【作者】 张芳；

【导师】 熊黑钢；

【作者基本信息】 新疆大学 ， 自然地理学， 2011， 博士

【摘要】 盐渍土是指一系列受土体中盐碱成分作用的、包括各种盐土和碱土以及其他不同程度盐化和碱化的各种类型土壤的统称。新疆是我国土壤盐渍化面积最大的省份,程度重,类型多,有“世界盐碱土博物馆”之称。土壤盐渍化已成为绿洲——这一新疆人民赖以生存空间土地的主要退化原因之一。因此土壤盐渍化问题一直是新疆干旱区环境改善及可持续发展的战略问题和热点研究领域。碱化土与盐化土属于不同的土类,具有不同的理化特性、表现特征和发生发展机理。目前学者们的研究多集中于积盐严重的南疆地区,对于天山北坡大面积存在的碱化土壤研究较少。本文通过大量的野外调查与定点土壤、光谱、植被样本采集,以地理学、土壤学、环境学、生态学及遥感学理论为基础,以3S技术为手段,采用定性与定量相结合的方法,对奇台绿洲碱化土壤的理化特征、土壤碱化与环境因子的耦合关系、土壤碱化强度、不同尺度光谱对碱化土壤的响应以及碱化土壤的遥感监测进行了系统的探讨。在论文的第一章主要介绍了研究碱化土壤的目的、意义,总结了国内外对碱化土壤的研究进展,阐述了研究思路、研究内容及采用的技术方法。第二章对研究区概况、野外考察、数据采集及样本处理过程进行了详细说明。第三章在对土壤碱分进行实测分析的基础上,探讨了研究区碱化土壤的理化性质,并利用SRTM数据提取的地形信息研究了基于区域尺度地形因子的碱化土壤空间分异规律。第四章讨论了盐（碱）生植被盖度与各个土壤碱化指标的关系,分析不同土壤碱化程度对植物生长的影响,建立了基于盐（碱）生植被盖度的土壤碱化分级。第五章着重分析了端元、材料、像元三种不同尺度光谱反射率与土壤pH值之间的关系,进行了不同尺度的光谱转换,建立了碱化土壤的定量遥感监测模型。第六章对整个研究过程、主要成果和进展进行了概括和总结。主要研究成果与结论如下:（1）研究区土壤碱化强烈,土壤pH均值超过8.8,属苏打碱化土。研究区土壤碱化与盐化并存,在研究区西北角临近沙漠边缘的小范围区域内仍有积盐现象。区域尺度上,地形对当前碱化土壤空间分布格局起着主要作用,东南部高于740m高程的陡坡区为碱化区,西北角低于680m高程的缓坡区为积盐区,中间为脱盐碱化区。pH值随着海拔高度的上升而增加,盐分则随着海拔高度的增高而降低,碱化和盐化的演化趋势具有明显的相逆特征。高程与大部分碱（盐）指标呈极显著相关关系,其对碱、盐程度及各离子空间分异的影响大于坡度。（2）盐（碱）生植被盖度与土壤各碱化指标均呈极显著的负相关关系,其与土壤pH值的相关系数最高,达0.810,其次为钠碱化度ESP。土壤碱化程度是影响盐（碱）生植被盖度的主要因素,盐（碱）生植被盖度对土壤碱化强度具有良好的指示作用。基于盐（碱）生植被盖度并结合土壤碱化指标,建立了研究区的土壤碱化分级标准。该标准既符合研究区实际特点,也与国内外其他土壤碱化分级具有良好的对应。（3）分析碱化土壤的端元、材料及影像光谱响应特征并进行了相应的尺度转换。裸土的端元光谱与影像光谱拟合关系良好,R²可达0.9627,但其与材料光谱的转换模型则相对复杂。利用回归分析方法分别建立了基于端元反射率和影像反射率的土壤碱化预测模型,二者对研究区以板结为特征的碱化土壤均具有良好的监测潜力。其中,端元反射率建模精度最高,多波段回归预测模型的判定系数R²为0.873,可以快速、高精度地对土壤碱化程度进行估算。植被对TM影像反射率预测精度的影响较大,直接用TM反射率预测pH值精度不如端元反射率理想。材料光谱与土壤有机质关系良好,但与碱化土壤之间没有明显的相关关系。碱化程度对野外实际环境中土壤表面性状的影响是土壤碱化遥感监测的重要依据。（4）通过对碱化土壤的不同尺度光谱响应的对比分析,构建了基于pH-NDVI特征空间的土壤碱化遥感监测指数pHI。该指数对碱化土壤的提取精度达94%。pHI指数图像提取的pH值与实测值吻合较好,平均误差0.25个pH单位。利用pHI对研究区碱化土壤进行提取应用,弱碱化土和中度碱化土占荒地面积的84%,其中pH8.0～8.5的弱碱化土中游离的碱性盐Na₂CO₃和NaHCO₃较少,易于进行改良利用。如果能够解农业供水问题,该区耕地开发的潜力很大。更多还原

