1990-2013年东北地区耕地时空变化遥感分析

Spatio-temporal dynamics analysis of cropland in Northeast China during 1990-2013 based on remote sensing

为揭示1990-2013年东北地区耕地变化规律,以Landsat TM/ETM+/OLI遥感影像为数据源,采用面向对象与目视解译相结合的分类方法,提取东北地区1990年、2000年和2013年耕地信息,辅以气候、地形、社会经济等数据,分析耕地时空变化特征及其驱动因素。结果表明:面向对象分类与目视解译相结合的方法能够快速、准确地完成耕地空间分布信息提取,总体分类精度达93%以上;2013年东北地区现有耕地4.17×105 km2,占东北地区土地总面积的33.51%,其中旱田比例为86.24%;1990-2013年耕地总量增加,2000-2013年比1990-2000年耕地增加速度减小,空间上,耕地呈现南减北增的趋势,新增耕地重心逐渐北移,建设用地侵占耕地速度加快,以省会城市为中心,向东北部蔓延;对湿地、林地、草地开垦减弱,对裸地和海面的农业开发增强,退耕还湿、还草、还林效果明显,耕地变化活跃区处于年降水量在500~700 mm、年均气温在2~4℃、坡度小于3°、高程小于200 m的地理环境中;旱田改为水田规模扩大,旱田质心变化不显著,水田质心向东北移207.41 km。23 a间,虽然气候变化对东北地区耕地变化有一定影响,但政策调控、经济发展、科技进步、人口增长、城市扩张等人文因素仍然是耕地变化和时空分异特征的主要驱动因素。农业发展转型、提高单位面积产量和劳动生产效率,将是未来东北地区耕地发展的必由之路。

The Northeast region is one of the most important agricultural production bases in China. To reveal the change rules of cropland in Northeast China, based on Landsat TM/ETM+/OLI images, combining object-based classification and manual interpretation, the information of cropland in 1990, 2000 and 2013 was extracted. Combining the results of classification and other relevant data such as climate, terrain and economy, the characteristics of spatio-temporal pattern and its driving factors in Northeast China were analyzed. The results showed that: combining object-based classification and manual interpretation could access cropland information quickly and accurately, and the classification accuracy was above 93%. The total area of cropland in Northeast China was 41.66 million hectares in 2013, which was 33.51% of total area in Northeast China, including 13.76% of paddy land and 86.24% of dry land. In the 4 provinces, the cropland in Heilongjiang was the most. From 1990 to 2013, the total area of cropland in Northeast China increased by 2.25×104 km2, including 2.21×104 km2 during 1990-2000 and 369.51 km2 during 2000-2013, and the quick change of cropland decreased. The increased cropland was derived mainly from reclaiming wetland of 1.18×104 km2(49.40%) during 1990-2000 and 4438.62 km2(67.77%) during 2000-2013. Though the amount was a few, it was an important characteristic that the cropland increased from sea surface reclamation. The decreased cropland was transformed mainly into build-up land and wetland, including 795.89 km2(39.70%) and 649.27 km2(32.39%) respectively during 1990-2000 and 2098.85 km2(32.79%) and 2028.86 km2(31.70%) respectively during 2000-2013. The cropland occupied by build-up land was mainly distributed around provincial capitals such as Harbin, Changchun and Shenyang and in lower reach of Liaohe River Plain, and the cropland transformed into wetland was mainly distributed in Sanjiang Plain and Songnen Plain. The reclamation from wetland, woodland and grassland receded, and the reclamation from bare land and sea enhanced. The effects of the 'Grain for Green Project' were significant. Comparing 1990-2000 and 2000-2013, dry land increased at first and then decreased, and paddy land increased continuously. The increased paddy land was derived mainly from dry land. The proportion of dry land transformed into paddy land and paddy land transformed into dry land was 6:1 during 1990-2000 and 7.7: 1 during 2000-2013. Planting pattern change was another important feature. The area-weighted centroid of paddy land generally moved northeastward by 207.41 km, and the area-weighted centroid of dry land changed non-significantly. The cropland across China indicated a significant variation in spatio-temporal characteristics in the past 23 years. The amount of cropland decreased in the south and increased in the north. The barycenter of newly increased cropland moved north. The regions with significant cropland change occupied those conditions which were the annual precipitation from 500 to 700 mm, the mean annual temperature between 2℃ and 4℃, the slope less than 3°, and the elevation less than 200 m. During the 23 years, although climate change impacted the change in cropland, the factors in policy regulation, economic development, scientific and technological progress, population growth, urban sprawl and other human factors played the main roles in the cropland change, which impacted the spatio-temporal characteristics, and policy regulation was the leading factor. The road that the pattern of agricultural development transforms, and the labor productivity and the yield per unit area increase will be the only road to the development of cropland in Northeast China.