Modelling The Impacts Of Rising Temperature On Maize Growth,Development And Potential Growing Season

Extreme high temperature events occurred more frequently in the past decades and are projected to increase in magnitude,duration,and frequency.Climate warming has had significant impacts on agricultural production.Accurately assessing the impacts of climate warming on crop yield is essential in developing effective adaptation strategies for agriculture adapting to climate change.Crop growth models have been recognized effective tools to evaluate the impacts of future climate change on crop production and develop suitable adaptation options.However,large differences existed between different maize phenology models in simulating the impacts of temperature on growth and development of maize especially under high temperature due to different datasets and purposes when these models were developed.The modules of phenology and photosynthesis are key modules in the crop growth models.Accurately modelling the responses of growth and development of maize to temperature is helpful to improve maize yield simulation accuracy and decrease the uncertainties in assessing the impact of future climate change on maize production with crop growth models.Crop phenology affects the the partitioning and timing of assimilates to different organs and is also an important index in assessing climate change imapcts.Selecting maize cultivars with longer growing period is one of the most effective adaptation measures to climate warming.However,it is not clear whether the local maize cultivars have fully utilized the potential growth season and whether prolonging growing period of maize can increase potential yield of maize.In this study,the uncertainty in simulated maize phenology by six popular maize phenology models under future climate change scenarios was investigated based on observed development data of maize at typical agro-meteorological observational stations in China's northeast-southwest maize belt.Subsequently,we combined the data reported in literature and our controlled-temperature experiment to derive the temperature response functions of phenological development and biomass accumulation of maize crop based on the Wang-Engel function and compared them with those adopted in two mostly used maize growth models APSIM-Maize and CERES-Maize.Based on long-term datasets of maize phenology observed by agricultural meteorological stations,the utilization rate of maize potential growth season and the impacts of extending maize growing period on simulated maize yield by APSIM model were investigated under the climate change background in China's Maize Belt.The main study results were as following:(1)Six popular maize phenology models could reach acceptable precision(NRMSE<8%for all the six models)after the calibration based on observed phenology data of maize under current climate.Under future climate change scenarios,increased temperature would result in advance of simulated silting and maturing dates by all the models except the delay of simulated phenology by Beta model in the North China Plain.The uncertainty in simulated maize phenolgy between the models increased with rising temperature,especially in phenology of summer maize in the North China Plain.The uncertainty between models in simulated maize phenology increased with the coefficient of fluctuation from 3.2%under the baseline climate(1970-1999)to 6.3%under RCP4.5 and 7.4%under RCP8.5 in 2030s and 8.9%under RCP4.5 and 14.5%under RCP8.5 in 2080s for the simulated silking date,and from 4.2%under the baseline to 7.0%under RCP4.5 and 7.7%under RCP8.5 in 2030s and 10.2%under RCP4.5 and 16.7%under RCP8.5 in 2080s for the simulated maturity date in North China Plain.(2)A curvilinear response with cardinal temperatures of 5 ?(base),30 ?(optimum),and 41 ?(maximum)best describes the maize developmental response to temperature.For radiation use efficiency(RUE-biomass growth per unit intercepted radiation)of maize,the corresponding cardinal temperatures are likely to be 2 ?,24 ?,and 38 ? respectively.All the cardinal temperatures are lower than what are used in current APSIM model.Replacing the default temperature responses with the newly derived ones led to contrasting differences in simulated flowering and maturity time across China' s Maize Belt,while the differences in simulated maize yield were relatively smaller.This implies the importance to use the correct temperature response in maize growth modelling so that the genotype by environment interactions in response to rising temperature can be correctly captured.(3)Under the current cropping system,the utilization rate of the potential growing season increased from 86.1%in 1980s to 90.3%in 2000s in the North China Plain(NCP),from 82.6%in 1980s to 86.4%in 2000s in the Northeast China(NEC),but decreased from 65.2%in 1980s to 62.5%in 2000s in the Northwest China(NWC).The utilization rate of maize potential growing season was only 42.1%to 44.9%without the limitation of double cropping system.The ratio of accumulated pre-flowering effective thermal time to accumulated post-flowering effective thermal time was 1.5 to 1.7 before the 2000s and decreased to 1.0-1.6 after the 2000s,which suggested new released maize cultivars had longer grain-filling period.Under current climate condition,maize growing season could be extended about 14 days to achieve the highest potential yield.However,extending maize growing season could cause large yield variation under rainfed conditions in the Northwest China.