青藏高原土地利用与覆被变化的时空特征

Spatial and temporal characteristics of land use and cover changes in the Tibetan Plateau

青藏高原土地利用与土地覆被变化(LUCC)研究是区域土地科学与全球变化科学研究的重要内容,也是保障高原生态安全屏障功能稳定与提升的科学基础.本文通过对已有LUCC数据与成果的再分析,研究了高原整体LUCC时空特征、典型区LUCC的时空过程及典型类型的变化过程与机制.结果表明:青藏高原土地利用与土地覆被结构稳定,一级地类变化面积比例低于7%,并以单次变化为主,土地覆被状况总体改善.近年来高寒草地覆被状况整体好转、局部退化,林地恢复良好,耕地基本稳定,建设用地显著扩张,裸地轻微减少.人口较为密集的河湟谷地与'一江两河'地区,建设用地、耕地、人工林地等增加明显;藏北高原和三江源等牧区,超载过牧和生态建设的作用均有体现;珠穆朗玛峰国家级自然保护地区土地覆被类型多样、变化复杂,并表现出对气候变化和人类活动有较强的敏感性.高原土地变化研究中还存在现有数据产品数量不足、精度不高,土地利用变化过程及其环境效应认识不够深入等问题,需要加强野外监测和遥感技术的结合,关注LULC在不同时空尺度下的变化特征,同时注重土地利用与土地覆被类型转化和类内渐变,使高原LUCC研究更好地服务于高原生态安全屏障建设和区域可持续发展.

The Tibetan Plateau(TP)is an important ecological security barrier for China and,indeed,for all Asia.Land use and land cover changes in the plateau not only affect the ecological environment and regional development of the plateau itself but also affect the stability and economic development of ecosystems in eastern China and other parts of Asia.This paper is based on an examination of the achievements of land use and cover change in the TP and a reanalysis of data including that of Climate Change Initiative Land Cover from 1992 to 2015;land use data provided by the Resource and Environmental Science Data Center of the Chinese Academy of Sciences for 1995,2000,2010 and 2015;and statistical data from Qinghai and Tibet.The paper analyzes the overall characteristics of land use and land cover changes in the TP and the spatial and temporal processes and their driving forces of land use and land cover change in typical regions and land types.This research is important not only for land change science and global change research but also for the promotion of the plateau and its adjacent areas.In recent decades,research has shown that the land use and land cover structure of the TP is stable,and the proportion of first-level land use type change was less than 7%from 1992 to 2015.Most of these changes are single time changes,with multiple land change occurring only in 1.85%of the total change area.The quality of land cover has been improved in areas where no land type change occurred.The Normalized Difference Vegetation Index(NDVI)showed an increasing trend in 24.45%of the area and a decreasing trend in only 1.31%of the area.The area of cultivated land,forest,grassland,wetland,and construction land on the plateau has increased,whereas bare land,glacier,and snow cover area has decreased.In most parts of the TP,the quality of alpine grassland has improved;however,in some areas,it has degraded at a local scale.Most of the woodland has recovered well after phased changes.Prior to 1980,there was a rapid increase in cultivated land area,but this has since become stable with only minor increases.However,the utilization intensity of cultivated land has increased significantly in recent years.Construction land has expanded significantly,and the recent growth rate has accelerated since 2010.Both the increasing speed of change and the construction land area in Qinghai Province are higher than in Tibet.There has been a general trend of a slight decrease in bare land change.In densely populated areas in the Yellow River-Huangshui River Valley and the One-River-Two-Tributaries area,land types that are closely related to human utilization such as construction land,cultivated land,and artificial woodland have undergone obvious changes.In pastoral areas,such as the Northern Tibetan Plateau and the Source Regions of The Three Rivers,overgrazing and ecological construction have significantly affected land cover.In the Qomolangma National Nature Preserve,land use types are diverse;changes are complex;and land cover is more sensitive to both climate change and human activity.There are limitations to the study of land change in the plateau,such as the difficulty of meeting the needs of ecological construction with existing data and the lack of in-depth understanding of the process of land use change and its environmental effects.Field monitoring and remote sensing techniques must be strengthened in order to clarify the process of land use intensity change and its impact on the ecological environment of the TP.These improvements will better serve the construction of an ecological security barrier and the sustainable development of the region.