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 of ecosystem change and driving factors. In the impacts of the global change and the ecological construction in the 2000s,the land cover of China has changed significantly. Monitoring and analysis of this change not only can support China carbon source/sink evaluation and assessment of carbon budget, but also provide the basic data for the ecological environment evaluation. Supported by object-oriented classification technology, the land cover data of China ( ChinaCover) in 2000 and 2010 have been produced using Landsat TM/ETM and HJ-1 satellite data of 30m resolution, combined with a large number of data of field investigation. At the same time, vegetation coverage data has been produced using the dimidiate pixel model with resolution of 250m. This study has analyzed the change of China land cover changes based on the land cover data and vegetation coverage data of 2000 and 2010. Results have showed that: there have been a total of 19× 10~4km~2 land cover changes,accounting for about 2% of the China land area. The areas of woodland and artificial surface have been increased ; the areas of grassland, wetland and cultivated land have been decreased. The rapid increase of artificial surface and the mass reduction of cultivated land has been the main trend of land cover changes. The area of artificial surface has increased by 28. 7%,while the area of cultivated land has decreased by 4. 8x 10~4km~2, 2. 7% lower than in 2000. The conversion areas of cropland to artificial surface have been mainly concentrated in Eastern China; the conversion areas of cropland to forest and grassland have been mainly distributed in the areas where the “Regulations on Restoring Farmland to Forest" has been carried out; Arable land expansion has been mainly occurred in the Sanjiang plain and the Xinjiang oasis. The vegetation coverage changes of forest, shrub and grassland have showed an overall upward trend in 2000s. There have been 47. 3%,58. 8% and 55. 6% of the forest, shrub and grassland vegetation cover has been improved. But forest quality has had the trend of degradation in the Wenchuan earthquake-stricken area, Hengduan Mountains and Wuyi Mountain areas; shrub vegetation coverage has declined around the Tarim basin, eastern Tibet Plateau, Taihang Mountain, and Luliang Mountain areas ; grassland has been deteriorated in central Inner Mongolia,southwestern Tibet Plateau,southern Tianshan and Hulun Buir.