【作者】 王若凡；

【导师】 南忠仁；

【作者基本信息】 兰州大学 ， 环境科学， 2013， 博士

【摘要】 干旱区绿洲是以荒漠为基质、围绕绿洲构成的特殊生态系统,绿洲景观因为荒漠基质的包围而具有封闭性,且长期受干旱气候制约,显示出较明显的生态脆弱性。近年来随着人口增加,人们也逐渐意识到合理利用、开发干旱区绿洲的资源的重要性及其与社会经济可持续发展的制约关系。如何稳定干旱区的绿洲生态系统是干旱区生态环境保护的核心问题,这不仅要有宏观管理的战略,更需要相应的技术体系支撑管理决策的制定。鉴于此,本研究在景观生态学原理基础上,采用GIS技术构建了干旱区绿洲生态风险评价体系。该技术体系能够评估人类干扰及自然因素对干旱区绿洲生态系统结构、功能及生态价值产生不利影响的可能性和大小。结果能够直观表达该影响在时间序列的变化及空间上的分布。具体来说本研究包括两方面内容：(1)评估技术体系构建本文基于美国生态风险评价框架,建立了干旱区生态风险评价框架。这一框架不仅能体现干旱区生态风险评价的基本内涵,又能作为干旱区生态风险评价开展的技术指导路线。在上述框架基础上,本文进一步构建了干旱区生态风险评价步骤及指标体系。评价步骤主要包括：风险管理目标的确立；多风险源与风险受体的指标体系建立；表征压力响应和暴露评价的概念模型；基于GIS技术的数据处理；风险评估结果定级和可视化的表达等5部分内容。(2)应用对比研究本文将建立的方法体系运用在甘肃省黑河流域的实例研究中。甘肃省黑河流域是甘肃省非常重要的内陆河流域,气候干旱,生态环境极端脆弱。而黑河流域(甘肃段)所在区域也是整个黑河流域体系中人口最为密集,因此受自然灾害及人类干扰共同影响最为明显的区域。运用本文构建的生态风险评价体系进行评价。评价结果表明,目前研究区域的生态风险水平为中等风险水平。从生态风险图来看,研究区域的生态风险水平的空间分布呈现出三个层次,以水域为核心的低风险-较低风险区,以荒漠与绿洲交接的中等风险区及与沙漠毗邻的较高-高风险区。而在过去十年间研究区域的生态风险值略有下降,从0.83下降到0.60。风险水平从高风险水平下降到中等风险水平。具体来说：①从压力指标来看,研究区域综合风险概率略有下降,从0.27下降到0.22。这得益于两个方面,一方面是人们已经注重对干旱区这一脆弱生态系统的保护,不断加大环境保护力度,表现为人为干扰指数(HAI)有所降低。另一方面,研究区域在过去十余年中自然气候条件有所改善,自然灾害发生的频率略有下降,表现为旱涝灾害指数(Fc)有所下降。②从响应指标来看,研究区域景观的结构指数呈下降趋势,表现为越来越不稳定,其稳定性指数从0.48下降到0.41。具体表现为景观的多样性增加、优势度下降、景观的破碎程度升高,体现出更不均一的特点。③结合生产力指标可以看出,随着研究区近年的光热条件的改善,并辅以退耕还林、还草等措施,研究区域的净第一生产力有所恢复,从0.67上升至0.94。最后可以得出结论,研究区域生态风险值不断降低,表现为光热条件不断改善,人为干扰不断下降,区域生态系统朝着更为良性的方向发展。若在这个时期对研究区域土地资源加以合理规划及合理利用,最终可以使研究区域生态朝着更为有利的方向发展。本文篇尾将本研究构建的方法体系与目前的生态风险评价的基本框架、区域生态风险评价的一般研究范式及干旱区的稳定性研究等前人的研究方法体系进行了对比研究。对比结果表明本研究构建的评估框架更具有指导意义；构建的概念模型更能体现干旱区绿洲生态系统的压力响应关系；基于GIS技术的评价方法更简便、更具操作性,可为干旱区绿洲生态系统的环境管理提供可量化的技术支持。更多还原

