美洲耕地利用格局及其时空变化特征

Spatio-Temporal Changes in America's Cropland over 2000-2010

【目的】耕地时空格局变化特征分析是地表覆盖研究的热点问题之一。美洲作为全球重要的粮食生产区,其耕地数量和分布具有全球性战略地位,科学分析美洲耕地时空格局变化特征、过程和规律为耕地可持续发展提供科学参考。【方法】基于GlobeLand30数据集,运用数理统计和GIS空间分析等方法,系统分析了2000—2010年美洲耕地面积数量变化、空间分布及类型转化特征,并重点分析了亚马逊地区耕地格局变化状况。【结果】2010年美洲耕地总面积为52 875.05×104 hm2;2000—2010年的10年间,美洲耕地总面积总体增加,面积增加约2 128.14×104 hm2,增幅约4.19%。耕地面积增加最大国家为巴西,幅度达到9.51%,位居美洲国家之首,其次为阿根廷;减少最大国家为厄瓜多尔,面积减少101.14×104 hm2。10年间美洲耕地复种指数增加2.42%,变化最为显著国家为巴拉圭、波多黎各。从耕地变化类型看,美洲新增耕地主要来源于林地、草地,而耕地减少主要是由于人造地表的侵占。美国耕地总量最多,但10年间耕地增长率较低,仅为0.08%,绝大部分损失的耕地转为人造地表,由于收获面积的减少导致复种指数减少了0.89%;巴西耕地总量仅次于美国,耕地大幅度增加主要来源于林地和草地,同时复种指数有较大程度提高。亚马逊地区作为美洲重要的生态和农业区域,10年间耕地增长8.41%,耕地增长伴随着森林、草地被大量破坏,尤其在巴西西南和厄瓜多尔表现最为剧烈。【结论】2000—2010年美洲耕地整体上呈现增加态势,国家间耕地利用格局变化差异明显;耕地主要来源于林地、草地和灌木,增长集中在巴西和阿根廷,耕地主要转出为人造地表,集中在美国。作为美洲重要的粮食生产区,亚马逊地区耕地面积和耕地复种指数都提高,两者同步增加一定程度上提高区域或全球粮食产量,但其带来的生态环境效益需要深入关注。

【Objective】The analysis of the spatial and temporal pattern of cropland is one of the hot issues of land surface research. As the world＇s most important grain production area, a spatio-temporal pattern analysis of America provides regional insight for cropland sustainable development with potential global applications.【Method】GlobeLand30—Cropland, mathematical statistics and GIS-based spatial analysis methods were adopted to explore the spatial-temporal characteristics of cropland area and conversion in America from 2000 to 2010, with particular emphasis on the Amazon region.【Result】This analysis shows that the total cropland area increased by 4.19% from 2000 to 2010 with 2 128.14×104 hm2, mainly converted from forest and grassland. The main conversion from cropland was to artificial surfaces. The major cropland expansion happened in Brazil with a rate of 9.51%, followed by Argentina. Ecuador showed the greatest decrease with 101.14×104 hm2. From 2000 to 2010, the multiple cropping index increased across the entire region by 2.42%, with Paraguay and Puerto Rico exhibiting the most significant changes. The United States of America had the most cropland area, however growth rate was only 0.08% and the multiple cropping index decreased by 0.89%. Brazil had the second highest amount of cropland area and a high rate of increase（9.51%）, with most of the new cropland converted from forest and grassland. As the most important agricultural district and ecoregion in America, the Amazon experienced a cropland increase of 8.41%, with the direct conversions mostly occurring in the southwest of Brazil and Ecuador.【Conclusion】The total amount of cropland in America increased during 2000-2010, but there were large differences between countries. The direct conversions to cropland were mainly from woodlands, grasslands and shrubland in Brazil and Argentina. Loss of cropland was primarily caused by conversion to artificial land. Additionally, the Amazon experienced a steady increase in both the area of cropland and the multiple cropping index. While these increases bolster the regional and global grain production, the ecological environmental effects require more consideration.