Knowledge Resource Center for Ecological Environment in Arid Area
| 农田土壤水力特性空间变异及其尺度效应 | |
| 其他题名 | Spatial variability and scaling effects of soil hydraulic properties in cropland |
| 舒乔生 | |
| 出版年 | 2008 |
| 学位类型 | 博士 |
| 导师 | 刘作新 |
| 学位授予单位 | 中国科学院沈阳应用生态研究所 |
| 中文摘要 | 土壤水力特性的空间变异和尺度效应近年来受到广泛关注。本研究以半干旱区(辽宁省阜新县)大片农田(面积20hm2)为对象，根据土壤物理性质拟合持水特性的转换函数，应用地统计学定量化持水特性的空间变异特征，并将多重分形和小波理论相结合，从奇异性和分辨率的角度探讨水力特性的尺度效应。\n采用基于3级土壤颗粒的线性回归(MLR3)、非线性回归(ENR3)和基于7级颗粒的线性回归(MLR7)等3种方法拟合土壤持水特性的转换函数，并评价它们描述空间变异特征的效率，结果表明：详细颗粒模型比简单颗粒模型精度更高，非线性回归亦能提高一定的预测精度；对半方差函数来说，线性回归的结构性方差大(结构性较好)，非线性回归结构性较差，详细颗粒不能增加结构性方差，因此精度高的转换函数不一定能更好表达水力特性的空间异质性。\n采用多重分形方法分析了水力特性基于奇异性的多重尺度规律，结果表明：导水率、有机碳含量、粘粒含量、萎蔫系数、VG参数α和θr有多重分形特征，其它特性为单一分形；水力特性与物理性质之间的关系在单一尺度和多重尺度下会产生较大的变化，这是因为影响它们之间关系的因素随之发生了变化。\n应用小波分析揭示出水力特性基于分辨率的尺度规律，结果表明：水力特性的波谱能量(方差)具有尺度和空间位置的依赖性；物理性质与水力特性之间的相关性随尺度变化而变化，仅在一定尺度(分辨率)上有效，且这种关系依赖于空间位置。尺度效应的研究对空间变异的取样具有一定指导作用。 |
| 英文摘要 | Broad interests are concentrated in spatial variability and scaling effects of soil hydraulic properties lately. By sampling from cropland in semiarid area (Fuxin, Liaoning), pedo-transfer functions of water retentions were developed with soil physical characteristics, and their spatial variabilities were quantitatively analyzed using geostatistics. Moreover, scale effects of hydraulic properties and scaling relationships between soil hydraulic properties and physical characteristics in terms of singularity and resolution were characterized by combination of multifractal and wavelet analysis.\nThree types of pedo-transfer functions (PTFs) were estimated using linear regression (MLR3) and nonlinear regression (ENR3) based on three textural classifications, and using linear regression (MLR7) based on seven textural classifications. In addition, their abilities to quantify spatial heterogeneity of soil water retentions were evaluated. It showed that water retentions from MLR7 and ENR3 were closer to measured values than ones from MLR3, suggesting that some complex mathematical approaches such as nonlinear regression or detailed soil classification might obtain more accurate PTFs. When semi-variance was considered, larger ratio of structure variance occurred for linear methods, while nonlinear ones had little structure because of higher stochastic errors. Moreover, detailed soil textual classification didn’t improve structure of variability. This indicated that pedo-transfer functions being closed to the measures in traditional statistics did not always express best the spatial structure or spatial heterogeneity of the data in geostatistics. \nThe multifractal analysis was applied to analyze the singularity-based multiple scaling rules of soil hydraulic properties. It showed that saturated hydraulic conductivity, organic carbon and clay content, wilting point, parameters α and θr in van Genuchten Function had multifractal properties, while other parameters showed mono-fractal ones. The relationships between hydraulic properties and physical characteristics changed when single or multiple scales are considered, respectively. Some physical characteristics significantly correlated to some hydraulic parameters at one scale maight not reflect spatial variability of the parameters at other scales or at multiple scales for different impact factors. This was because the impact factors controlling their relationships changed with scales. \nIn addition, resolution-based scaling laws of soil hydraulic properties were revealed by wavelet analysis. The results showed that the spectrum power of hydraulic properties had scale and location dependence. The relationships between hydraulic properties and physical characteristics also changed with scales, different even opposite relationship when scales were contracted or enlarged. Moreover, the scaling relationships were also location-dependent, embodying that the correlations between hydraulic properties and soil physical characteristics were negative for some locations and positive for other locations. It indicated scaling effects of soil hydraulic properties can guide to the sampling methods of spatial variability. |
| 中文关键词 | 土壤水力特性 ; 空间变异 ; 尺度效应 ; 多重分形 ; 小波分析 |
| 英文关键词 | soil hydraulic properties spatial variability scaling effects multifractal analysis wavelet analysis |
| 语种 | 中文 |
| 国家 | 中国 |
| 来源学科分类 | 土壤学 |
| 来源机构 | 中国科学院沈阳应用生态研究所 |
| 资源类型 | 学位论文 |
| 条目标识符 | http://119.78.100.177/qdio/handle/2XILL650/286671 |
| 推荐引用方式 GB/T 7714 | 舒乔生. 农田土壤水力特性空间变异及其尺度效应[D]. 中国科学院沈阳应用生态研究所,2008. |
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