近40a凯拉库姆库区土地利用/覆盖变化及景观格局分析

为研究近40 a凯拉库姆库区土地利用/覆盖和景观格局时空变化状况,该文以凯拉库姆库区1975年Landsat MSS、1990年Landsat TM、2000年Landsat ETM+和2011年Landsat TM遥感影像为数据源,利用ENVI软件得到各时期的土地利用/覆盖类型转移矩阵,建立土地利用面积变化量、单一土地利用类型动态度以及区域土地利用综合动态度模型;同时,在景观格局分析中采用景观格局数量分析方法,在类型水平和景观水平分别选取不同的指数,系统分析凯拉库姆库区土地利用/覆盖和景观格局变化的时空特征。研究结果显示:近40 a凯拉库姆库区的土地利用/覆盖发生了剧烈变化,建设用地面积呈现出持续增加的态势,低覆盖度草地和未利用地的面积随时间序列呈"V"型变化,而水体、耕地、中覆盖度草地的面积随时间序列呈倒"V"型变化;建设用地和耕地大面积急剧扩张,并伴随着低覆盖度草地、中覆盖度草地和未利用地面积的减少,大量的中覆盖度草地、未利用地转化为耕地,同时部分耕地又转化为建设用地,使得建设用地和耕地面积显著增加,研究区区域土地利用综合动态度呈"V"字型变化,并有逐渐加快的趋势,活跃土地利用/覆盖类型由早期和中期的水体转化为近期低覆盖度草地,稳定土地利用/覆盖类型由早期的耕地和中覆盖度草地,过度到中期未利用地,进而转化为近期的耕地;景观格局分析表明,中覆盖度草地和耕地对整个景观发挥主导作用,与水体相邻的景观要素多,建设用地斑块数目多且相对分散,但有集中分布的趋势,在人类活动的影响下,整体斑块尺度趋于均匀,景观趋于丰富和复杂化,斑块聚集程度减少,破碎度增加。该研究结果为凯拉库姆库区水土地资源可持续开发和利用、生态环境保护提供科学依据。

Land use/cover dynamic change and landscape pattern analysis in Kayrakkum reservoir area during past 40 years

Abstract: For discussing the change of land use/cover and landscape patterns in Kayrakkum Reservoir during the past 40 years, remote sensing images, i.e., MSS in 1975, TM in 1990, ETM+ in 2000, and TM in 2011, were used as the data source. The transfer matrix of land use/cover type map superposition was obtained using ENVI software, to study the land use area change, the single type of land use dynamic degree, and the indices of land use dynamic degree model of regional land use. Furthermore, the spatial-temporal characteristics of land use and landscape pattern changes in the Kayrakkum Reservoir area were systematically analyzed by using the landscape pattern quantity analysis method and by selecting different indices in type and landscape levels. Results showed that tremendous changes had taken place in the past 40 years for the land use/cover in Kayrakkum Reservoir area. Construction land area showed a sustainable increase; while low coverage grassland and unutilized land area tended a 'V' shape over time. However, water, arable land and middle coverage grassland areas were all with inverted 'V' shapes. Overall, the construction land and arable land expanded largely, while the middle coverage grassland, low coverage grassland and unutilized land decreased. Also, a large number of middle coverage grassland and unused land were changed into cultivated land. At the same time, part of the cultivated land was changed into construction land, which resulted in a significant increase in construction land and farmland. The study area changed with a 'V' shape, with a gradually accelerating trend, The active land use/cover type changed from water at early and middle time to low coverage grassland recently, whereas the stable type of land use/cover changed from middle coverage grassland and arable land at an early time, to unutilized land at the middle time, and then recently to arable land. Landscape pattern analysis indicated that middle coverage grassland and arable land hold dominant positions in the whole landscape. More landscape elements were detected adjacent to aquatic land. Construction land showed more patch numbers and was relatively scattered in the trend of concentration distribution. The patch size tended to be uniform, landscape fragmentation and diversity of landscape types tended to increase, and the landscape aggregation degree tended to decrease under the influence of human activity. Moreover, low coverage grassland and arable land played a controlling role of the whole landscape. Because water is the source of an oasis's life, Kayrakkum reservoir has occupied an important position in the region's ecological system. With the changes in the economic system and the impact of human activities in nearly 40 years, the area of the reservoir and the water level had experienced tremendous changes, which had an important impact on the dynamic change of land cover and landscape pattern. The result could provide a scientific basis for ecological environment protection, as well as sustainable use of water and land resources.