| Rice, accounting for33%cultivation areas and39%total yields of staple foods in China, plays an important role in world food security. The temporal and spatial changes of rice photothermal yields in the past few decades are important information needed to evaluate the impacts of global climate change on rice production. The objective of this study is to quantify the temporal and spatial change trends of rice photothermal yields and the impacts of temperature and radiation change so as to facilitate evaluating the impacts of climate change on rice 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 (phenological development parameters and partitioning tables) and validate (yield, and development stages) the ORYZA2000model. The calibrated ORYZA2000was used to simulate rice 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 rice 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 rice photothermal yields in different cultivation areas. The main research results are as follows:1. ORYZA2000calibration and validation:To obtain the suitable parameters of different cultivation areas, rice (Oryza sativa L.) cultivars Linzhong No.5, Shanyou63, D You63, Guizhao No.2were selected for the representatives of single rice in the Northeast, the Central, the Southwest in China and double rice in South China, respectively. The experiment and meteorological data collected at Wuchang in Heilongjiang province (1993-1996), Xuzhou in Jiangsu province (1990-1992,1995-1996), Hanyuan in Sichuang province, Gaoyao in Guangdong province (1982-1986,1997-2002) agro-meteorological experiment stations were used to calibrate and validate the crop model ORYZA2000. Photo-thermal production were validated used the experimental data of Shanyou63(as-control) in four stations for new variety test (i.e. Yancheng in Jiangsu province, Hefei in Anhui province, Yichang in Hubei province, Huaihua in Herman province) during2004-2005. The results validated by recorded flowering and maturing dates showed that the coefficient of determination (R2) are0.88and0.87, respectively, the root mean square error (RMSE) between simulated and observed data are2.8d and2.2d, respectively. The R2between simulated photo-thermal production and observed yields was0.74. By calibrating the model parameters, ORYZA2000simulated accurately development yields in different areas and can be applied to rice production study in different areas.2. The temporal and spatial characters of potential production:rice (Oryza sativa L.) cultivars Linzhong No.5, Shanyou63, Dyou63and Guizhao No.2were selected for the representatives of single rice in the Northeast, the Central, the Southwest in China and double rice in South China, respectively. The photo-thermal yields during1961-2007were simulated by ORYZA2000with the data weather data from239sites in the region under study. The simulated results showed that the rice photo-thermal yields during1961-2007varies from14467kg·ha-1to18734kg·ha-1, by averagely16609kg·ha-1for the northeastern single rice;varies from13930kg·ha-1to19380kg·ha-1, by averagely15545kg·ha-1for the Central single rice; varies from13535kg·ha-1to20982kg·h-1, by averagely16446kg·ha-1for the Southwestern single rice; varies from11318kg·ha-1to14868kg·ha-1, by averagely13130kg·ha-1for the Southern early rice; varies from11561kg·ha-1to14316kg·ha-1, by averagely12760kg·ha-1for the Southern later rice. The change trends of potential production during1961-2007varies from-3.8%·10a-1to-0.2%·10a-1, by averagely-1.9%·10a-1(-315kg·ha-1·10a-1) for the northeastern single rice; varies from-4.1%·10a-1to-0.2%·10a-1kg·ha-1, by averagely-2.4%·10a-1(-366kg·ha-1·10a-1) for the Central single rice; varies from-6.2%·10a-1to0.3%·10a-1, by averagely-1.9%·10-1(-326kg·ha-1·10a-1)for the Southwestern single rice; varies from-4.8%·10a-1to0.6%·10a-1, by averagely-1.9%·10a-1(-244kg·ha-1·10a-1) for the Southern early rice; varies from-4.2%·10a-1to0.3%·10a-1, by averagely-1.9%·10a-1(-238kg·ha-1·10a-1) for the Southern later rice.3.The impacts of photo-thermal changing on rice rice photo-thermal in China:based on1961-2007, the effects of temperature increase1℃and solar radiation decrease10%on rice photo-thermal yields in China were analyzed by ORYZA2000. The results showed, during1961-2007, the average daily solar radiation change trends during the rice growing season varies from-6.5to2.0%·10a-1, by averagely-2.3%10a-1(-0.36MJ·m-2·10a-1). As the solar radiation decrease10%, the change trends of photo-thermal yields varies from-5.2%to-3.0%, by averagely-4.0%(-672kg·ha-1) for the northeastern single rice; varies from-6.2%to-3.3%, by averagely-4.4%(-675kg·ha-1)for the Central single rice; varies from-6.6%to-2.3%, by averagely-5.6%(-915kg·ha-1) for the Southwestern single rice; varies from-6.3%to-3.5%, by averagely-4.9%(-637kg·ha-1) for the Southern early rice; varies from-6.1%to-2.2%, by averagely-4.3%(-549kg·ha-1) for the Southern later rice. During1961-2007, the average daily temperature change trends during the rice growing season varies from-0.14to0.69℃·10a-1, by averagely0.13℃·10a-1. As temperature increase1℃, the change trends of photo-thermal yields varies from-6.5%to-3.3%, by averagely-4.5%(-761kg·ha-1) for the northeastern single rice; varies from-5.9%to-2.9%, by averagely-4.3%(-660kg·ha-1)for the Central single rice; varies from-8.2%to-2.8%, by averagely-5.8%(-975kg·ha-1) for the Southwestern single rice; varies from-6.5%to-3.6%, by averagely-4.6%(-606kg·ha-1)) for the Southern early rice; variesjfrom-6.1%to-2.4%, by averagely-4.1%(-533kg·ha-1) for the Southern later rice. For Northeast single rice, the temperature increase was the main reason for photo-thermal yields decrease as the temperature and solar radiation change impacts ratio over1accounted for62%sites in research. For the Central single rice, the Southwestern single rice, the South early and later rice, the solar radiation decrease was the main reason for photo-thermal yields decrease as the temperature and solar radiation change impacts ratio less1accounted for91%,62%,70%and89%sites in research, respectively.Combining with the crop model ORYZA2000, we simulated the rice photothermal yields in the main rice cultivation areas and analyzed its temporal and spatial changing trends, and futher analyzed the effects of photothernal resources change on rice photo-thermal yields. This work supports strongly to assess the effects of climate change on rice production in China and to make measurements to adopt climate change. |
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