Risk Assessment Of Maize/Wheat/Rice Yield Losses In Mainland China

Climate change places additional stress on food security in China.The risk assessment of maize/wheat/rice yield losses is important for sustainable agricultural production and climate change impact assessment.In order to undertake cropping system adjustment in the future based on a more accurate and detailed risk assessment of yield losses,in this paper,an assessment was conducted using the yield and planting area time series data of maize/wheat/rice over the period 1981-2010 in main growing areas of mainland China.The data was used to get coefficient of variation,then divided into trending yield and meteorological yield by method of 5-year linear moving average method.Then meteorological yield was processed further to get the relative meteorological yield,in which the negative values were taken as the object to get the probability of yield reduction,risk index,comprehensive risk index.A new comprehensive yield loss risk index was established by combining the reduction rate,coefficient of variation,and probability of yield reduction after removing the area effect.The study showed the high-resolution spatial distribution of actual yield loss risks.A total of 823/874/707 main growing counties of maize/wheat/rice were divided into areas of lowest,low,moderate,high,and highest risk.The results were evaluated with the conclusions from the former researches,and with other data such as irrigation and drought.The main conclusions are as follow: 1.The trending yields of these three crops in most of the main growing counties increased evidently,which indicated that the socioeconomic conditions,such as the new crop varieties and improved management level,enhanced the grain crop yield greatly over China in the period from 1981 to 2010.2.The fluctuating range of meteorological yield of maize,wheat,rice was 41.6-1904.8 kg·ha^-1,34.3-980.8 kg·ha^-1 and 31.2-830.4 kg·ha^-1,respectively.The temporal average meteorological yield reduction of maize,wheat,rice was 39.8-1756.9 kg·ha^-1,0-671.4 kg·ha^-1,and 0-1430.7 kg·ha^-1,respectively.The meteorological yield reduction rate of maize,wheat,rice was 0-35.98%,0.89-33.5%,and 0-34.68%,respectively.The probability of yield reduction more than 15% of maize was higher in North China,while it of yield reduction less than 15% of wheat was higher in South China.3.The improved comprehensive yield loss risk index was established by combining the reduction rate,coefficient of variation,and probability of yield reduction after removing the area effect.The greater the improved comprehensive risk index was,the higher the risk of yield losses was.The comprehensive risk index of maize,wheat,rice was 0-0.311,0-0.023,and 0-0.019,respectively.High risk of maize production occurred in Heilongjiang and Jilin Provinces,the eastern part of Inner Mongolia,the eastern part of Gansu-Xinjiang,west of the Loess Plateau,and the western part of the Xinjiang Uygur Autonomous Region.Most counties in Northeast China were at high risk.High risk of wheat yield losses occurred in the Huanghuai Plain,Jianghuai Plain,and southern Shanxi to Jianghan Plain,northeastern part of Southwestern China.The high risk of yield losses of rice occurred discretely in the northeast and south of China.The risks of ri ce yield losses showed spatial variability obviously.