三江平原过去50年耕地动态变化及其驱动力分析

在遥感和地理信息系统技术支持下,本文对三江平原建国以来耕地变化方式及与其它土地利用类型的转化进行了定量研究。结果表明,在过去50多年里,三江平原耕地面积发生了显著变化。在建国初期的1954年,耕地面积为17133.81 km2,所占比重仅为15.91%;2005年耕地为55688.45 km2,面积比为51.17%,耕地面积净增加了38554.64 km2,年均耕地增加面积为755.97 km2。通过耕地与其它土地利用类型的转化分析表明,湿地开垦对耕地的增加贡献最大,其次为林地与草地。通过垦殖指数及其变化模型分析表明,三江平原不同历史时期耕地面积的变化速率存在很大的时空差异;区域本身人口急剧增加、国家有计划的农垦移民、农业机械化水平提高是导致本区耕地面积不断增加的主要原因;三江平原区域自然条件,尤其是地势、地貌与土壤条件同样影响着三江平原耕地面积的变化。

Analysis of Cultivated Land Dynamics in the Past 50 Years in Sanjiang Plain and Its Driving Forces

With the combination of GIS technology and remotely sensed data,cultivated land changing trend in regional scale can be easily traced and inventoried in time.Six periods of land use spatial data bases were established with remote sensing imagery data and scanned topographic map in ARC/Info 9.0 software.The cultivated land changing feature and mutual conversion with other land use were analyzed quantitatively.It was found that cultivated land drastically changed in the past 50 years.The cultivated land was only 17 133.8 km2 in 1954,the proportion of cultivated land only amounted to 15.91% in Sanjiang Plain;while the cultivated land amounted to 51.17% in 2005,which was 55 688.45 km2 in total area.Cultivated land increased 38 554.64 km2 in the whole study periods,and the average increased area is 755.97 km2 per year.By mutual conversion analysis of cultivated land and other land use,it was found that reclamation of wetland was the main contributor for cultivated land increase,and forest and grassland converted to cultivated land was another reason for its increasing.Cultivated ratio and changing rate were applied to analysis the cropland dynamics characteristics in the past 50 years,it was found that cultivated land changing area and rate showed significant variation during different study periods.Population increasing,large amount of immigrant swarming into Sanjiang Plain as result of national policy,enhanced by agricultural technology development was the main reason for the cultivated land increase in the whole study periods.Still,it should be notice that natural conditions also played an important role in the cultivated land changing trend,especially,topographic and soil environment cast an impact on cultivated land changing location,and its pattern as well.