【作者】 黎浩许；

【导师】 颉耀文；

【作者基本信息】 兰州大学 ， 地图学与地理信息系统， 2013， 硕士

【摘要】 额济纳绿洲位于我国第二大内陆河黑河的下游,为典型的内陆河尾闾绿洲,该区地处北温带干旱荒漠区,其气候属于极端干旱的大陆性气候。近几十年来,随着上中游绿洲的过度开发,下游绿洲植被退化、物种减少、绿洲萎缩、下垫面性质改变,生态环境日趋恶化。研究额济纳绿洲时空变化过程并分析其驱动机制,对绿洲的保护和利用具有重要意义。本文在RS和GIS技术支持下,利用高分辨率卫星相片(1963年,1968年,1980年)、Landsat MSS影像(1973年,1977年)、Landsat TM/ETM+影像(1986、1990、1993、1996、1999、2002、2006、2009年)多源长时间序列遥感数据,采用面向对象分割算法或自动阈值法进行了绿洲提取,同时对提取结果利用目视解译方法进行了调整,实现了对黑河下游绿洲边界的精确提取。对额济纳绿洲的时空变化过程、特征、规律进行了分析,从连续变化的角度对绿洲时空变化过程进行了阶段性划分,提出了固定不变型、“昙花一现”型、先非后是型、先是后非型,前稳后乱型、前乱后稳型、单峰型、波动型和反复无常型等9种绿洲时空变化模式,并对绿洲的稳定性进行了分析,论文的主要结论如下：1)、从数量变化和过程看,绿洲总面积总体上呈波动性扩大趋势。将绿洲面积的变化划分为“低位徘徊-急剧扩张-高位波动-陡然减少-稳定增加”五个阶段,分别以1977年,1986年,1996年和1999年为分界点。绿洲的纯增主要发生在1990年之前,但波动较大,1990年之后除个别几个时期扩张面积稍微大一点外,其它时期扩张面积都比较微小。绿洲的纯减比较有规律,从1968年的15053.0hm2持续减少到1986年的295.1hm2,之后减少面积比较微小。2)、从绿洲空间分布上看,绿洲主要分布东、西河的南部、西河沿岸以及额济纳盆地的三角洲地区,东河沿岸分布比较破碎。绿洲面积增加的区域主要分布在东河上游西部、西河上游东面、西河中游东面、黑河干流的西面、三角洲的西北、东北和东南面等。绿洲面积减少的区域主要分布在西河沿岸以及三角洲地区的东面和北面。3)、从绿洲变化模式看,绿洲变化可划分为固定不变型、“昙花一现”型、先非后是型、先是后非型,前稳后乱型、前乱后稳型、单峰型、波动型和反复无常型等9种模式,占总绿洲面积的比例分别为8.54%、23.61%、6.36%、0.62%、5.39%、15.27%、2.80%、16.97%和20.43%。其中“昙花一现”型所占比例最大,其次是反复无常型,说明近50年来,额济纳绿洲以不稳定状态占主导。4)、根据稳定性将绿洲划分为稳定型、不稳定型、很不稳定型,三者所占比例分别为33.48%、41.58%、24.94%。其中河流下游冲洪积三角洲平原、西河河流流经地区以及黑河干流西面的水库区绿洲表现得比较稳定,外围绿洲表现为不够稳定。5)、黑河下泄水量的变化是绿洲演变的根本原因,影响整个研究时段；人为活动的加剧与不科学的滥伐过牧是绿洲化的重要原因；气候暖干化等引发、加剧了自然灾害,对绿洲化也有一定的影响。各时期绿洲化的主要因子有所差异,计划经济时期的主要影响因子有政策、人口变化、上游来水量和自然灾害；市场经济时期的主要影响因子有政策、上游来水量、人为破坏、经济发展、土地盐碱化；生态建设时期主要影响因子有：上游来水量、经济利益、生态建设相关政策。更多还原

【Abstract】 Ejina Oasis, a typical tail oasis continental river, locates in downstream of Heihe River which is the second largest inland river in China. This region is in the desert area, with its climate belonging to extremely arid continental climate. In recent decades, for upper and middle reaches of Heihe River over exploitation, the ecological environment of the oasis is becoming worse and worse, such as vegetation degradation, species decline, oasis shrink, the underlying surface changes and so on. Studying spatial-temporal changes and analyzing driving mechanism has important significance in protecting and utilization oasis.Aim to accurate extraction the border of oasis, we choose object-oriented segmentation algorithm or automatic threshold method to extract oasis and adjust result adopting visual interpretation, utilizing long time series and multi-source remote sensing data (high-resolution satellite photo in1963,1968,1980, Landsat MSS images in1973,1977, landsat TM/ETM+images in1986,1990,1993,1996,1999,2002,2006,2009), in the support of RS and GIS. In the study, we have analyzed spatial-temporal changing process, characteristics, laws, and divided changing process into stages of the Ejina oasis, and gotten nine types of spatial-temporal variation patterns (permanent pattern, transient pattern, changeable pattern which from oasis to others, changeable pattern which from others to oasis, stable to chaos pattern, chaos to stable pattern, single peak pattern, wavy pattern, and capricious pattern), and analyze stability. Results of study are:Firstly, in view of area change and process, the total areas of oasis tend to expand fluctuately. The area changes was divided into five periods,"low fluctuation-rapid expansion-high volatility-sharp decrease-stable increase", by year of1977,1986,1996and1999as the cut-off points. The pure expansion of oasis mainly appear before1990with large fluctuations, and other periods expansion areas are small except several periods with slightly large expansion area after1990. The pure decrease is regular, which decreases from15053.0hm2in1968to295.1hm2in1986, afterwards the decreased area is very small.Secondly, in view of space distribution pattern, the oasis mainly distribute in south of East River and West River, West River coast, and the Delta region Ejina basin. It is broken distributed along the East River. Oasis area increased region are mainly distribute in the west of East River upstream and Heihe River, east of West River upstream and middle, and delta northwest, northeast and southeast. In the meanwhile, oasis area decreased regions locate in West River coast and delta east and north.Thirdly, in view of the oasis changing pattern, oasis variation can be divided into nine models, permanent pattern, transient pattern, changeable pattern which from oasis to others, changeable pattern which from others to oasis, stable to chaos pattern, chaos to stable pattern, single peak pattern, wavy pattern, and capricious pattern. Their proportion of the total area are8.54%,23.61%,6.36%,0.62%,5.39%,15.27%,2.80%,16.97%and20.43%, respectively. The transient pattern accounts for the largest share and the second is capricious pattern, which means Ejina oasis is unstable in recent50years.Fourthly, according to the stability, the oasis is divided into stable, unstable and highly unstable, and ratios are33.48%,41.58%and24.94%, respectively. The stable oasis is in alluvial delta plain of Heihe River downstream, West River flow region and the reservoir region of the west of Heihe River. Peripheral oasis is unstable.Fifth, discharged water change directly leads to the oasis development, affecting entire study phase. Intensified human activities, unscientific overgrazing and deforestation are the major reason for oasis development. Climate dryer and warmer cause and exacerbate natural disasters, and influence oasis development. The main factors differ in difference period. In planned economy period, factors are policy, population, upstream inflow and natural disasters. In market economy period, factors are policy, upstream inflow, human destruction, economic development and land salinization. Upstream inflow, economic benefits and relevant policy about ecological construction are factors in ecological construction period.更多还原