【作者】 马利邦；

【导师】 牛叔文；

【作者基本信息】 兰州大学 ， 人文地理学， 2011， 博士

【摘要】 在气候变化和人类活动的双重影响下,我国西北干旱的绿洲区域生态环境进一步恶化,其中最突出的问题就是人类活动对水资源无序过度开发利用。人类活动导致环境变化的脆弱性显著增大,人口数量的增加、对有限资源的过度依赖及全球变暖等都意味着人类社会和生态环境比以往更加敏感和脆弱。甘肃省敦煌市气候极端干旱,生态十分脆弱。近些年来,由于人口数量的持续增长和耕地规模不断扩大,水资源消耗过度,环境明显退化,著名的人类文化遗产莫高窟及自然奇观鸣沙山、月牙泉等的存衍受到严重威胁,引起国内外的广泛关注。因此,本文将该区域作为研究对象,以1987、1990、1996、2000和2007年五期的Landsat—5TM遥感影像、1954—2008年的气候观测资料和1987—2007社会经济统计数据等为数据源,综合应用实地调查、“3s”技术、生态空间分析、模型模拟等方法,从不同角度和层次分析敦煌市近20年来的生态环境演变过程及驱动机制,并提出了生态环境保护与恢复的途径及可持续发展实验区建设的模式,为该区域水土资源的合理利用和生态保护提供依据。得到了以下基本结果和认识：第一,敦煌市土地利用/覆盖变化的总体特征分析。敦煌绿洲主要分布在海拔1200m以下(占总面积的98.4%)、坡度小于1°的区域(占总面积的61.01%),且呈现明显的依水分布态势。在过去的20年间,敦煌市荒漠包围绿洲的独特的景观格局基本没有改变。在8类土地利用/覆盖类型中无植被区所占比例最大,达85%以上。第二,敦煌市土地利用/覆盖变化的时空特征分析。在时间上,总体表现为植被覆盖空间范围收缩,生态明显退化。空间上,耕作区边缘植被覆盖程度有所增加,耕地向外扩张；水域湿地、高、中、低覆盖度草地和灌木林地均为从斑块的边缘区域逐渐向中心区域萎缩,无植被区则呈现出完全相反的变化趋势,主要是从斑块边缘向外逐渐扩张。第三,敦煌市土地利用/覆盖类型的演变方式、方向、规模和速度分析。敦煌市土地利用/覆盖演变方式各异,呈现出单向演变为主,渐次演变和逆向演变相对较少的特点。土地利用/覆盖演变的方向和规模存在较大差异,耕作区的增加主要是由部分草地和无植被区转变而来,水域湿地和林地则向草地转变,总面积变小,高覆盖度草地转变为中覆盖度草地、中覆盖度草地转变为低覆盖度草地、而低覆盖度草地转变为无植被区、城建用地主要由耕作区和无植被区转变而来。2个时段的综合土地利用动态度分别为0.56%和0.66%,反映出后期LUCC的强度相对于前期更加剧烈。第四,敦煌市土地利用格局演变的情景模拟。基于Markov过程模型和CLUE-S模型对敦煌市土地利用格局进行模拟和预测,模拟结果精度较高。通过修正土地利用/覆盖类型之间的转移概率矩阵,设置自然发展型、生态保护型、经济发展型和综合发展型四种情景模式,可以看出在不同的情景模式下,研究区域土地利用/覆盖空间格局差异较大。综合发展型情景比较全面的考虑了生态环境恢复、经济发展等的需要,模拟结果较好,是一种比较理想的发展方式。第五,敦煌市生态环境要素变化分析。依据实际测定的样方生物量与对应的土地利用/覆盖类型的面积拟合曲线,估算地表生物量。表明近20年来地表生物量共减少170856.52t,年均减少5.8%0,其中天然绿洲生物量净减,人工绿洲生物量净增,总生物量减少与天然绿洲生物量减少有很强的对应关系。基于生物量的大小和实际功用估算的生态系统服务总价值,20年间共减少43127.44×104元,年均减少2156.37×104元。随着直接使用价值增加,间接使用价值减少较快。这意味着人工生态系统价值的较快增长是以自然生态系统价值的减少为代价的,表明人类活动已显著影响到区域的可持续发展。第六,敦煌市生态环境演变的驱动机制分析。在本文研究时间尺度内,引起敦煌市生态环境演变的因素主要来自自然和人文两个方面。在全球气候变化的大背景下,温度升高对植被生长具有一定的影响,而土地开垦、灌溉、旅游等人类活动加大了对水资源的需求,挤占生态用水,这是植被退化、自然生态系统萎缩的主要原因。从主成分分析和逐步回归分析的结果看出,人文因素是生态环境演变的主要驱动因素,尤其是人口增长、农业生产、技术进步和生活水平,最终的结果都可归结为对水资源的影响。第七,人类活动对敦煌市生态环境演变的影响。两种土地利用/覆盖类型相互替代的比量关系中,耕作区替代关系明显,每增加1km2最少替代1.33km2的灌木林地,最大可替代42.57km2的低覆盖度草地。敦煌市自然植被和人类活动的用水量此消彼长,总用水规模在6.3×108m3左右。自然植被用水量从1987年的3.0727×108m3减少到2007年的2.17×108m3,净减少达30%,20年累计减少量达9.5017×108m3。人类活动用水量从1987年的3.3157×108m3增加到2007年的4.093×108m3,20年累计增加量达5.9155×108m3。根据水土平衡原理估算出,常规地面灌溉条件下,研究区域适宜绿洲面积为653.45km2,在节水灌溉条件下,适宜绿洲面积为909.65km2,均远小于目前的实际面积。第八,基于目前敦煌市生态环境面临的严峻态势,为了实现区域社会、生态、经济的协调持续发展,需要从水资源可持续利用、生态修复和重建、产业结构调整、制度保证及生态规划制定等多方面入手保护和恢复生态环境,并建立适度人口发展、循环经济发展、资源节约高效、生态环境保护和文化遗产保护的相互依存、相互制约的可持续发展模式,实现实验区又快、又好的发展。更多还原

【Abstract】 Under the dual influences of climate change and human activities, the ecological environment of arid oasis in Northwest China is in further deterioration, and the most prominent problem is water resources used over-exploitation by human activities. The vulnerability of environment change induced by human activities increases significantly, the increase in population, over dependence on limited resources and global wanning are all mean that human society and ecological environment will be more sensitive and vulnerable than ever. The climate is extremely arid and ecology is very fragile of Dunhuang City in Gansu province. In recent years, with the continued population growth and arable land expansion, water over-consumption and significant environmental degradation have become serious threats to the existence of the famous human cultural heritage Mogao Grottoes, the nature scenic Mingsha Hill and Crescent Moon Spring, which aroused wide attention at home and abroad. So. this paper took Dunhuang City as a study area, and used Landsat-5 TM remote sensing images in 1987,1990,1996.2000 and 2007, climate observations data from 1954 to 2008, socio-economic statistical data from 1987 to 2007 as the data sources, and by comprehensive application of field