【作者】 成军锋；

【导师】 赵秀海；

【作者基本信息】 北京林业大学 ， 生态学， 2010， 博士

【摘要】 土地荒漠化是是全球最突出的生态环境问题之一,直接影响了36亿ha的土地,占干旱区土地面积的70%,它作为极其严重的环境和社会经济问题困扰着世界,威胁着人类的生存和发展。我国沙漠化土地主要分布在北方干旱、半干旱和部分半湿润地区,从东北到西北形成一条不连续的弧形分布带。乌兰布和沙漠及周边地区位于我国北方农牧交错带的西部,是我国北方土地荒漠化较严重的地区之一,其自然环境具有典型的过渡性和脆弱性。草原文化与农耕文化的长期融合形成了草地与沙地交错的自然景观和农牧交错、蒙汉杂居的人文景观,因而成为土地利用变化研究的典型区域。本研究选用1985年、1995年、2000年、2004年4个夏季植物长势较好时期的Landsat TM影像影像图,同时收集1984-2005年的自然、社会经济数据,利用ERDAS IMAGE、ArcView GIS、Arcview、SPSS等软件,对研究区的土地利用／土地覆盖格局、动态、变化机制进行分析,结果如下：(1)依据干燥指数、地貌、土壤、植被、水文地质、风沙运动等自然因素和人类活动及行政区划将研究区分为4个亚区,分别是河套平原区、鄂尔多斯高原区、银川平原区和阿拉善高原区,分别代表不同的生态环境类型。(2)在整个研究区内,草地和未利用土地共同组成基质,两者占总面积的85%以上。通过景观格局指数的变化分析发现,1985-2004年,斑块整合,形状变得复杂,各斑块面积差异减小。对于不同的亚区,土地利用格局有所差异：绿洲景观,如河套平原区和银川平原区,由于自然条件和人为因素的限制,耕地、草地是基质,景观破碎度大,平均斑块面积小,差异也小,形状规则；而作为荒漠化的地区,受气候的影响,鄂尔多斯高原区的基质是草地,阿拉善高原区的基质是未利用土地,两个地区的景观异质性程度下降,斑块形状趋于简单,景观愈来愈由少数斑块类型控制,其中未利用土地不但总面积在增加,而且斑块越来越大,这对沙漠化治理越来越不利。(3)在整个研究区,耕地、林地、城乡工矿居民用地和未利用土地增加,草地、水域减少,在三个时间段,各种土地利用类型变化的趋势不同。从单一土地利用动态度和综合土地利用动态度来看,整个研究区的变化率远远小于分区的变化率,说明在整个研究区,土地利用变化很小,而在局部地区变化很大,这一方面反映了,未利用土地,尤其是荒漠化的日益严重与自然因素的恶化有关,另一方面也反映了在短期内,局部的人类活动对土地利用频繁而强烈的影响。从转化方向上看,耕地、林地、工矿用地和未利用土地向草地的转化反映了荒漠化地区的退耕还林还草工作的开展取得了初步成效,但同时草地向未利用土地的大量转化,也反映出了该地区局部荒漠化的加剧,荒漠化防治工作任重而道远。在绿洲地区,盐碱地增加,土地盐碱化程度加重,并且来源于滩地、戈壁和耕地的转化,这是绿洲建设中一个不容忽视的问题。(4)通过对阿拉善地区荒漠化的主因子分析,可以看出,影响当地荒漠化的因素主要是自然因素与人为因素的综合作用。自然因素包括气候、土壤等。人为因素包括人口过度增长、过度垦荒、过度放牧、水资源的不合理利用、决策失误等。干旱荒漠地区由于恶劣的自然条件,荒漠化自我逆转的可能性很小,必须采取有力的措施才能得以治理。(5)以鄂尔多斯南部为例,对近期荒漠化动态进行研究发现,从1991-2004年,无荒漠化面积基本保持不变,重度荒漠化面积大幅减少,斑块复杂性降低,轻度和中度荒漠化增加,同时不同荒漠化程度的斑块转化频繁,研究区的荒漠化程度在减弱,荒漠化程度处于中度荒漠化。影响研究区植被覆盖度变化的主要原因有：一是自然因素,研究表明降雨量的增加有利于植被的恢复,且存在滞后效应。二是人为因素,荒漠化防治措施的实施对该地区生态环境的改善起到积极的影响。在半干旱地区,水分、植被较干旱地区稍好,如果消除人为干扰,有自我逆转的可能,但具有反复性。更多还原

