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Chinese Academy of Agricultural Sciences (2013)

Drought Risk Assessment of Winter Wheat and Summer Maize Rotation Planting Region in North China Plain

Hu Ya Nan

Titre : Drought Risk Assessment of Winter Wheat and Summer Maize Rotation Planting Region in North China Plain

Auteur : Hu Ya Nan

Grade : Doctoral Dissertation 2013

Université : Chinese Academy of Agricultural Sciences

North China plain is the main producing areas of agriculture and food production base in China.Winter wheat and summer maize rotation is major cropping pattern in the region. Combined withtheories and methods in meteorology, agriculture, disaster sciences in this study, it was designed forevaluate the agricultural drought disaster risk at1961 1990and2011 2050under A1B climaticscenario, taken the winter wheat summer maize rotation cropping pattern as the research object, andbased on the the agro-meteorological station data for1981to2009. It was also comprehensivelyutilizing the regional climate model and crop models as tools. The Palmer Drought Severity Index wasconducted for reflect the agricultural drought status at monthly and weekly scale in crop growth periods.Based on the results above, the risk assessment results reflected the drought disaster temporal andspatial distribution, and its changes, for the current yield level of winter wheat and summer maize. Themain results and conclusions of this study are as follows :(1) The northern boundary of winter wheat planting and summer maize potential growing areaswould be moving northward. The area of winter wheat summer and maize rotation planting patternwould be expanded at eastward and northward. Precipitation suitability in North China was significantlyimproved in2011 2050compared with1961 1990. Its precipitation condition would be moreconducive to the cultivation of wheat and maize.(2) For the past50years (1961 2010), the condition for wet or dry in North China has3-type ofdistribution patterns, which were―all consistency‖,―north-south reverse‖and―east-west reverse‖pattern. The analysis of time coefficients of three spatial distribution patterns showed that droughtdegree had an increasing trend since1980s.There had three distribution modes of drought for summer maize and winter wheat in1961 1990under A1B, which were―all consistency‖,―north-south reverse‖and―central reverse with north andsouth‖patterns. And its time coefficient showed that the―all consistency‖pattern was very typicalbefore1980s and the other two distribution modes were typical in1980s. For the next40years from2011 2050, the―all consistency‖drought distribution style would be mostly typical for both winterwheat and summer maize. And there would have a20consecutive years drought period at the overallrotation region for summer maize and winter wheat from2020s to the early of2040s.(3) The differences of maize drought occurrence frequency between1961 1990and2011 2050under A1B scenario, is larger than wheat. For the next40years, the frequency of drought will be bothincreasing for winter wheat and summer maize. The most significant increase in frequency range ofdrought occurrence area is larger than0.45for summer maize, but range from0.35to0.45for winterwheat. The area covered with drought frequency less than0.35will be significantly decreasednorthward in the next40years than baseline period for winter wheat and summer maize. It is larger ofsummer maize compared with winter wheat for the drought frequency at same time and same droughtdegree.(4) The effect of climate change on limited irrigating winter wheat would be positive, and96% area of the rotation planting region showed an increase in the average yield of in drought years. Theaverage yield of winter wheat in drought years in2011 2050, compared with the baseline period,showed that there’s little changes in production levels at the northern and southern, while had asignificantly increase in central region.95.1%of the region, the yield potential loss of winter wheatshowed downward trend in drought years, where the largest range of yield potential losses reductionwas located at Shandong Province. For the original rotation district,97.2%area of winter wheatpotential yield reduction was less than the value of the baseline period.In most part of the original rotation region, the average yield of rainfed summer maize in droughtyears in2011 2050would be lower than the values in baseline period. For the next40years, the yieldpotential losses of rainfed summer maize in drought years were higher than the baseline period, whichwas opposite to the decrease trend of winter wheat and the highest central region of yield potentiallosses were around Luoyang in Henan Province, Zibo and Weifang in Shandong Province. The ratio ofpotential yield reduction was greater than the value of the baseline period, in the92.4%of originalcropping rotation region, and the trend of winter wheat is just the opposite(5) Compared with baseline period, winter wheat drought risk overall rotation cropping area wasdecreasing in2011 2050. However, the very low risk, low risk and medium risk area of winter wheatwould be increase, while the high and very high risk area will be decrease. Drought risk for summermaize would mainly trend to increase in the next40years compared with the risk level for baselineperiod, especially that its high and very high risk area would be substantial increase, the low risk regionwould decrease sharply, and the risk of summer maize in new rotation region showed a high or veryhigh degree. Considering the whole rotation pattern, it was mainly midium drought risk both inreference prieod and future, but with a larger area in future than1961 1990.

Mots clés : North China Plain Winter wheat and summer maize rotation planting pattern Drought Drought disaster risk

Présentation (Dissertation topics)

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