Study On Variation And Estimation Model Of Maize Carbon Flux Based On Eddy Covariance In South Of Anhui Province

In the context of global climate change,carbon flux cycle between atmospheric and terrestrial ecosystems has become a research focus in scientific community.Farmland ecosystems are the ecosystems most affected by human activities and have made outstanding contributions to the carbon cycle of entire terrestrial ecosystem.The carbon cycle has made a significant contribution.Therefore,researching the carbon flux of farmland ecosystems is of great significance for further understanding of the carbon cycle of terrestrial ecosystems.The eddy covariance technique was used to observe the carbon flux of maize farmland ecosystem in the hilly area of southern Anhui Province.And its variation and control mechanism of carbon flux were analyzed,and the time distribution characteristics of carbon source/sink properties were clarified.The change of carbon fixation efficiency of maize field was also explored.Finally,two main carbon flux models were validated and compared,and the applicability of the model to the simulated maize field carbon flux under different conditions was clarified.The main results are here:(1)Maize field is a carbon source at night,carbon sink during the day.Summer maize is a carbon source in the early and middle stages,and carbon sink in the later stage.Spring maize is carbon sink throughout the growth period.The intraday variation of maize carbon flux is characterized by a “U”-type single-peak curve that is stable at night,falling first and then rising during the daytime in cloudy and sunny day of early stage,or a “W”-type double-peak curve with a short-term rebound at noon in sunny day of later stage.In addition,maize field has strong carbon source properties under high temperature conditions.(2)The intraday variation of carbon fixation efficiency of maize field increased first and then remained stable and finally decreased.The carbon fixation efficiency of summer maize in the early and middle stages(jointing stage,heading stage)was lower than that of spring maize,and in the later stage(filling stage,maturity stage)was higher than that of spring maize.(3)The carbon flux of maize field is most affected by net radiation on the hourly scale.On the daily scale,spring maize is most affected by the vapor pressure deficit,and summer maize is most affected by the temperature.(4)SMPT-SB model has better simulation effect than the CROP-C model in the whole growth period of maize field,but the simulation effect in the day has its advantages and disadvantages: SMPT-SB model is more suitable for simulating the carbon source function of maize field at night;CROP-C model is more suitable for simulating the carbon sink function of maize fields during the day.