The Possible Effects of Global Warming on Cropping Systems in China VI.Possible Effects of Future Climate Change on Northern Limits of Cropping System in China

【Objective】Climate change has become a global issue.The future climate will continue warming in China and this change will affect the national agricultural production to some extent.This paper aims at studying the possible effects of future climate change on the countrywide northern limits of cropping system,the northern limits of winter wheat,the stable-yield northern limits of rainfed winter wheat-summer maize rotation and the northern limits of tropical crops. 【Method】According to the climatic zoning indices of national cropping system,the northern limits indices of winter wheat,the northern limits indices of stable-yield in rainfed winter wheat-summer maize rotation and of tropical crops,the classical calculation methods of agro-meteorological indicators were adopted to analyze the changes of all northern limits in the coming 30 years(2011-2040) as well as in the middle of this century(2041-2050) compared with that during 1950s-1980. 【Result】Compared with the situation during 1950s-1980,the northern limits of two-cropping system and three-cropping system during 2011-2040 and 2041-2050 would both move northward in different degree,as to the northern limits of two-cropping system,the maximum spatial displacement would occur in Shaanxi province and Liaoning province,while the northward move during 2041-2050 would be the most obvious;as to the northern limits of the three-cropping system,the maximum spatial displacement would occur in the region including Yunnan province,Guizhou province,Hubei province,Anhui province,Jiangsu province and Zhejiang province,while the northward move during 2041-2050 would be the most obvious,too.Without considering the variety change and socio-economic factors,the regional cropping system would change from one-cropping system to two-cropping system,or from two-cropping system to three-cropping system,which would lead to the increase of annual grain yield per hectare in different degrees.Compared with the situation during 1950s-1980,the northern limits of winter wheat during 2011-2040 and 2041-2050 in Liaoning Province,Gansu Province,Ningxia Hui Autonomous Region would move northward in different degrees,while the planting limits of winter wheat in Qinghai Province would expand westward significantly.Without considering the effect of other factors,the increase of regional grain yield per hectare would be expected by planting winter wheat instead of spring wheat.The safety northern limits of tropical crops in Guangxi Zhuang Autonomous Region and Guangdong Province would move northward more significantly.Yet the increase of future precipitation would make the stable-yield northern limits of rainfed winter wheat-summer maize rotation move northwestward in most regions. 【Conclusion】By 2011-2040 and 2041-2050,climate change would cause northward move of northern limits of national cropping system in different degrees,northward move together with western expansion of northern limits of winter wheat,and northward move of northern limits of tropical crops.Yet the increase of future precipitation would make the stable-yield northern limits of rainfed winter wheat-summer maize rotation move northwestward in most regions.