【作者】 张勇；

【导师】 乌兰图雅；

【作者基本信息】 内蒙古师范大学 ， 自然地理学， 2008， 硕士

【摘要】 沙漠化是荒漠化的主要类型,它作为极其重要的环境和社会经济问题正困扰着当今世界,威胁着人类的生存和发展。植被盖度是影响土地荒漠化的重要因子,是植物群落覆盖地表程度的一个综合量化指标,易于观测,并与土壤的水土流失、土地沙漠化关系密切。科尔沁沙地地处我国北方农牧交错带东段,属季风气候边缘区,具有典型的环境敏感性和脆弱性,很长时间以来,也是我国发生发展的典型区。但自20世纪末沙地出现了土地沙漠化的整体逆转,成为了我国从沙地中的环境改善之例。鉴于此,本文以沙地的典型区科尔沁左翼后旗为例,在对当前植被盖度测算方法的分析与研究的前提上,基于土地覆盖分类运用亚像元模型中的低密度模型对科尔沁左翼后旗1989年、2000年和2007年三个时期的植被覆盖度变化情况进行了定量分析,拟找出近20年来沙地土地沙漠化的趋势及其特征,进而分析沙漠化逆转的最根本原因,从而为今后沙地环境改善和生态保护提供科学的决策依据。通过研究发现:1.应用亚像元模型对科左后旗的植被覆盖度进行监测,经验证平均精度达到76%,实践证明该方法适用于科左后旗植被覆盖信息的提取。该方法可为沙区大范围植被覆盖度估算提供一种有效途径,基本能够满足生态及气候模型研究的需要;2.科左后旗2007年植被覆盖度等级的空间分布格局是:高植被覆盖主要分布在科左后旗东部的沿辽平原农业区和位于旗西南的大青沟自然保护区,中植被覆盖在科左后旗植被覆盖类型中占相当大的优势,分布比较广泛,几乎遍布全旗,低植被覆盖主要分布在中西北部沙丘沙地牧林区,无植被覆盖比较少,在全旗有零星分布,分布的主要位置是在位于西北部沙丘沙地牧林区的一些流动沙丘和湖泊等区域。从面积来说,2007年科左后旗的中植被覆盖占绝对优势,其所占的比例为72%,高植被覆盖19%,低植被覆盖8%,无植被覆盖所占的比例为1%;3.科左后旗的植被覆盖变化是复杂多样的,各个类型之间在不断的相互转化。1989—2007年近20年期间,有高植被覆盖和中植被覆盖两个类型的面积发生了波动,高植被覆盖从1989年的721km~2减少到2000年的644km~2,但是在2000—2007年期间,面积增长幅度比较大,增长到了2140km~2;中植被覆盖正好相反,先由6455km~2增加到9126km~2后减小到了8277km~2。高植被覆盖类型先减后增,中植被覆盖类型先增后减。其它各植被覆盖类型面积的变化都呈持续性减少变化。在空间分布上,植被覆盖强烈提高的区域主要集中在科左后旗的中西北部沙丘沙地牧林区和南部浅丘甸农林牧区,轻度提高分布比较广泛,几乎遍布全区域,轻度降低主要分布在东部的沿辽平原农业区,强烈降低的区域比较少,只有零星分布;4.1989年到2000年再到2007年,科左后旗植被覆盖等级的空间景观格局变化特点是:无植被覆盖和低植被覆盖的优势度在持续降低,而高植被覆盖在持续增大,中植被覆盖则先是明显增加,然后是略微减少,植被覆盖等级的多样性指数的计算结果,反映科左后旗植被覆盖处于变化发展阶段;全旗整体表现为先规整后破碎的特点,全区的斑块数先减少后增加,由1989年的256252块减到2000年的173860块又增到2007年的196908块。两时间段虽变化趋势不一致,但从各植被覆盖类型的面积变化情况反映出该区的生态环境是在逐步好转;5.通过对1989到2000年,以及2000年到2007年两个区间的植被覆盖变化情况分析,可以看出科左后旗植被覆盖的变化是受自然因子和人文因子共同作用决定的,但发挥主导作用的是人文因子。科左后旗生态环境建设仍将是一项长期而艰巨的任务。更多还原

