| Wheat, accounting for22%cultivation areas and20%total yields of staple foods in China, and the winter wheat both accounting for90%cultivation and total yields of wheat.The winter wheat plays an important role in world food security. The temporal and spatial changes of winter wheat photothermal yields in the past few decades are important information needed to evaluate the impacts of global climate change on winter wheat production. The objective of this study is to quantify the temporal and spatial change trends of winter wheat photothermal yields and the impacts of temperature and radiation change so as to facilitate evaluating the impacts of climate change on winter wheat production in China. For this purpose, we first collected the experiment data (including development stages and yield) and the daily meteorological data (including solar radiation, minimum temperature and maximum temperature) at agro-meteorological experiment station in different cultivation areas to calibrate and validate (yield, and development stages) the GECROS model. The calibrated GECROS was used to simulate winter wheat photothermal yields with weather data of1961-2007from239sites in the region under study. And then the temporal and spatial change characters of photothermal yields and solar radiation, temperature during winter wheat growing season were analyzed with the help of Geographical Information System (GIS). At last, we further analyzed the effects of solar radiation and temperature changes on winter wheat photothermal yields in different cultivation areas. The main research results are as follows:1. GECROS calibration and validation:To obtain the suitable parameters of different cultivation areas, winter wheat cultivars Jimai No.30, Jimai No.20, Yangmai No.15, Chuanmai No.42and Mianyang No.26were selected for the representatives of the northern winter wheat area,the Huang-Huai winter wheat area, the middle, lower reaches of the yangtze China winter wheat area, the southwest winter wheat area and the south China winter wheat area, respectively. we first collected the experiment data (including development stages and yield) and the daily meteorological data (including solar radiation, minimum temperature and maximum temperature) at agro-meteorological experiment station in different cultivation areas to calibrate and validate (yield, and development stages) the GECROS model. The results validated by recorded flowering and maturing dates showed that the coefficient of determination(R2) are0.96and0.98, respectively, the root mean square error(RMSE) between simulated and observed data are4.3d and3.8d, respectively. The coefficient of determination (R) between simulated photo-thermal production and observed yields was0.81. By calibrating the model parameters, By calibrating the model parameters, GECROS simulated accurately development and Photo-thermal yields of the winter wheat, and can be applied to winter wheat production study in different areas.2. The temporal and spatial characters of potential production:winter wheat cultivars Jimai No.30, Jimai No.20, Yangmai No.15, Chuanmai No.42and Mianyang No.26were selected for the representatives of the northern winter wheat area, the Huang-Huai winter wheat area, the middle, lower reaches of the yangtze China winter wheat area, the southwest winter wheat area and the south China winter wheat area, respectively. The photo-thermal yields during1961-2007were simulated by GECROS with the data weather data from256sites in the region under study. The simulated results showed that the average winter wheat photo-thermal production during1961-2007varies from varies from10086.76kg-ha-1to10546.5kg-ha-1, by averagely10692.05kg-ha-1for the northern winter wheat; varies from10019.35kg-ha-1to13397.28kg-ha-1, by averagely11386.03kg-ha-1for the Huang-Huai winter wheat; varies from6290.13kg-ha-1to10432.67kg-ha-1, by averagely8291.32kg-ha-1for the middle and lower reaches of the yangtze China winter wheat; varies from5483.948kg-ha-1to13036.63kg-ha-1, by averagely8533.71kg-ha-1for the southwest winter wheat; varies from3902.36kg-ha-1to11604.8kg-ha-1, by averagely6167.78kg-ha-1for the south China winter wheat. The change trends of potential production during1961-2007in China varies from-8.77%·10a-1to4.3%·10a-1, by averagely1.74%·10a-1(141.5kg-ha-1·10a-1). The change trends of photo-thermal yields during1961-2007, varies from-3.0%·10a-1to0.094%·10a-1, by averagely-1.22%·10a-1for the northern winter wheat; varies from-2.41%·10a-1to3.32%·10a-1, by averagely-0.467%·10a-1for the Huang-Huai winter wheat; varies from-4.2%·10a-1to0.755%·10a-1, by averagely-1.48%·10a-1for the middle and lower reaches of the yangtze China winter wheat; varies from-5.92%·10a-1to0.494%·10a-1,by averagely-2.16%·10a-1for the southwest winter wheat; varies from-7.14%to-0.67%·10a-1, by averagely-3.46%·10a-1for the south China winter wheat.3. The impacts of photo-thermal changing on winter wheat photo-thermal in China: based on1961-2007, the effects of temperature increase1℃and solar radiation decrease10%on winter wheat photo-thermal yields in China were analyzed by GECROS. The results showed, during1961-2007, the average daily solar radiation change trends during the winter wheat growing season varies from-5.44%·10a-1to2.4%·10a-1, by averagely-1.67%·10a-1. As the solar radiation decrease10%, the change trends of photo-thermal yields varies from-5.34%to3.7%, by averagely-4.44%for the northern winter wheat; varies from-6.04%to1.86%, by averagely-4.15%for the Huang-Huai winter wheat; varies from-8.17%to-5.13%, by averagely-6.81%for the middle and lower reaches of the yangtze China winter wheat; varies from-10.1%to3.46%, by averagely-7.24%for the southwest winter wheat; varies from-10.3%to-4.39%, by averagely-8.02%for the south China winter wheat. During1961-2007, the average daily temperature change trends during the winter wheat growing season varies from-0.03to0.696℃·10a-1, by averagely0.31℃·10a-1. As temperature increase1℃, the change trends of photo-thermal yields varies from-4.65%to-0.827%, by averagely-1.96%for the northern winter wheat; varies from-7.87%to-1.17%, by averagely-5.3%for the Huang-Huai winter wheat; varies from-8.6%to-3.98%, by averagely-6.4%for the middle and lower reaches of the yangtze China winter wheat; varies from-11.7%to2.64%, by averagely-7.59%for the southwest winter wheat; varies from-10.4%to-6.1%, by averagely-7.5%for the south China winter wheat. Since the changes of photo-thermal resources in different areas are not synchronized. Therefore, by quantitatively calculating the contribution ratio of photo-thermal resources changes to the photo-thermal yields, we can analyze the effect of the hoto-thermal resources changes on it. During1961-2007, for the northern winter wheat and the Huang-Huai winter wheat, the temperature increasing and the solar radiation decreasing were both the main reasons for photo-themal yields decreasing, accounted for about50%sites in research.For the the yangtze China winter wheat, the southwest winter wheat and the south China winter wheat, the temperature increasing was the main reason for photo-themal yields decreasing, as the temperature and solar radiation change impacts ratio over1accounted for75%、69%and85%sites in research, respectively.Combining with the crop model GECROS, we simulated the winter wheat photothermal yields in the winter wheat cultivation areas and analyzed its temporal and spatial changing trends, and futher analyzed the effects of photothernal resources change on winter wheat photo-thermal yields. This work supports strongly to assess the effects of climate change on winter wheat production in China and to make measurements to adopt climate change. |
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