瓜州县作为丝绸之路的边塞重镇,瓜州绿洲在保持东西段的经济联系中具有重要作用.以遥感影像为数据源,分别提取1986年、1990年、1995年、2000年、2005年、2010年和2015年间的绿洲分布信息,并使用格网化的方法,分析瓜州绿洲变化的时空过程和空间规律.结果表明:过去30年间,瓜州绿洲总体为增长的趋势,面积净增长278.874km2,相比于1986年,绿洲扩张49.6％,其中2000年以前绿洲的扩张速度较慢,2000-2005年为绿洲扩张的巅峰时期,其次为2005-2015年.空间分布上,昌马灌区绿洲不断向冲积平原前缘和向西扩张,主要为移民区域的耕地开发;疏勒河干流灌区的绿洲扩张是以原始绿洲为基础,呈散射状向外发展;疏勒河尾闾的绿洲规模较小、斑块分散,但在近几十年间也得到了较大程度的扩张.对于绿洲退缩而言,主要发生在昌马冲积平原区,面积较少,主要是由于该区域分布的较多天然植被,在受环境因素的影响下变化频繁.总结绿洲的变化过程可以看出,瓜州绿洲的扩张速度较快,扩张特征明显.昌马冲积扇前平原作为一个较典型的扩张区域,绿洲不断向北部细土平原扩张,但由于该区域本身的地下水位较浅,地表盐渍化现象严重,加之大量地表水利工程的建立,盐渍化的防护和治理成为了确保该区域绿洲长期稳定发展需要考虑的重要问题之一.%The oases of Guazhou County (China) play an important role in connecting the western and eastern economies and in developing the Hexi section of the Silk Road.In the present study,remote sensing images (L.aandsat5TM from 1986,1990,1995,2000,2005,and 2010 and Landsat8 from 2015) were used to elucidate the distribution of oases in Guazhou.The study area was divided into grids of 90 × 90 m,and the relative area change (KsridT1-T2) and accumulative area change rate (CKgird) were calculated as the expansion,retreat,or no change in every grid of each study period compared to the grid area and the sum of absolute Kgrid values to reflect the level of change (i.e.,weak,strong,acute,none),respectively,over the last 30 years.The qualitative description and classification of these two indicators were used to analyze the spatiotemporal and spatial regularity of changes in Guazhou oases.Our analyses revealed that (1) oasis area expanded consistently and significantly over the last 30 years,by 278.874 km2(49.6％);(2) oasis expansion mainly occurred after 2000,especially between 2000 and 2005 (38.45％),followed by the period between 2005 and 2015 (19.58％),but was lower before 2000 (12.6％);(3) oases were distributed in three areas,with Changma alluvial plain oases mainly expanding in immigrant towns,mainly to the front and west,the Shule River irrigation oases were scattered outwards based on the origin oasis of every period,and the small and dispersed river tail oases exhibiting relatively large expansion;(4) oases retreat occurred in the Changma alluvial plain,which possessed more natural vegetation,which is easily influenced by environment factors;and (5) oasis expansion has increased over the last 30 years.The Changma irrigation oases,as a typical expansion area,gradually expanded to the northern fine plain;however,due to the shallow water table in the region itself,surface salinization is serious,coupled with a large number of surface water projects generated in oasis development,salinization prevention and control has become an important issue in the region to ensure long-term stable development of oasis to considered.
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