【Abstract】 Sandy desertification is the main type of the desertification, it is extremely as the important environment and socio-economic problems of plaguing the world today, and threat to human survival and development. Vegetation coverage is the important factor that influences the land desertification , it is a comprehensive evaluation index that describe the plant community to overlay the earth’s surface , be easy to observe, and turn a close relation with the soil erosion , water losses and the land desertification. The Horqin sandy land is at the east of northern agro-grazing ecotone in our country, belonging to the monsoon margin areas, and having typical model of the environment sensitivity and vulnerability. For a long time, it was a typical area of the development of desertification in China. But since the end of the 20th century sandy desertification in the overall reversal, had once again become China’s sandy land from the environmental improvement of the cases. In view of this, this paper took a typical sandy area Keerqinzuoyihouqi as an example.With the analysis and research the calculate method of the vegetation coverage , this paper showed the quantitative analysis of 1989,2000 and third period in 2007 of vegetation coverage in the Keerqinzuoyihouqi with the method of sub-pixel model for vegetation coverage estimation based on land cover classification, and prepared to find out the trend of sandy land desertification and its characteristics in recent 20 years, then analysisd the most fundamental reasons of the desertification reversing, so as to improve the environment and provide a scientific decision making for ecological protection for future. Through the study found that:1.Used sub-pixel model to monitor the vegetation coverage of the Kezuohouqi,and mean precision validation of the extraction results was 76%, practicing to express that method can be used in the extraction of vegetation coverage in Kezuohouqi. That method could take an effective way for the sandy area’s vegetation coverage estimation, to meet the basic demand of the ecosystem and the climate model research;2. The vegetation coverage levels of Kezuohouqi in 2007 was that: the type of high coverage was mainly in the eastern part and in the southwest of the Daqinggou Nature Reserve, the type of medium coverage had a great advantage and a broader distribution, the type of low coverage mainly located in the northwest, and the type of no coverage mainly located at the northwest and the number of mobile sand dunes and lake areas. From the area, the type of medium coverage covered in the absolute superiority, its shared of 72%, the type of high coverage shared of 19%, the type of low coverage shared of 8% and the type of no coverage shared of 1%;3.The vegetation coverage of Kezuohouqi was complications and diverse, of each type at continuously of convert mutually. In the recent 20 years from 1989 to 2007, the type of high coverage decreased 721km~2 to 644km~2 from 1989 to 2000,but increased 2140km~2 from 2000 to 2007. The type of medium coverage increased 6455km~2 to 9126km~2 and then decreased to 8277km~2 .The other types area of the varieties kept on decreasing variety. In the spatial distribution, the vegetation coverage of the strong increase mainly concentrated in the region of the north-west and south , Mild increase almost throughout the entire region, mild decreased mainly in the eastern part , strongly reduced the relatively small region;4.From 1989 to 2000 and again to 2007, the space landscape change of Kezuohouqi’s vegetation coverage grade was that the index dominance of the type of no coverage and low coverage keep on decreasing, but the type of high coverage kept on increasing, and the type of medium coverage was first increased obviously and then decreased slightly; the calculation results of the vegetation coverage rating’s diversity index showed that Kezuohouqi’s vegetation coverage is in the variety development stage; The whole region performanced the features that first standardization and then crusher, The spot number of the region decreased first and then increased, from 256252 patches in 1989 decreasing to 173860 patches in 2000 and then increasing to 196908 patches again in2007. Although the variety trend inconformity in the two time segment, the area variety circumstance of each type of vegetation coverage showed an ecosystem environment of that area was turning for the better gradually.5.With the analysis of vegetation coverage variety circumstance in the two segments, one was from 1989 to 2000 and the other was from 2000 to 2007, we could see that the natural factor and the humanities factor played the common role to decide the Kezuohouqi’s vegetation coverage variety circumstance, but the humanities factor played a leading role. The ecological environment construction of the Kezuohouqi will still be one long-term and the arduous duty.更多还原