|Alternative Title||Comparative study on land cover between the typical transects in Eastern and Southern fringes of Tibet Plateau by remote sensing technology|
|Place of Conferral||北京|
|Keyword||土地覆被 变化检测 遥感 尼泊尔 青藏高原|
近年来，气候变化和人类活动导致全球土地覆被剧烈变化，给人类的生活、生产及生存带来了重大影响。土地覆被变化研究成为全球变化研究的核心和热点研究领域之一。青藏高原的东缘和南缘区域，由于自然条件、人口、政策等差异，使得两个区域土地覆被空间分布格局和动态变化特征表现出明显差异。尼泊尔作为兴都库什-喜马拉雅区域的重要组成部分，是一个从平原到山地再到高原的典型过渡地带，境内土地覆被类型复杂多样。然而，目前有关尼泊尔的土地覆被研究多集中在流域、城镇尺度，研究目标也多服务于森林管理、土壤侵蚀等方面，而从国家尺度开展的土地覆被研究还较为缺乏。因此，在我国大力推行“一带一路”战略的前提下，本研究以中尼国际合作项目为科学支撑，以Landsat TM/ETM+多时相遥感影像为数据源，采用面向对象与决策树相结合的土地覆被遥感制图与变化检测方法，完成土地覆被遥感监测数据集构建。并且利用验证样本格网选取策略，结合Google Earth高分辨遥感影像获取土地覆被验证样本，并采用误差矩阵法完成土地覆被产品的精度验证。在此基础上，开展尼泊尔国家尺度土地覆被空间格局特征分析及其1990~2010年土地覆被动态变化特征分析，以及青藏高原东缘与南缘典型样带土地覆被特征对比分析。主要得到以下几点结论：（1）本研究生产了尼泊尔全境2010年土地覆被产品（文中简称NepalCover-2010）。经验证，产品一级类总体精度达94.83%，Kappa系数0.94，二级类总体精度达87.17%，Kappa系数0.85，是同类土地覆被产品中精度最高的。本产品能够反映尼泊尔土地覆被空间分布格局，并为后续分析提供数据保障。（2）林地是尼泊尔最主要的土地覆被类型，占国土面积比例约为41%。耕地次之，占国土面积比例约为25%，其中水田和旱地的比例约为2:3。地形和气象要素对尼泊尔土地覆被空间分布格局具有明显的影响。自南向北，随着海拔的不断增加，各土地覆被类型表现出水田、常绿阔叶林、旱地、常绿阔叶灌木林、常绿针叶林、草原、稀疏植被和冰川/永久积雪的垂直地带性特征。（3）1990~2010年，尼泊尔各土地覆被类型动态变化在不同发展区和不同时期均表现出明显的差异。东部和中部发展区土地覆被动态变化率更高，后十年(2000~2010)土地覆被动态变化率大于前十年(1990~2000)。各发展区之间自然环境和社会经济状况的差异，以及不同时期产业结构的比重和气候变化差异，是造成上述差异的主要因素。（4）近20年（1990~2010年）尼泊尔土地覆被类型发生变化区域的面积共有1,305.13 km2，约占尼泊尔国土面积的0.88%。其中，林地、灌木林、草地、湿地和冰川/永久积雪呈减少趋势，而耕地、人工表面和裸露地则呈增加趋势。气候变化，自然灾害，人口的持续增长和迁移，社会经济发展，以及森林保护等相关政策实施是尼泊尔土地覆被类型发生变化最主要的驱动因素。（5）青藏高原东缘与南缘典型样带各土地覆被类型随着海拔的不断增加，均表现出了明显的垂直地带性特征。近20年间（1990~2010年），两个样带土地覆被类型动态变化特征也具有明显的差异性。气候变化引发的自然表现（如湿地退化、河流改道）以及人类社会经济活动差异，是造成两个样带土地覆被动态变化特征差异的主要驱动因素。;
Climate change and human activities lead to global land cover change, which has brought enormous impacts on human life and production and survive, in recent years. The research on land cover change became a core and hot content of the global change research. Spatial distribution patterns and dynamic change characteristics of land cover classes have obvious differences in Eastern and Southern fringes of Tibet Plateau, due to the discrepancy of natural conditions, population and policies, etc. Nepal, located at the Southern fringe of Tibet Plateau, is representative of the land cover diversity in the Hindu-Kush-Himalayan region, due to its sophisticated and diverse land cover classes. Its topography shows typical transitions from Plain to Mountain, and then to Plateau. However, the current researches about land cover in Nepal mainly focus on the a lot of watershed or urban, and the research objectives mainly meet the requirements of the forest management and soil erosion, etc. Thus, the land cover research on national scale in Nepal is extremely rare. “The Belt and Road Initiative” has been vigorously promoted by Chinese goverment. Therefore, under the scientific support of the international cooperation project, the multi-temporal Landsat TM/ETM+ images were taken as main input data, and the combined method of object-oriented and decision trees were used to land cover mapping and change detection, and construct the land cover remote sensing monitor data sets. The strategy of validation sample selection in grids and high resolution images provided by Google Earth platform, and the error matrix method were used to verify the accuracy of the land cover product. This paper analyzes the patterns of spatial distribution on national scale, and analyzes the characteristics of land cover dynamic changes in Nepal from 1990 to 2010. Besides, comparisons of the features of land cover between the typical transect of Eastern fringe and Southern fringe of Tibet Plateau were performed. The main conclusions are summarized as follows.