Impact Assessment of Cultivated Land Change upon Gr ain Productive Capacity in Nor theast China
东北地区耕地变化对粮食生产能力的影响评价

It is of great significance to research the changing patterns of current regional cultivated land and explore its impact on grain productivity. "3S" technology can not only improve precision, speed and efficiency of data collection, but also obtain and manage various kinds of agricultural resource information with spatial attributes effectively, and monitor and assess the cultivated land dynamic change. This research is innovative in such aspects as research content, method and so on. Firstly, taking Northeast China as a study area, with the help of "3S" technology and on the basis of spatial and temporal land resource data, agricultural statistics data and considering the natural and socio-economic factors, this paper analyzed the impact of cultivated land change on the grain production capacity within this region in terms of cultivated land quantity, cultivated land quality, crop structure etc. Secondly, since the soil nutrient data obtained from field survey in 2005 differ greatly from the data obtained at the time of the second soil survey in the 1980s on the aspect of sample position, quantity, time and soil analytical method, this paper did not carry out comparative research with the cultivated land quality of the period of the second soil survey, but analyzed the spatial distribution of the change of the cultivated land quality caused by the change of cultivated land quantity. Thirdly, considering cultivated land quality is the comprehensive reflection of different properties of cultivated land, the elements of cultivated land quality include the natural factors and social-economic factors mainly. And the natural resources, cultural structure and social-economic conditions among different regions may vary greatly, thus the natural and social-economic factors will exert different effects on grain production in different regions, and this proves that it is important to manage cultivated land resources based on regionalization. In recent years, the peasants have increased the input amount on the cultivated land, such as fertilizer and mulch film, which resulted in different effects on cultivated land quality in Northeast China. Under the above-mentioned background, this paper analyzed cultivated land quality information in the concerned region. The method was to explore natural quality grading and utilizing quality grading on cultivated land respectively through natural quality grading and utilizing quality grading indicator systems. And then we divided the whole region into high-yield cultivated land, medium-yield cultivated land and low-yield cultivated land based on per unit area grain yield, and the correlation was analyzed between natural quality grading of land and per unit area grain yield as well as between utilizing quality grading of land and grain yield per unit area through GIS method. In a word, this paper can provide some help to sustainable utilization and management of cultivated land resource in the study and offer useful ref