【作者】 魏琦；

【导师】 唐华俊；

【作者基本信息】 中国农业科学院 ， 农业区域发展， 2010， 博士

【摘要】 我国北方农牧交错带不仅是联系和沟通农区和牧区的重要纽带,也是中、东部平原农区天然的生态屏障。在阻隔荒漠化南侵和涵养流向农区的江河水资源等方面都有其独特的不可替代的作用,在我国生态保护和改善中极为重要。在气候变化和人类活动加剧的驱动作用下,尤其是不合理利用自然资源甚至是破坏性利用(如过度放牧和滥垦滥采滥伐),我国北方农牧交错带正面临着越来越大的压力,许多地区承受的压力已超过了当地生态系统的承载能力,从而发生生态环境恶化现象。林西县是我国北方农牧交错带的典型地区,由于长期的过度放牧、垦荒和采矿,加上人口增长和城市化发展,生态问题比较突出。本文通过林西县的实证研究,探索我国北方农牧交错带生态脆弱性评价方法,定量确定林西县生态脆弱性程度,揭示林西县生态脆弱性形成的机制,阐明林西县生态脆弱性时空变化规律,系统总结和评价林西县退耕还草生态治理工程的经验、技术措施和成效,探讨林西县进一步开展生态脆弱性治理的技术体系和发展模式,为全县乃至周边地区的生态环境治理与建设、种植业结构调整及草地畜牧业持续高效发展提供重要科学依据。在研究的手法上,本项研究突破传统的以统计模型为基础的分析方法,把定量遥感技术应用到区域生态脆弱性评价的研究中,结合生态脆弱性评价模型,分析林西县生态脆弱性的时空发展变化特征和生态系统初级生产力的空间变化规律,同时,我们以林西县的生态治理实践为契机,在典型剖析的基础上,分析退耕还草还林工程实施对当地社会经济各方面的影响,评价生态治理工程的实施效果。本文从林西县实际出发,通过深入分析林西县生态环境问题,结合生态治理需要,从成因与表征两个方面选用了气候、地形、营力、经济发展等8个要素18个具体指标来构建林西县生态脆弱性评价的指标体系和指数模型。利用主成分分析确定各评价指标的相对权重,定量确定了林西县生态脆弱程度,提出了林西县生态脆弱性评价等级划分方法。从气候变化和人类活动等角度深入剖析了林西县生态脆弱性的形成机制；结合MODIS遥感定量分析,从植被指数和植被覆盖度两个方面分析验证了林西县生态脆弱性的时空变化规律及其与降水年际变化的关系。在此基础上,对林西县以退耕还草为主的生态治理技术措施与影响进行深入分析,为林西县继续深化生态治理提供技术支撑和理论依据,同时也积极探索我国北方农牧交错带生态脆弱性评价的技术方法,促进我国北方农牧交错带生态环境与经济社会可持续发展。文中以林西县为典型代表的我国北方农牧交错带生态脆弱性评价,可以划分为5个等级,依次分别为：微度脆弱、低度脆弱、中度脆弱、高度脆弱和极度脆弱。这5个等级对应的生态脆弱度指数(EVI)范围分别为：EVI低于25为微度脆弱,EVI在26-40之间为低度脆弱,EVI在41-55之间为中度脆弱,EVI在56-70之间为高度脆弱,EVI高于70为极度脆弱。我们的研究结果表明,目前林西县的生态脆弱度指数值为41.59,属于中度脆弱等级,且生态脆弱性存在明显的空间差异,中高度以上的生态脆弱区主要分布在中南部地区,微度和低度脆弱区主要分布在北部和生态条件较好的河谷地带。林西县植被指数和植被覆盖度不仅空间差异大,而且年际变化也很大,与降水量的年际变化有密切相关。2000-2009年间,林西县的全县平均植被指数NDVI值为0.59,最大值是2004年的0.68,最小值是2000年的0.42,高低相差达0.26。植被指数NDVI越大,表示绿色植被越多,因而也意味着生态系统越健康。2000-2009年间林西县全县平均植被覆盖度为0.63,最高是2004年,达到0.77,而最低是2000年,只有0.39,与最高的2004年相差达1倍。植被覆盖度的年际巨大振荡,说明生态系统比较容易受到降水等因素的变化影响,是脆弱性较大的表现。林西县近年来的退耕还草生态治理实践,形成了许多有效的生态治理技术体系。比较成熟的技术体系包括人工草地建植及持续利用,退耕地植被恢复重建,退化和沙化草地植被恢复,河滩盐碱地混播牧草地建植以及优良牧草种植繁育等。分别实施了干旱山区优质高产人工草地及饲料基地建植、低山丘陵区牧草种子生产基地建植和河谷平川区优质草产品高效生产基地建植技术措施,重点发展了寒旱区尖叶胡枝子栽培、沙化地柠条锦鸡儿栽培、退化耕地粮草混播人工草地建植、高寒区优质高产一年生牧草及饲料作物草地建植等技术措施,为进一步推进林西县生态治理的实践提供技术支撑。林西县生态治理实践,取得了很好的效果。退耕还草为主的生态治理对当地社会经济发展的促进作用较大,不仅增加了就业,拉动了地方经济,而且提高了农牧民人均纯收入水平。近年来林西县地方财政收入和农牧民人均纯收入增长很快,2008年与2000年相比,分别实现了57%和88%的涨幅。退耕还草工程对林西县种植业结构调整具有较大影响,人工草地建植不断增加,牧草占耕地面积的比重由过去的5.3%增加到25.0%,上升了近20.0%,经济作物占耕地的比重由原来的8.3%增加到13.3%,而粮食作物占耕地比重则相应地降低了24.7%。退耕还草生态治理工程还加强了林西县当地农牧区基础设施建设,提高了当地农牧民的经济发展和产业经营水平,带动了当地农牧业产业结构调整和生产经营方式转变,长远来看,是有效保障当地生态安全,降低生态脆弱性,协调生态-经济-社会发展的重要途径。通过项目实施,产业结构得到了合理的调整,农牧民生产经营方式有较全面转变,但是重点区域的草畜矛盾仍然比较突出。总之,本项研究采用遥感技术手段,根据植被在生态系统功能结构中的高度重要性,创造性地尝试从植被覆盖的角度来分析验证区域生态脆弱性评价结果,发展了生态脆弱性评价技术与方法,为进一步开展我国北方农牧交错带生态脆弱性评价提供技术支持。更多还原

【Abstract】 The agro-pastoral ecozone in northern China is not only an important link between agricultural and pastoral areas, but also an ecological protective belt for the eastern agricultural plain, playing an indispensable role in preventing the southward desertification and water conversation for rivers. Thus it is important for the ecological protection and improvement in China. Due to climate change and excessive use of natural resources, (such as overgrazing, and over-logging), the farming-pastoral zone in northern China is faced with more pressure than it can bear. Linxi county is a typical example in this area. Due to long-term over-grazing, wasteland reclaiming and mining, plus population growth and the urbanization, ecological