克里雅河中游土地利用/覆被与景观格局变化研究

干旱内陆河流在维系绿洲形成与发展,连接干旱区绿洲各类生态子系统中具有举足轻重的作用。以克里雅河中游为研究区,基于遥感影像分析了1995年、2005年和2015年3个时期的土地利用/覆被与景观格局变化特征,采用缓冲区分析法,揭示了土地利用/覆被与景观格局的时空变化特征,用土地覆被转移指数模型计算了土地利用转移方向。研究结果表明:1)1995—2015年,克里雅河中游耕地持续增加,草地和水体呈减少趋势,耕地增加和水体减少主要发生在河道附近,草地退化在绿洲边缘较严重。在河道附近,耕地主要由水体和草地转入,水体主要转出到耕地,而在绿洲边缘草地主要转出为其他用地;2)从景观水平看,研究区整体景观具有破碎化趋势,景观多样性降低,分离度变大,整个景观向均匀化发展,此变化在河道附近和绿洲边缘较明显。从类型水平看,耕地斑块数量持续增加,有向连片生成的趋势。草地斑块分离度越来越大,逐渐失去了在绿洲中的优势。水体有破碎化趋势;3)从土地转移指数看,研究区土地覆被总体变差;河道附近土地覆被经历了退化-改善的变化过程,而其他缓冲带则是持续退化,尤其绿洲边缘退化程度最为严重。

Land use and landscape pattern changes in the middle reaches of the Keriya River

Water is the main driving factor of oasis survival. Rivers play important role in maintaining the formation of ecological systems in arid regions. In this study, the spatial and temporal changes of land use/land cover and the landscape pattern in the middle reaches of the Keriya River were analyzed using the GIS technology through ArcGIS and Fragstats, based on remote sensing images from 1995, 2005, and 2015. A buffer analysis along the main river channel was conducted to analyze the spatial land use/land cover (LULC) characteristics and landscape patterns. A model was introduced to quantify the directions of LULC changes. The results were as follows:1) From 1995 to 2015, cropland area increased by 6.44%, while grassland and water area decreased by 16.69% and 4.38%, respectively. Cropland expansion and water area degradation primarily occurred along the river, and grassland degradation was mostly noted in the oasis-desert ecotone. Along the river, cropland area was mainly converted from the water area and grassland, and the water area was mostly converted into cropland. In the oasis-desert ecotone, grassland was mostly converted into unused land. 2) The landscape pattern also changed obviously. Landscape fragmentation increased, and diversity of the landscape decreased, which occurred along the river and oasis-desert ecotone most obviously. 3) Results of the LULC change direction model showed that a LULC change along the river experienced a process of degradation and slight melioration. In the other areas, the LULC change experienced continuous degradation.