Study Of Canopy Photosynthesis And Evapotranspiration Coupled Model In The Agroecosystem

It is one of the centricity problems of carbon cycle and water cycle on terra to estimate agroecbsystem photosynthesis and evapotranspiration accurately. At present, there are many agroecosystem models in home, with insufficient mechanism and representation, simulating photosynthesis and evapotranspiration separately, and a few photosynthesis and evapotranspiration coupled models with insufficient accuracy for not considered the processes relating to the carbon dioxide and water vapor flux transfer in field detailed.So it is the purpose of this thesis to establish an agroecosystem canopy photosynthesis and evapotranspiration model with strong mechanism and high accuracy.(1) In the thesis, a canopy photosynthesis and evapotranspiration coupled model in the agroecosystem has been developed. The model consists of three modules, a canopy evapotranspiration model, a canopy photosynthesis model and a water and heat transfer in the soil model. The sub-models in every module with strong mechanism are not too complicated. Thus, the model can be applied into different areas and the accuracy of the model is high. We integrate the sub-models systematically and organically to develop a new model.(2) Validating the model with some data measured by eddy covariance method. The time step of the model is ten minutes. The main output results of the model are CO2 flux, sensible heat flux, latent heat flux and net radiation. The analysis between simulated value and observed value indicates that there is a marked correlation between them and their shapes are very accordant with error less than 10%.(3) We analyze the sensitivity of main parameters of the model. In daytime, the most sensitive parameter of the COa flux in canopy is the intrinsic quantum efficiency. The sensitivity of the convexity of photosynthesis-light response curve, COa compensation point, the wilt water potential and leaf area index are also strong. In the nighttime, the sensitive parameters of the CO2 flux in canopy are the Rubisco catalytic capacity of at optimal temperature and the dark respiration parameter. The sensitive parameters of canopy transpiration are the wilt water potential, the stomata conductance parameter, the albedo of leaves to the infrared radiation, and the convexity of photosynthesis-light response curve. The sensitive parameter of soil evaporation is only soil resistance parameter.(4) Analyzed the respons of the model to environmental factors.