problems in Linxi County become very prominent. Through empirical research, this paper explores methods to evaluation the ecological vulnerability in northern China, rating the frangibility of Linxi county, revealing its ecological vulnerability mechanism, explaining its characters in spatial terms, summarizing and evaluating experience, technical measures and achievements of the programs for ecological reclamation,and exploring technical system and development mode for ecological improvement. The study aims to provide scientific basis for the ecological development in Linxi County and its surrounding areas as well as the restructuring of cropping patterns and the long-term development of grassland grazing.In terms of methodology, this study adopts the quantitative remote sensing techonology other than the traditional statistical model in the evaluation of the ecological vulnerability in the area. It analyses the space-time characteristics and the special rule of primary productivity in ecological system in Linxi country. Meanwhile, through case study, it analyses the social economic impact of the ecological reclamation programs adopted in Linxi County and assesses its effect.This study analyses the environmental problems in Linxi County and establishes an indicator system and index model for the vulnerability evaluation in the county, in which 8 factors including climate, topography, force, economic development and 18 indicators are selected, covering the cause of formation and characterization of ecological vulnerability. We proposed the rating system for the ecological vulnerability in Linxi county, using the major component analysis method to determine the relative weight of each indicator, thus quantitatively determining the level of ecological vulnerability in the county. The formation mechanism of ecological vulnerability was analysed from the perspective of climate change and human activities. The relationship between the space-time characteristics of ecological vulnerability in Linxi county and the inter-annual precipitation was analysed from the perspective of vegetation index and vegetation coverage by use of quantitative MODIS remote sensing..On this basis, it further analysed the technical measures and impact of ecological management programmes in Linxi county, providing technical support and theoretical basis for further ecological management in the county. At the same time, it actively explores the assessment methods for ecological vulnerability in north china in order to promote the sustainable ecological environment and economic and social development in agro-pastoral ecozone of north china. The ecological vulnerability of the agro-pastoral ecozone in north China, as represented by Linxi County, was rated in 5 levels:mild, low, moderate, high and extreme vulnerability, respectively corresponding to the ecological vulnerability index (EVI):EVI that is below 25 is mild vunerability; between 26 and 40, low vulnerability; between 41 and 55, moderate vulnerability; between 56 and 70, high vulnerability and above 70, extreme vulnerability. Result shows that the ecological vulnerability