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土地覆盖变化是陆地生态系统变化的重要组成部分与驱动因素。在全球变化、生态环境建设、经济高速发展等因素的影响下,21世纪前十年中国土地覆盖发生了显著变化,对此变化的监测和分析不但能支持中国碳源/汇的评估和碳收支估算,还可为生态环境变化评估提供基础数据。本研究在面向对象(object-based)的分类技术支持下,利用Landsat TM/ETM数据和HJ-1卫星数据,结合大量外业调查数据生产了30m分辨率的2000年、2010年中国土地覆盖数据(ChinaCover);采用像元二分法生产了植被覆盖度数据。利用这两个数据集对中国土地覆盖10年的变化特点进行了分析。结果表明,人工表面和林地呈增加趋势,而耕地、湿地和草地面积呈减少的趋势;人工表面的快速增加和耕地面积的大规模减少是这一时期中国土地覆盖变化的最主要特点;土地覆盖类型转换中,耕地转换为人工表面的区域主要集中在我国中东部地区,耕地转换为林地和草地的区域主要分布在退耕还林还草的重点区域,耕地的扩张主要来自三江平原和新疆绿洲的农业开发。以植被覆盖度为评估指标显示森林、灌丛和草地质量总体呈上升趋势,但在汶川地震重灾区、横断山以及武夷山等局部地区的森林质量呈退化趋势;塔里木盆地周围、青藏高原东部、太行山、吕梁山等地区的灌丛植被覆盖度有所下降;内蒙古中部、青藏高原西南部、新疆天山南部、呼伦贝尔等地区的草地出现退化现象。
Land cover change is an important part and driver of terrestrial ecosystem change. Under the influence of global changes, ecological environment construction and rapid economic development, land cover in China has undergone significant changes in the first decade of the 21st century. Monitoring and analyzing this change will not only support China’s carbon source / sink assessment and carbon sequestration Branch estimates, but also for the assessment of changes in ecological environment to provide basic data. Based on the object-based classification technology, Landsat TM / ETM data and HJ-1 satellite data are used in this study to produce 30m-resolution 2000 and 2010 land cover data (ChinaCover); Vegetation coverage data was generated using pixel dichotomy. The two datasets are used to analyze the ten-year land cover changes in China. The results showed that the artificial surface and woodland tended to increase while the area of cultivated land, wetland and grassland tended to decrease. The rapid increase of artificial surface and the large-scale reduction of cultivated land area were the main characteristics of land cover change in China during this period. In the type conversion, the area of cultivated land converted to artificial surface is mainly concentrated in the central and eastern regions of China. The area converted from cultivated land to forest land and grassland is mainly distributed in key areas of returning farmland to forest and grassland. The expansion of cultivated land mainly comes from the Sanjiang Plain and Xinjiang oasis Agricultural development. Vegetation coverage as an assessment index showed that the quality of forest, shrub and grassland generally showed an upward trend, but the forest quality in some areas hardest hit by the Wenchuan earthquake, Hengduan Mountain and Wuyi Mountain tended to degenerate. Around the Tarim Basin, the eastern part of the Qinghai-Tibet Plateau, , Lvliangshan and other areas of shrub vegetation coverage decreased; Inner Mongolia, southwestern Tibetan Plateau, southern Xinjiang Tianshan, Hulun Buir and other areas of grassland degradation.