【Abstract】 Desertification is one of the world’s most prominent problem of ecological environment, which directly affect 3.6 billion ha of land, and account for 70% of land area, to threat human survival and development. Desertification land in China are mainly distributed in the northern arid, semi-arid and partial sub-humid, to form a discontinuous arc-shaped distribution belt from Northeast to Northwest. Ulanbh Desert and its surrounding areas locate China’s western region of farming-pastoral ecotone which has a typical fragility and transition of natural environment. As a result of climate change, the long-term integration of grassland culture and farming culture has formed nature landscape, which farm and sand stagger, and human landscape, which is chartistic of farmin-pastoral and mixed residence of Mongolians and Han Nationality so as to become typical region for study LUCC of fragile farming-pastoral ecotone.In this study,4 Landsat TM images of summer of 1985,1995,2000,2004, were chosen, which had better plant growth, and collected natural, socio-economic data, to study land use/land cover pattern, dynamics, change mechanism, with ERDAS IMAGE、Arc View GIS、Arcview、SPSS. The results are as follows:(1) Based on aridity index, geomorphology, soil, vegetation, hydrogeology and sand movement, human activity, and administrative division, the study area was divided into 4 sub-regions, that is, Hetao plain sub-region, Ordos pleatu sub-region, Yinchuan plain sub-region, Alashan plateau sub-region to represent different ecological environment types.(2) In the entire study area, grassland and unused land form matrix jointly, which accounted for 41.50～53.68%,36.11～48.07% respectively. From 1985 to 2004, number, edge density, mean patch edge, mean shape index, area weighted mean shape index decreased, while mean patch size, mean patch fractal dimension, area weighted mean patch fractal dimension, shannon diversity index and shannon evenness index increased to show patch integration, complexity of shape, balance of land use types, reducation of area difference. Relatively stable land use/land cover results from nature factor and human factor. Different sub-regions have drfferent land use pattern. Oasis landscape, such as, Hetao plain sub-region, Yinchuan plain sub-region, farmland and grassland are matrix, due to natural conditions and human factors. As desertification region, the matrix of Ordos pleatu sub-region and Alashan plateau sub-region is grassland and unused land, which landscape is increasingly controlled by a handful of patches. Not only total area of unused land increased but also patch area increased so as to be more and more unfavorable to desertification control.(3) In entire study area, farmland, forest land, resident land and unused land increased while grassland and water body reduced. In 3 time periods, the trend of LUCC is different. Farmland, water body and unused land reduced, and increased, and reduced. Forest land reduced continuously after increase. Grassland and resident land increased, and reduced, and increased. like results of sub-region, single land use dynamic degree in 1995-2000 was larger than that of the other two time periods, but change rate of entire area was far less than that of sub-regions, which show that, in general, land use change of entire area was small, and local change was large. On the one hand, it reflects that worsening desertification is related to deterioration of natural condition, on the other hand, in the short term, local human activities impact on land use frequently and strongly. Comprehensive land use dynamic degree in 1995-2000 was the biggest while that in 2000-2004 was the smallest, in line with single land use dynamic degree. As to land use transfer matrix, we can not simply consider transition probability, in the mean time, we must also consider transfer area, because small probability change of large matrix may lead to huge area change. From the point of transfer direction, conversion from farmland, forest land, resident land, unused land to grassland shows that initial result of local returning farmland to forest and grassland have been achieved, but conversion from grassland to unused land, which results in significant increase of unused land, shows that partial deterioration of desertification make the desertification control a long way to go. In oasis, increase of saline-alkali land coming from beach, gobi and farmland, which show seriousness of land salinization, should not be ignored in oasis construction. Overall LUCC is not as same as that in different time periods, along with relative fluctuation.(4)Through principal component analysis, local desertification factor is integration of natural factor and human factor. Natural factor include climate, soil and so on. Human factor include excessive population, excessive reclaim, overgrazing, unreasonable water resource use and policy mistake. Because of bad nature condition, self-reversal’s possibility of desertification of arid desert is very small so that human being must take powerful measure to control desertification.(5) South Ordos pleatu was taken as a example to research near future desertification dynamics. From 1991 to 2004, non-desertification area maintained invariable. Mild desertification reduced largely. Moderate desertification and severe desertification increased. Simultaneously different desertification degree transformed frequently each other, and patch complexity of severe desertification reduced. The above result indicated that desertification degree of study area was being weaken, and the present desertification degree is in the moderate desertification. The primary cause which influence vegetation coverage has two points:First, natural factor, for example, increase of rainfall is advantageous to vegetation restoration and has lagging effect. Second, human factor, desertification control measures have improved local ecological environment positively. Moisture and vegetation in semi-arid area are fairly better than that in arid area. If human disturbance were eliminated, desertification would have self-reversal possibility, but the reversal would have repeatability.更多还原