（1）This research produced a land cover product of 2010 for Nepal, hereinafter referred to as NepalCover-2010. The overall classification accuracies of primary and secondary classes for the NepalCover-2010 are 94.83% and 87.17%, respectively. The Kappa coefficients are 0.94 and 0.85, respectively. The NepalCover-2010 has the best accuracy compared with the similar land cover products. It’s able to reflect the spatial distribution pattern of land cover classes in Nepal, and provides exact data support for the subsequent analysis.（2）Forest is the major land cover class in Nepal, and accounts for 41% of the total land area of Nepal. Cultivated land is the secondary class in Nepal, which accounts for 25%. The area proportion of paddy field to that of dry land is about 2:3. Topographical and meteorological elements impact notably on spatial distribution of land cover classes in Nepal. Spatial distribution of each land cover class possesses characteristics of vertical zonality, and the appearance order of typical land cover classes is paddy fields, evergreen broadleaf forests, dry lands, evergreen broadleaf shrubs, evergreen needleleaf forests, steppes, sparse vegetation, snow and ice, from south to north, along with the increase of altitude. （3）The land cover dynamic changes in different development regions and different periods has shown significant differences from1990 to 2010 in Nepal. The land cover dynamic changes of Eastern Development Region and Central Development Region are more obvious, and the rate of land cover dynamic change in 1990s is higher than 2000s. The diversity of natural environment and socioeconomic status among the five development regions, and the discrepancies of climate change and proportion of industrial structure among different times, all of these were primary factors which resulted in above differences.（4）The area of land cover change has reached 1,305.13 km2 over past two decades(1990~2010) in Nepal, and accounted for 0.88% of the total land area. The area of forests, shrubs, grasslands, wetlands and permanent snow and ice had a decreasing trend. On the other hand, the area of cultivated lands, built-up lands and bare lands showed an increasing trend. The main drivers of the land cover changes in Nepal are climate change, natural disaster, population increase and migration, socioeconomic development, as well as implement relevant policy about forest protection, etc. （5）Spatial distribution of each land cover class has a distinctive features of vertical zonality in typical transects of Eastern and Southern fringes of Tibet Plateau, along with the increase of altitude. The characteristics of land cover dynamic change have marked disparity in two typical transects from 1990 to 2010. The major driving factors are different natural reflection induced by climate change, such as wetland degradation and river flow modification, as well as different human socioeconomic activities on the two typical transects.
|曹小敏. 青藏高原东缘与南缘典型样带土地覆被遥感监测对比研究[D]. 北京. 中国科学院大学,2016.|
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