Mechanism Parameter Analysis Of Photosynthetic Module In BEPS Model And Simulation Application

Forest ecosystem is play an important role in global carbon cycle,forest ecosystems have absorbed about 20%of the world's emissions of carbon since the Industrial Revolution.BEPS(Boreal Ecosystem Productivity Simulator),a mechanism model driving by remote sensing data,has been widely used in estimating net primary productivity(NPP)of forest ecosystems in recent years,which can be used as an indicator of carbon fixation by vegetation.As a third-phase carbon cycle model,thanks to its strong mechanism,BEPS has the advantage of in coupling with climate,phenology and other models,can be used in studying of the impact of global climate change to carbon cycle.Although the BEPS model,which is based on describing the process of plant photosynthesis,can simulate the regional carbon budget well,when modeling with different mechanism parameters describing plant photosynthesis process,the model simulation accuracy will be greatly affected.In this study,we use the BEPS model,which take daily leaf area index(LAI)data and the meteorological data measured by the flux tower as the driving data,simulated the gross primary productivity(GPP)of Maoer Shan Ecological Station with different physiological parameters by using modified the model parameters according to the plant physiological processes,and then compared with the daily GPP measured by flux tower,the influence of different parameters in the model simulation and the applicability of these parameters under different external conditions were determined,and finally,analyzing the spatial and temporal changes of GPP and NPP in Heilongjiang Province in 2015 with using BEPS model under the most suitable parameters.Results show that:(1)the simulation using parameters(4,8)under the limit of supply of triphosphopyridine nucleotide(NADPH)is higher than true value,the simulation using parameters(4.5,10.5)under the limit of supply of adenosine triphosphate(ATP)is closest to true value(R2=0.84,RMSE=1.70 gC·m-2 d-1,Bias=1.38 gC m-2 d-1),the simulation using parameters(6,18)when PGA/DHAP shuttle occurs is unstable,is not suitable for simulating daily GPP;(2)universally,the simulation using parameters under the limit of supply ofNADPHis 6%higher than the simulation using parameters under the limit of supply of ATP,and the difference is up to 14.08%;(3)With light intensity enhancement and temperature rise,the model using the parameters limited by ATP supply is more suitable for simulating daily GPP.(4)For the forest GPP in Heilongjiang Province in 2015,the maximum value is 1669.19gC/(m2·a),the minimum value is 643.90gC/(m2·a),the average value is 1215.46gC/(m2.a).For the forest NPP in Heilongjiang Province in the same year,the maximum value is 975.11gC/(m2·a),the minimum value is 230.22gC/(m2-a),the average value is 735.03gC/(m2·a).In addition,the average value of GPP and NPP of agricultural land is 316.17gC/(m2.a)and 16.17gC/(m2.a)respectively.(5)According to spatio-temporal change analysis of GPP and NPP,plant growth season of Heilongjiang Province in 2015 relative lag,starting in April.The GPP and NPP of forest in Heilongjiang Province varied significantly with the seasons,gradually increasing from April to August and decreasing gradually from September to February.