Agricultural Climate Yields Assessment Research In Three Provinces Of Northeast China

Northeast China is the most important major grain production area in our country and the agricultural climate yields assessment research there has strategic significance. Through analyzing the spatial distribution states and the temporal variation trends of climate elements, and the change characteristics of yields, further understanding of the average states of climate and the effects on the grain output in Northeast China were received. Methods of singular value decomposition and empirical orthogonal function were used to construct a comprehensive climate factor with the light, temperature and precipitation of each decade between April and September from 1980 to 2008, and then the economy-climate assessment models of the three provinces in Northeast China were built with yields, economic data and comprehensive climate factors. Good results were achieved when using these models to assess the yields, which laid foundation for the establishment and extension of agricultural climate yields assessment system in the future. The main results in the article would be presented as following:(1) The yields of the three provinces in Northeast China were affected by different climate conditions. Heilongjiang Province was limited by the heat condition, and Jilin Province was affected by both water and heat, the precipitation in the west was always less and the temperature in the east was always lower, and the climate of Liaoning Province was preferably only there was less precipitation in the west. Since 1980s, the temperature in the three provinces of Northeast China had increased significantly, which make the chilling damage disasters happen infrequently, while flood disasters happen in a decreasing trend and drought disasters happen in a increasing trend.(2) The spatial distribution states and the temporal variation trends of climate elements were different in Northeast China. During 1980 to 2008, the distribution of average temperature and more than 10℃effective accumulated temperature between April and September were decreasing from south to north and from west to east. There were three high value centers of low temperature days in June and August, which located in the northernmost and north of Heilongjiang Province and the east of Jilin Province. The first frost date in the south was earlier than in the north, and the length of growing season in the south was longer than in the north. The distribution of the total sunshine hours from April to September was decreasing from west to east, and the total precipitation from April to September was decreasing from east to west and from south to north. Since 1980s, the trend of average temperature and more than 10℃effective accumulated temperature had increased totally. The low temperature days in June had decreased dramatically while in August had changed little. The first frost date had postponed significantly, and the length of growing season had prolonged obviously. The total sunshine hours had changed little, and the total precipitation had been in a decreasing trend.(3) During 1980 and 2008, the main grain crops in Heilongjiang Province were maize, rice and bean while in Jilin and Liaoning Province were maize and rice. With the temperature increasing obviously, the chilling damage disaster was no longer the primary reason of the bad harvest, while high temperature and drought disasters were always causing the decline of production.(4) Economy-climate assessment models of the three provinces were built with yields, economic data and comprehensive climate factors which constructed by the climate data of each decade. The effect of comprehensive climate factors on yields in the three provinces was positive. The heat condition of the whole growing season in Heilongjiang Province was important especially between June and August, while in Jilin and Liaoning Province, the heat condition had major influence in early and late phase of growing season. Too much precipitation in August and September had negative effect on crops especially in the east of Jilin and Liaoning Province. The fertilizer per unit area had increased remarkably since 1980s which had played a significant role in the increasing of production. The effective irrigation areas had remained relatively stable which had less contribution to grain production.(5) Good results were received in the application of the economy-climate assessment models on agricultural climate yields assessment. The simulation values were close to the actual ones in most years which presented that the comprehensive climate factors and economy-climate assessment models could reflect the actual production situation. The yields assessment had also received good results which laid the foundation for the establishment and extension of the agricultural climate yields assessment system in the future.