt, with increasing of soil surface organic C content,N2O-N emission simulatio n value increase with linearity. In addition,N2O-N emission simulation value a lso was more sensitivity to change of N content in rainfall,while with increasi ng of N content in rainfall period,N2O-N emission simulation value increased w ith non-linearity .