TEMPORAL AND SPATIAL VARIATION OF CLIMATIC POTENTIAL PRODUCTIVITY FOR GRAIN CROPS IN EASTERN CHINA WITHIN FORTY YEARS

Temperature and precipitation patterns varied in China corresponding to global warming due to increase of CO 2 concentration in the atmosphere. To make policy for food security of China, it is necessary to evaluate the potential change of grain crop production in both temporal and spatial scale under the heat and rainfall variations in Eastern China, where is the most important grain production area in China. Weather data from 1955～1990 for 129 stations were collected to calculate yearly and average climatic potential productivity of grain crops (both summer and fall crops) and their temporal and spatial variations by using statistical analysis of the empirical orthogonal function (EOF). The results showed that it was not enough to assess the climatic resources by using average climatic potential productivity, because of annual variations of heat and rainfall and their combinations. The productivity in a high year was 2 8 times of that for summer grain crops and 7 4 times of that for fall grain crops in a low year. The global warming trend had little effects on spatial distribution and temporal trend of summer grain crop productivity in Eastern China. Summer grain crop productivity fluctuated due to the unstable monsoon climate. For fall grain crop productivity, the global warming trend had effect on their spatial distribution and temporal change. There was reverse spatial distribution of productivity variation between middle and lower reaches of the Changjiang River and other regions in Eastern China. Temporal change trend was obvious. During 1955～1990, the climatic potential productivity of fall grain crops was increasing in the middle and lower reaches of the Changjiang River, but was decreasing in other regions.