Simulation Of The Effects Of The Combination Of Elevated Atmosphere CO₂ And Temperature On Rice Growth And Development

Climate change is mainly characterized by atmospheric CO₂ concentration elevation and temperature increase,which affects crop productivity through crop growth and development?eg,growth rate,leaf photosynthetic parameters,specific leaf area and partition coefficient,etc.?.Therefore,climate change will affect crop production and food security on the long run.Crop model is a useful tool for studying the impact of future climate change on crop yield.The elevated CO₂ concentration will cause the leaf photosynthetic adaptation of C3 crop,and the increased temperature will change the optimum temperature of photosynthesis.However,the existing crop growth model does not consider the adaptive response of crop growth process under elevated CO₂ concentration and increased temperature.FACE?free air CO₂ enrichment?experiments under field conditions including increased air temperature is the effective way to explore the crop responses to elevated CO₂ and increased temperature.Four treatments with three replications for each treatment were designed in the experiments:one with target free air CO₂ concentration up to 500ppm?C?,one with canopy temperature increased by 1.5-2??T?,and one with combined of free air CO₂ enrichment and increased temperature?CT?,one untreated plot with ambient condition as control?CK?,to analyse the rice to elevated CO₂ and increased temperature in T-FACE system established in Changshu Municipality,Jiangsu,China during 2013-2014.First,the rice growth model ORYZA2000 was calibrated and validated based on the data obtained from the field control experiment in 2013 and 2014.On this basis,the physiological and ecological data obtained by the experimental study were combined with the ORYZA2000 model simulation analysis.Under elevated CO₂ concentration and increased temperature,the effects of ORYZA2000 model on the simulation of rice development,leaf leaf area and photosynthetic parameters on rice aboveground total dry weight,and partition coefficient on LAI and yield simulation are studied.The main research results were as follows:?1?ORYZA2000 can simulate the development of rice well under elevated CO₂ and increased temperature.Under elevated CO₂ concentration,increased temperature,and combination of elevated CO₂ and increased temperature,the simulated values were compared with the observed values from sowing to heading:shortened by 0 d,delayed by 3,delayed by 2-6 d,the simulated values were compared with the observed values from heading to maturity:delayed by 1-2d,shortened by 2-3d,shortened by 3d,the simulated value of the whole growth period is compared with the observed value:delay 1-2d,delay 1d,delay 3d.?2?ORYZA2000 will overestimate the aboveground biomass under elevated CO₂ and increased temperature,which is mainly due to the larger specific leaf area?SLA?and photosynthetic parameters?Amax,??of the model.Before the SLA is calibrated,the simulated value of the aboveground biomass of the harvest period will be overestimated 14%,16%and 22%than the observed value under elevated CO₂,increased temperature and combination of elevated CO₂ and increased temperature condition.Before the photosynthetic parameters is calibrated,the simulated value of the aboveground biomass of the harvest period will be overestimated 14%,31%and 33%than the observed value under elevated CO₂,increased temperature and combination of elevated CO₂ and increased temperature.After the calibration of the LAI and photosynthetic parameters,the simulated value of the aboveground biomass of the harvest period is 7%,9%and 14%higher than the observed value,respectively,under elevated CO₂,increased temperature and combination of elevated CO₂ and increased temperature.?3?ORYZA2000 will overestimate the leaf area index?LAI?and yield under elevated CO₂ and increased temperature,which is mainly due to the fact that the model does not consider the effect of elevated CO₂ and increased temperature on rice partition coefficient.Before the partition coefficient is calibrated,the simulated value of LAI will be overestimated 7%,3%and 7%than the observations,the simulated value of yield will be overestimated 7%,8%and 10%than the observed value under elevated CO₂,at maturity increased temperature and combination of elevated CO₂ and increased temperature condition.After the calibration of the partition coefficient,the simulated value of LAI will be underestimated 5%,underestimated 1%and overestimated 2%than the observed value,the simulated value of yield will be overestimated 5%,4%and 3%than the observed value at maturity under elevated CO₂,increased temperature and combination of elevated CO₂ and increased temperature condition.This study provides a reference for further improvement of other crop growth simulation models to accurately assess the impact of climate change on crops.