【Abstract】 Arid-oasis areas become even more critical as1/3of the Chinese population lives in arid-oasis regions in recent years. From long-term sustainable economic development point of view, it is important to build an eco-risk assessment method fit for assessing arid-oasis areas by using regional eco-risk assessment theory. Arid-oasis area has typical landscape types different from other eco-system. Oasis land degradated these years because of the long term human impacts and nature disaster, which is different from the city areas and developed areas. So the previous method and technical system could not be a guid to conduct the arid-oasis assessment. Based on landscape ecological features of arid-oasis area and by using3S. our study attempts to construct an eco-risk assessment technical system to assess the potential risk caused by natural disaster and human activities in arid-oasis areas. The technical system could assess the change in the time series and spatial distribution. Finally, we conducted a study on the eco-risk assessment in the Heihe River Basin, which is a typical arid-oasis ecosystem in China, to verify the feasibility, intuition and generality of the technical system.The study concluded following two parts:1) Construct a eco-risk assessment technical systemIn the theory research part, on the one hand, we modified the framework for eco-risk assessment conducted by the U.S.EPA, as a guidline to assess the eco-risk in arid-oasis areas. On the other hand, this paper constructed a eco-risk assessment technical system. The whole process is based on six major elements, the purpose of the assessment concerned by the risk manager and risk assessor, conceptual model characterizing risk and the assessment end point, tools of data procurement and data analysis, index system characterized the effects and the exposure, uncertainty analysis and final result of the eco-risk, including the change on the time series and the spatial distribution.2) Comparative study on the applicationTo verify the feasibility, intuition and generality of the technical system conducted in the front part, we did a case study on The Heihe River Basin. The Heihe River Basin is located at98°00- 101°30’E,38°00’-42°30’N and has a drainage area of130,000km2. It consists of the upper mountainous area, the Middle Oasis area, and the lower terminal arid Oasis-Gobi-desert area. This paper focuses on the middle Oasis area, including8counties, Jinta, Jiuquan, Jiayuguan, Gaotai, Linze, Zhangye, Shandan, Mingle. This area has the The highest population density and the typical area influenced by the human activities and natural disaster.In this case study, based on advanced remote sensing and Geographic Information Systems (GIS) technologies, the influences of precipitation, human activity and vegetation sensitivity are evaluated. The change of landscape index system could assess the eco-risk of The Heihe River Basin. The final value of eco-risk is classified into five levels: extreme low, low, moderate, high and extreme high. The results including:①The landscape eco-risk value (ERI) of the Heihe River Basin decreased from0.83to0.60, from the high-risk level down to the middle level. The results can be attributed to the better living conditions, the effective policy of environmental protection and effective Ecological Restoration over these years.②The spatial distribution could be divided into3regions, the high risk level region was influenced by the erosion of desert and water loss and soil erosion. For example, the northern area of the Heihe River Basin was in higher risk than other areas because where is next to the Badan Jara Desert and has been subjected to erosion due to scarce vegetation and serious water shortage in the past10years. The middle level region was influenced mainly by the human activities and natural erosion. The extreme low area was mainly influenced by the human activities.③The structure stability of landscape is decreased from0.48to0.41because of the decreasing landscape dominance and landscape diversity and increasing fragmentation.④The first net productivity index increased from0.67to0.94because of the better living conditions.⑤Finally, we can concluded that, from the results above, the eco-system of The Heihe River Basin Toward a more favorable direction In the final research, we conducted a comparative study. Our study showed that, the research method constructed in this study can objectively detect the spatial distribution of the landscape risk values in the arid oasis area and the time series change of the eco-risk. It could play a positive role in the future arid-oasis ecosystem eco-risk assessment and assist future environmental management.更多还原