| Food security is an important guarantee for world peace and development.It is an important foundation for building a community of shared future for mankind.China has made great efforts in food supply security.Agriculture is an important source of reactive nitrogen emissions,which have significant impacts on the environment and human health.The influence of food supply security on gaseous reactive nitrogen（GNr）emissions in agricultural systems involves many complex processes and uncertain factors.These processes and factors would change the characteristics of GNr emissions in supply chain of the agricultural systems.Considering the dynamic reactive nitrogen losses of regional agricultural systems,this paper explored the relationship between crop planting structures and degree of food self-sufficiency,and predicted the distribution characteristics of GNr emissions in agricultural systems under the background of regional food supply security in the future.Specifically,a hybrid approach,which incorporated life cycle analysis,Copula–Markov chain Monte Carlo（MCMC）simulation,and experimental design,was proposed.The method was used to identify the emission characteristics of reactive nitrogen in agricultural systems,the correlation between crop planting structures and degree of food self-sufficiency,and the uncertain emission characteristics of GNr in agricultural systems under the background of food supply security.The approach was proven to be of benefit in（a）evaluating GNr emissions in crop planting and livestock breeding process based on a life cycle analysis framework,（b）identifying dependencies and co-movements of the correlated variables in planting structures and food self-sufficiency rate using Copula–MCMC simulations,and（c）recognizing fluctuations in GNr emissions of crop planting and livestock breeding process in the future using experimental design method,which was based on sampling.To verify the applicability of the method,the major planting areas of wheat,soybean,corn and rice in China（mainly covering 24 provinces）were selected during the crop planting process.The research areas of livestock and poultry breeding process were included most of the provinces in China except the Hong Kong,Macao and Taiwan to explore the distribution characteristics of GNr emissions in agricultural systems under the background of food supply security in this study.The following results were obtained:（1）The results of life cycle analysis of GNr emissions in agricultural systems showed that fertilized soil caused more than 90%of GNr emissions during the crop planting process.The GNr emissions during the livestock and poultry breeding process mainly occurred in the stages of manure management and feed crop production.In the manure management stage,the quantity of NH3-NOx accounted for more than 90%of the total GNr emissions.（2）The correlation analysis results based on Copula-MCMC simulation indicated the obvious correlation between crop planting structures and food self-sufficiency rate.Compare with the planting structures in 2020,the planting structures of corn and soybean in Shanxi and Heilongjiang would increase the most in 2025 and 2030,respectively.On the contrary,the planting structures of wheat and rice in Xinjiang and Fujian would decrease the most in2025 and 2030,respectively.In term of production of livestock and poultry products,the pork and lamb production would be the largest and the smallest in 2025 and 2030,respectively.（3）The prediction results of GNr emissions showed that with the influence of crop planting structures and sowing areas,the GNr emissions in Heilongjiang Province would be the largest,while the GNr emissions in Fujian Province would be the smallest.With the promotion of food security policies,GNr emissions from the crop production of China in2025 and 2030 would increase by 12.12%and 24.63%,compared with those in 2020（i.e.,1893.04 kt N）.In the process of livestock breeding,the GNr emissions from mutton production would vary more obviously than those from other livestock and poultry productions in 2025 and 2030.Compared with the mean of GNr emissions in livestock and poultry production in 2020（i.e.,13969.49 kt N）,the total GNr emissions would decrease by0.46%and increase by 9.00%in 2025 and 2030,respectively.With the increase of meat consumption in people’s diet,the proportion of feed grain consumption in China’s grain consumption is increasing gradually.In order to reduce the emissions of GNr in agricultural systems,policymakers should pay close attention to the feed grain problem as well as the ration problem. |