survey, "3S" technology, ecological spatial analysis, model simulation and other methods, the ecological environment change process and driving mechanism are analyzed in the last 20 years from different angles and levels, and the way to environmental protection and restoration, the model for test zone of sustainable development are proposed, which can provide basis for the rational use of water-land resources and ecological protection. The basic results and understandings from the thesis are as follows:Firstly, analysis on the general characteristics of land use/cover change in Dunhuang City. Dunhuang oasis is mainly distributed along the river, and in the area where the elevation under 1200m (98.4% of total area), slope less than 1°(61.01% of total area). Over the past 20 years, the unique landscape pattern, oasis surrounded by desert, has not changed in Dunhuang City. For the eight types of land use/cover, non-vegetation area take the largest proportion(above 85%). Secondly, analysis on the temporal and spatial characteristics of land use/cover change in Dunhuang City. From temporal aspect. the spatial extent of vegetation-coverage was shrinking continuously, ecological environment degraded significantly. From spatial aspect, vegetation coverage in the edge region of crop land increased, crop land area expanded outwardly; water-wet land, shrub land, high coverage grassland, moderate coverage grassland and low coverage grassland in other regions shrinked from edge to central, and no-vegetation area showed an opposite trend, which is expanded mainly from edge to outward..Thirdly, analysis on the changing ways, direction, scale and speed of land use/cover types in Dunhuang City. The changing ways of land use/cover are different, which showed a feature that the unidirectional change is the main way, gradually change and retrograde change are fewer relatively. Also, there are big differences in changing scale and speed of land use/cover, part of grassland and non-vegetation area transformed into the cultivation areas, part of water-wet land and shrub land changed into the grassland, and the grassland from high coverage to medium one, low one and non-vegetation land in successive steps. The comprehensive dynamic degree of land use from 1987 to 1996 and 1996 to 2007 are 0.56% and 0.66% respectively, which showed that land use/cover change of the latter phases is more significant than the previous phase.Fourthly, scenario simulation of land-use pattern in Dunhuang City. Based on Markov process model and CLUE-S model, the simulation and prediction are conducted on the land use pattern of Dunhuang City, the results show high accuracy. By modifying the transition probability matrix among different land use/cover types, we set four scenarios types:natural development type, ecological protection type, economic development type and comprehensive development type. It can be seen that from different scenarios, the spatial pattern of land use/cover in study area shows a great difference. Comprehensive development scenario is an ideal development way, because it can make up the above shortcomings, and make more comprehensive consideration in the needs of ecological environment restoration and economic development. In addition, the simulation results are good.Fifthly, analysis on the change of ecological environment factors in Dunhuang City. According to actual quadrat biomass measured and its corresponding fitting curves of land use area, total ground biomass was estimated. The results demonstrate that the total ground biomass decreased by 170856.52t, with an annual average reduction of 