| With the concentration of the rice and winter wheat in the Middle and Lower Yangtze River,the 0.5°×0.5° grid daily meteorological data output by the scenario of RCP of BCCCSM1-1(Beijing Climate Center Climate System Model version1-1)over the middle and lower Yangtze River during from 2021-2050 was selected to downscale the model data to 62 national weather stations by the bilinear interpolation method.Subsequently,the RCPs scenarios data during 2021-2050 was corrected using variance correction method from nonlinear equation of the simulated and observed data over the reference period of 1961-1990.the spatio-temporal characteristics of mean temperature,precipitation and solar radiation were investigated under high-end path Representative Concentration Pathway RCP 8.5 and stable path RCP4.5 scenarios.Meanwhile,the spatial and temporal characteristics of potential climatic productivity over the next 30 years were estimated using experience model(mechanism method)and crop-based model(DSSAT),and the sequential driving factors of the dynamics of potential climatic productivity were determined.The main results were as follows:(1)The simulation of RCP scenario output data was detected to be satisfactory.The annual mean temperature and annual solar radiation would significantly increase over the middle and lower Yangtze River,whereas the amplitude of the temperature increase gradually reduced overall from south to north under the two scenarios.The trend of temperature increased in four selected seasons with the higher change rate in summer.Accordingly,for the RCP 8.5 scenario,the increasing rates of spring and winter were found to be higher than that in the RCP 4.5 scenario.Under the RCP 8.5 scenario,the highest value was depicted in the central of research area for annual mean temperature,and the warming rate was found to be higher in spring and summer than other seasons and the most of station was found no significance in winter.While for the RCP 4.5 scenario,the annual mean temperature was detected to reduce gradually from north to south.Thereby,the increasing rate was found to be higher significantly in summer than that in winter.The spatial distribution of annual solar radiation in the Middle and Lower Yangtze River during 2021-2050 shows higher in middle parts of the studied region,while lower in the south part of jiangsu province,middle east of anhui province,and some parts of hubei and hunan province.In the perspective of seasonal variation,solar radiation decreases in the order of spring,summer,autumn,and winter.However,precipitation shows insignificantly decreasing trend for most part of the studied regional during 2021~2050,with the seasonal pattern of lowest in winter and highest in summer.(2)The estimated potential climatic productivity of wheat tended to increase from the central to the southern areas,whereas the potential productivity of rice exhibited the opposite tendency,decreasing from north to south during the baseline period.In the RCP 4.5 scenario,the potential climatic productivity of rice and winter wheat exhibited strong regional characteristics,increasing by 3500–5000 kg/hm2 and 5000–6050 kg/hm2,respectively.In the RCP 8.5 scenario,the overall potential climatic productivity of rice and winter wheat exhibited significantly increasing amplitudes of 4000–6000 kg/hm2 and 11000 kg/hm2,respectively,from those under the baseline scenario.The potential climatic productivity of winter wheat tended to decrease gradually from east to west in the middle and lower reaches of the Yangtze River.The potential climatic productivity of crops in the plain was greater than that in other areas at the same latitude.During the growth period,accumulated temperature was the most important factor affecting plant growth,followed by solar radiation.Accordingly,sufficient and harmonious climatic resources are thought to be the essential conditions for obtaining high potential climatic productivity.(3)The accumulative temperature(over 10℃),precipitation and total solar radiation of the growing period of winter wheat during 2021-2050 compared with baseline climatic condition.The precipitation fluctuation was relatively large with obvious regional differences and insignificant change rate.The total solar radiation in the two RCP scenarios was lower than the baseline,while the rate decreases with the increase of the year.The flowering and maturing stages of winter wheat were delayed(RCP 8.5> RCP 4.5),and the days from flowering to maturity decreased.Those results indicated that winter wheat yield increased gradually with the increase of accumulated temperature,which in turn decreased as a certain threshold was exceeded.What’s more,the increase or decrease of other climatic factors could not compensate for the negative effects of low accumulated temperatures.When the temperature was higher,flowering and maturity would be delayed,which subsequently prolonged vegetative growth,blocked reproductive growth,resulted in too much tiller,and reduced the spike rate,thereby causing lower yield.The rice potential yield during future projection shows the tendency of 2030s<2040s<2050s,however it is lower than that in the baseline period.And the yield decreasing rates was higher for RCP8.5 scenario when compared to RCP4.5.Analysis demonstrated that,due to the negative impact of heat stress on rice photosynthetic rates and respiration rate,the yield reduction rates has a positive correlation with the accumulative temperature,and maximum temperature,which indicates that the increasing temperature during the rice growing period is the limiting factor for rice production in the Middle and Lower Yangtze River. |