【Abstract】 Saline-alkali soil is a general designation of a series of soil which is affected by saline-alkali components and includes all kinds of saline soil, sodic soil and soil with different degrees of alkalization and Salinization. Xinjiang has the largest area of saline-alkali soil hence is called as“the saline-alkali soil museum in the world”. Soil alkalinization and salinization have already become tone of the major land degradation reasons in oasis, the only land for the people to live in Xinjiang. The problem about soil alkalinization and salinization is also an issue related to the regional sustainable development and the environment improvement in Xinjiang’s arid areas. Hence soil alkalinization and salinization have always been a focused research field. Alkali soil and salty soil have different chemical and physical properties, land surface symptoms, occurrence and development mechanism, therefore they belong to different soil types. So far, in Xinjiang, studies on the soil salinization and alkalinization mostly focuson southern areas where salt is significantly accumulated in topsoil but very few on larger areas of alkalinized soil in the Northern Slope Area of Tianshan Mountain in XinjiangBased on a large number of field investigations and soil, spectrum and vegetation samples collected from given spots, as well as the application of geography, agrology, environmentology, ecology and remote sensing theory, this thesis systematically discusses the physical and chemical characteristics of alkalinized soil, the correlations between soil alkalinization and environment factors, the subdivision of degree of soil alkalinization, the characteristic s of spectra of alkalinization soil in different scales and the investigation by remote sensing on the alkalinized soil in Qitai Oasis in Xinjiang by the 3S techniques and quantitative and qualitative method s.The first chapter mainly introduces the background and the purpose of the soil alkalinization study summarizes the domestic and international advances of soil alkalinization research, and then demonstrates author’s research concepts, research contents, research procedures and methods in detail. The second chapter primarily introduces general situations of the study area, and specifies the procedures of field investigations, data collection and sample tests. The third chapter discusses soil physical and chemical properties in the study area, investigates into the distribution of the alkali -saline soil and the correlation between this spatial pattern and the topographic factor extracted from SRTM data and analyzes the spatial variation and distribution based on the regional topographic factor using the data from monitoring the soil alkali content in Qitai oasis. The fourth part studies the relationship between halophyte coverage and soil alkalinization indices and builds the subdivision of the degree of soil alkalinization based on the restraining effect on halophyte from different levels of soil alkalinization. The fifth part focuses on the correlation between soil pH and spectrums in three different scale （field-measured spectrum,laboratory-measured spectrum and the image spectrum）. A new quantitative remote sensing monitoring index pHI for soil alkalinization is built. The last chapter summarizes the whole thesis and lists the achievements, difficulties and prospect s of this study.Main conclusions and developments as follows:（1） Alkaline-earth in the study area presents a typical desalination-alkalinization feature. The average value of soil pH is more than 8.8, and the soil within the study area is belong to sodic alkali soil. The alkalinization and salinization of soil occurs simultaneously in the study area because a small area near the Gurbantunggut Desert still has the phenomenon that salt is being accumulating in topsoil.At a regional scale, topography plays an important role in the spatial distribution of the alkali -saline soil, and salt is accumulated within the slightly sloped area below the elevation of 680m. Alkalinization occurred in the steeply sloped area above 740m. With the altitude decreasing, the soil salt content increases and the PH value drops concurrently, so the evolvement of salination has a reversal pattern as alkalinization. Elevation has more impact on the soil salinization-alkalinization degree and the spatial distribution of ions of salt compared with slope.（2）There is a significant negative correlation between halophyte coverage and each soil alkalinization index. The correlation coefficient between halophyte coverage and soil pH is the greatest of 0.810 and the next highest is ESP. Soil alkalinization is the major restrained factor to halophyte coverage; therefore halophyte coverage could be a good indicator of the soil alkalinization level. Based on halophyte coverage, the subdivision of the degree of soil alkalinization is built and the degree standard has good response to other soil alkalinization degree standards in domestic and overseas.（3）Both the filed-measured reflectance and the image reflectance multivariate linear regression models were built to the evaluate soil alkalinization level. Filed-measured reflectance had good potential ability to rapidly and accurately estimating changes of the soil alkalinization and the model obtained the best effect with a R² of 0.873. If building model by TM reflectance directly, the accuracy of fitting is lower than the model of the filed-measured spectrum because of the vegetation distraction in the image spectrum. The Laboratory -measured spectrum is significantly negatively correlated to the soil OM, but not correlated to the soil pH.（4）From the analysis and comparison of the response characteristics of the spectrums in three different scales （field-measured spectrum,laboratory-measured spectrum and the image spectrum） of alkalinized soil, pH-NDVI space-based remote sensing synthesis index models for monitoring soil alkalinization was built. The result of extracting alkalinized soil shows a high accuracy of 94% by pHI method. The extracted pH from the image by pHI is in good agreement with the measured soil pH with the average error of 0.25 pH unit. The application of extracting alkalinized soil in the study area based on pHI covers the area of lightly alkalized soil and medium-alkalized soil that represent 84% of the total wasteland. The lightly alkalized soil with pH8.0～8.5 has little free Na₂CO₃ and NaHCO₃ , so it is easy regarding to improvement and utilization. If irrigation water supply problem can be solved, Qitai oasis will has great potential in ploughland developments.更多还原