5.8%o. Among these, biomass of natural oasis shows a net decrease, while the biomass of artificial oasis shows a net increase,. There is a strong correspondence relationship between the decreasing of total biomass and the decreasing of natural oasis biomass. Based on the size of the biomass and the actual function, the total service value of ecosystem was estimated. The value decreases 43127.44×104 yuan from 1987 to 2007, and average annual decreases 2156.37×104 yuan. With the direct use value increased, the indirect use value reduces quickly. It means that the rapid growth of the value of artificial ecosystems resulted from high loss of the value of natural ecosystems, and showes that human activity has a significant impact on regional sustainable development.Sixthly, analysis on the driving mechanism of ecological environment change in Dunhuang City. During the time scale in this study, the factors that caused ecological environment change in Dunhuang City are mainly come from natural and human aspects. On the background of global climate change, although increased temperature has a certain effect on vegetation growth, land reclamation, irrigation, tourism and other human activities increase the demand for water resources, and diverted ecological water, which are the main reasons for vegetation and natural eco-system degradation. The principal component and stepwise regression analysis show that human factors are the mainly driving factors which caused ecological environment change, especially from the final test results of population growth, agricultural production, technological progress and living standard, they can be come down to the impact on water resources.Seventhly, the influence of human activities on the environment change in Dunhuang City. From the quantity ratio relationship between two land use/cover types which substitute for each other, we can see that crop land has a clearly substitute relationship, increasing of 1.33km2 shrub land at least can substitute 42.57 km2 low coverage grassland at most.Water consumption of natural vegetation decreases with the increased water consumption of human activities, and the total water consumption scale is about 6.3×108m3.Water consumption of natural vegetation decreases from 3.0727×10 m3 to 2.17×108m3 during this period (nearly 30%), cumulative reduction is 9.5017×108m3 for the past 20 years. Water consumption of human activities increases from 3.3157×108m3 to 4.093×108m3 during this period, cumulative addition is 5.9155×108m3 for the past 20 years.From the estimation based on soil-water balance principle, it can be seen that in the conventional surface irrigation conditions, the suitable oasis in study area is 653.45km2,and in water-saving irrigation conditions, the suitable oasis is 909.65km2, which is much smaller than the current actual area.Eighthly, Based on the current severe situation of ecological environment in Dunhuang City. in order to achieve the coordinated and sustainable development among society, ecology and economy, ecological environment need to be protected and restored from the following aspects, sustainable utilization of water resources, ecological restoration and reconstruction, industrial restructuring. system assurance, ecological planning and so on. Meanwhile, sustainable development model of mutual dependence and mutual restriction should be established, including appropriate population growth, circular economy, resource conservation and efficient, eco-environmental protection and cultural heritage protection, which can achieve the faster and better development of experimental zone.更多还原