in Linxi county is 41.59, falling into the moderate vulnerability category. Besides, the vulnerability demonstrates special characters, with the mid and south areas above the moderate level while the north and river valleys at the mild and low level.The vegetation index and the vegetation coverage rate in linxi is differenct in areas with great change every year, due to the change of annual percipatation. During 2000 to 2009, the average NDVI of Linxi county is 0.59, with the maximum value at 0.68 in 2004 and the minimum value at 0.42 in 2000. The gap is as large as 0.26. The higher the NDVI is,the more green vegetation there are and the healthier the eco-system is. During 2000 and 2009, the average vegetation coverage rate of Linxi County is 0.63 with the highest value at 0.77 in 2004, and the lowest value at 0.39 in 2000, only half of the maximum value. The huge inter-annual change of vegetation coverage rate shows that the eco-system is easily affected by the level of precipitation, which is clearly a sign of vulnerability.In recent years, Linxi county develops a ecological management system through many reclamation programs. Mature technical systems include artificial grass planting and its sustained utilization, restoration of vegetation on reclaimed land, the restoration of degraded and desertificated grassland, the grass planting on the saline beach and the breeding of excellent forage grasses. Linxi County also adopted some technical measures such as planting grass and fodder crops in the dry mountain areas, forage seed production in the low hill areas and grass products in the river valleys.Ecological management practive in Linxi County was quite successful. Returning farmland to grassland has played a positive role in local social economic development. It not only increased imployment, but also spurring local economy and raise the per capita net income of farmers and pasturers. In recent years, local revenue and per capita income of farmers have grown rapidly. Compared with 2000, the increase rate local revenue and per capita income of farmers were 57% and 88% respectively in 2008. Ecological reclamation projects has helped optimize the planting structure in Linxi County. Artificial grassland increased from 5.3% to 25.0%, which nearly rose by 20.0%. Cash crops increased from 8.3% to 13.3% while food crops decreased by 24.7%. These projects also help improve the agro-pastoral infrastructure in the County and promote industrial readjustment and shift of economic modeland. From the long term perspective, these projects are very important for eco-safety and the coordinated development of the eco-environment and social and economic development. However, the shortage of forage supply in this areas is still very severe.To summarize, this study adopts remote sensing technology to analyse the ecological vulnerability from the perspective of vegetation coverage according to the importance of vegetation in the ecological system. It develops the ecological vulnerability evaluation methods and techniques and provides technical support to further assessment of ecological vulnerability in northern China.更多还原