Simulation And Prediction Of Carbon Sequestration In Semi-arid Maize Farmland Ecosystems

With the development of human society,many environmental problems need to be solved urgently.Excessive consumption of fossil energy,destruction of ecological balance and other behaviors,result in the continuous rise of carbon dioxide concentration,causing serious greenhouse effect.In the process of global carbon cycle,farmland ecosystem can be carbon source or carbon sink.Therefore,it is of great significance to explore the carbon sequestration capacity of farmland ecosystem in crop growing season.The response of farmland ecosystems to climate change can mitigate greenhouse effect and maintain the carbon balance of ecological environment.In this paper,given the photosynthetic capacity of maize at different stages,carbon flux of agricultural ecosystem,and meteorological data,many factors affecting the carbon sequestration capacity of maize farmland ecosystem were analyzed,and we select the optimal model of maize photosynthesis responding to photosynthetic effective radiation under standard conditions.According to the relationship between top leaf photosynthesis and canopy photosynthesis of maize,there is a conversion coefficient.The Crop-C model was partially revised using the top leaf light response model and conversion coefficient,and the simulation effect of the revised model was tested.At the same time,the revised Crop-C model was used to simulate and predict the carbon sequestration capacity and efficiency of maize farmland ecosystem under different scenarios at the end of the 21 st century.The main conclusions are as follows:(1)Among the environmental factors,photosynthetic active radiation,temperature and carbon dioxide concentration had significant effects on the net photosynthetic rate of maize leaves and canopy.Yezipiao model can better simulate the light response curve of maize leaves under standard conditions.(2)Lloyd & Taylor model can better simulate the relationship between ecosystem respiration and temperature;There was a conversion coefficient related to leaf area index(LAI)between top leaf photosynthetic rate and canopy photosynthetic rate of maize plants.(3)The light response curve of the top layer of maize leaves was used to calculate the photosynthetic capacity of maize canopy instead of calculating it by measuring canopy nitrogen content in the Crop-C model.And the conversion coefficient related to leaf area index was introduced to partially revise the Crop-C model.According to the actual measured values,it is found that there is a quadric function relationship between the leaf area index and the conversion coefficient.The revised Crop-C model shows good simulation effect in the model fitting period and the verification period.(4)Under the assumption that solar radiation remains unchanged and the influence of temperature on maize phenology is not considered,the revised Crop-C model is used to simulate and predict the carbon sequestration capacity and efficiency of maize farmland ecosystem at the end of the 21 st century.The results showed that with the increase of temperature,the carbon sequestration capacity of maize farmland ecosystem increased,but the carbon sequestration efficiency decreased.