中文摘要：

粮食生产功能是耕地最基本的功能,在半干旱区有着特殊的重要性。耕地的数量和质量变化直接影响粮食生产功能,而粮食生产又将对粮食的消费产生影响。本研究通过对西北半干旱区——宁夏自治区固原市多个时期耕地变化、粮食生产和消费变化的分析发现：在土地利用政策的驱动下,研究区耕地面积在不同时期发生了较大变动,保护生态和发展农业经济之间的矛盾在耕地上得到了集中体现;粮食产量大幅增长,主要贡献来自于粮食单产的提高,2005年时期的粮食单产水平提高到了1980年时期的3倍;在粮食产量增长的同时,粮食的种植结构中谷物种植比例降低,薯类比例增大,谷物品种减少;粮食供给逐渐变得充裕的同时,粮食消费结构由直接消费向间接消费转变。对固原市未来粮食生产和消费的预测显示,粮食增产速度高于消费增长速度,粮食供给能够充分满足当地消费需求。

英文摘要：

Cereal production is the most basic function of cropland, particularly important over semiarid areas. In general, most semiarid areas are economically underdeveloped and the standard of living of people is relative low. The government and public there place more emphasis on whether basic materials for living, particularly cereal, can be met Cereal production is primarily determined by the quantity and quality of cropland. Also, cereal production can affect cereal consumption because it determines cereal supply. In the present work, the authors investigated the mechanism of the effects of changes in cropland on grain production and consumption in Guyuan District, Ningxia Hui Autonomous Region, a typical semiarid area in China, since year 1978. It was found that in the past three decades, the area of cropland in Guyuan has been changed substantially and frequently arising from land use policies. The contradiction between ecological conservation and development of agricultural economy was therefore markedly reflected. Since year 2000, the project of grain for green （i.e. reconverting cropland and farmland to forests and grassland） has resulted in a drastic change in the area of cropland. Cereal yield has significantly increased, mainly resulting from an increase in yield per unit area, while a reduction in the area of cropland was meanwhile observed which contributed negatively to the increase in cereal yield. In period of 1980-2005, cereal yield per unit area has been tripled in the study area. It was also found that as cereal yield increased, the proportion of potato increased while both the proportion of grain and categories of cultivated grain decreased. Wheat and corn were two main grains. The structural of cereal consumption tended to shift from a kind of direct consumption before year 1995 to an indirect consumption later as the supply was gradually becoming ample. Urban residents consumed relatively less direct cereal but more indirect cereal than did rural residents. A transfer of population from rural