基于移动窗口法的肃州绿洲化与景观破碎化时空变化

以甘肃省酒泉市肃州绿洲为例,以1990、1999和2010年3期Landsat TM/ETM同月相数据为数据源,基于Arc GIS与Fragstats软件,采用移动窗口法、转移矩阵和景观指数等开展绿洲化与景观破碎化的时空变化研究。结果表明:(1)肃州绿洲化过程主要表现为绿洲面积变化和内部土地利用类型之间的转化。绿洲面积变化以耕地、草地和城市建设用地等的增加为主;绿洲土地利用类型转换主要表现为耕地内部变化、草地与未利用地,城市建设用地与未利用地之间的转换等。(2)景观破碎化程度整体上呈减缓趋势,其剧变区多集中于绿洲边缘的银达镇、三墩镇、黄泥堡乡和下河清乡等,景观破碎化在空间上表现为由绿洲内部向边缘区转移。(3)以草地为主的绿洲荒漠过渡带是绿洲扩张和景观破碎化的多发区,更是维持绿洲稳定和可持续发展的关键子区。研究可为绿洲景观管理和可持续发展提供科学依据。

Spatiotemporal change and landscape fragmentation in suzhou oasis using the moving window method

Study of land-use and land-cover change is at the forefront of global environmental change research. Oases are unique geographical desert features that allow flourishing vegetation and human settlements, and sensitive to environmental change in arid areas. Research focusing on landscape index analysis of oasis development and the spatial relationships of landscape fragmentation is relatively rare and recent. The combined use of land cover classification based on remote sensing data and landscape metrics has provided a useful comprehensive understanding of the features of landscape structure and the ecological processes underlying these. In this study, we analyzed landscape fragmentation and change in Suzhou oasis, a typical agricultural oasis in the middle reach of the Heihe River watershed. To study oasis change and landscape fragmentation, oasis maps were obtained from Landsat TM/ETM images 1990, 1999 and 2010. The "Dynamic degree" and "Relative rate of change" were used to describe oasis change. We analyzed the relationships between oasis change and landscape fragmentation for 15 sample towns using correlograms and the moving window method. From 1990 to 2010, changes in oasis land-use were primarily an increase in farmland, grassland and human construction. Oasis area increased mainly due to the conversion of farmland, unused land to grassland, and rapid urbanization. Landscape fragmentation indices changed over time in the 15 towns, there were decreases in number of patches (NP), patch density (PD) and largest patch index (LPI), and increases in division index (DIV) and Shannon''s density index (SHDI), suggesting that the rate of landscape fragmentation slowed down gradually. The most dramatically changed areas were at the margin of Suzhou Oasis, such as Yinda Township, Sandun Township, Huangnibao Township, and Xiaheqing Township. Landscape fragmentation increased with the rapid change in oasis area and inner structural change in the edge zone. The ecotone, dominated by grassland, between the oasis and desert, was the main area where the oasis expanded and fragmented, and also the subarea key to maintaining oasis stability and managing sustainable development. In conclusion, it is vital to understand the relationships between oasification, human land-use change, and landscape fragmentation. This research is useful for landscape management and sustainable development of oases in arid areas of China.