导　　师： 李光录;张青峰

学科专业： 070503

授予学位： 硕士

作　　者： ;

机构地区： 西北农林科技大学

摘　　要： 地表糙度是影响土壤侵蚀过程的重要因子之一，也是土壤侵蚀学科领域研究的热点问题，探讨微尺度下（2cm×2cm）地表糙度在侵蚀过程中的空间异质性规律，对进一步理解土壤侵蚀过程和机理具有重要意义。为此，本文以黄土高原不同耕作措施条件下（4种常见的农业耕作措施：人工锄耕、人工掏挖、等高耕作、对照）的坡耕地为研究对象，通过进行固定雨强（60mm h-1）下不同坡度的室内人工模拟降雨实验，利用激光扫描仪获取地表糙度数据，运用地统计学和分形维数相结合的方法对地表糙度的空间分布特征及变异性进行研究。该研究结果为揭示微地形条件下地表糙度异质性对土壤侵蚀的作用与影响，并为黄土区进行有效的水土保持工作提供科学依据。主要结果如下： （1）基本统计特征分析表明：黄土坡耕地地表糙度在整体上的分布较均匀，具有较弱的空间变异性。其中，从不同坡度来看，表现为：5°＞10°＞20°＞15°＞25°，说明随坡度的增加，地表糙度的空间变异性逐渐减弱；从不同耕作措施来看，表现为：AD＞CT＞AB＞CK，表明AD坡面相比其他坡面具有较强的空间变异性。此外，不同耕作措施坡面对降雨侵蚀具有一定的抑制作用，这种抑制作用总体上表现为：AD＞CT＞AB。由此得出，AD耕作坡面为黄土区水土保持效应较好的坡面。在不同侵蚀阶段，地表糙度的变异性差别不大，表现为BR＞SpE≈ShE≈RE，表明降雨侵蚀对地表糙度具有一定的削弱作用。 （2）半方差函数分析表明：地表糙度的空间异质性主要由结构方差构成，且均表现出中等以上的空间自相关性。其中，AD坡面的自相关性在各降雨侵蚀阶段均表现为强烈的空间自相关特征；相较而言，5°坡的空间自相关性更加明显，其次为15°和25°坡，而不同坡面在降雨阶段的自相关性整体上并未表现出较为明显的规律，这说明人为耕作、坡度对地表糙度的影响远大于降雨对其的影响。 不同耕作措施、不同坡度坡面的自相关范围（变程）并不相同。总体上来看，微地形尺度的变程为2.42m。从不同耕作措施来看，AB坡面为3.59m，表明AB坡面的空间连续性较好，在2cm×2cm的研究尺度下其空间变异性并不明显，有待更小尺度的研究。AD、CK坡面的有效变程差异较小，分别为2.33、2.21m，表明其生态过程在相同尺度上起作用。CT坡面的变程最小，为1.54m，表明CT坡面的空间连续性较差，在以后的研究中应取更小的采样间距；从不同坡度来看，5°、10°、15°、20°、25°坡面的变程分别为2.05、2.52、3.82、1.68、2.02m。 （3）分形维数分析表明：黄土坡耕地地表糙度具有良好的分形性质，在研究的标度范围内并不是完全随机的，其分形维数在1.59～1.91之间，整体表现为CK/(1.742/)ShE/(1.76/)＞RE/(1.75/)，表明随侵蚀的发展，各坡面在小尺度上的变异逐渐减弱，空间异质性逐渐减弱，而大尺度上的变异逐渐增强并控制着地表糙度的配置格局。 （4）各向异性分析表明：不同水蚀过程中，黄土坡耕地地表糙度的半方差函数均具有明显的方向性，表现为在90°和135°方向上表现为各向同性，地表糙度的空间异质性变化一致。在0°和45°方向上的各向异性比大于1，表现为各向异性。 （5）空间自相关分析表明：从不同耕作措施来看，随采样间距的不断增大，黄土坡耕地地表糙度的空间自相关呈正负交替现象，各坡面空间结构特征的复杂性表现为CT＞AD＞AB＞CK，这正好和分形维数所得的结果相吻合。总体上在0-10cm的变程范围之内，地表糙度表现为明显的空间正相关或负相关，表明在这个变程范围之内，地表糙度的空间异质性受随机性因素和结构性因素的共同作用，这与半变异函数分析的结果相一致。 （6）Kriging插值分析表明：黄土坡耕地地表糙度的空间分布具有明显的斑块状或连续分布的特点。从不同坡度来看，20°坡面地表糙度的空间分布较复杂，在图中呈现明显的斑块状分布，且差异明显；从不同耕作措施来看，CT坡面地表糙度的空间分布较复杂，呈现明显的条带状及斑块状分布状况，表明坡度、耕作措施均会对地表糙度的变化产生影响。 Surface roughness is one of the most important factors to affect soil erosion process,which is also the research hotspot in soil erosion science. Study the spatial heterogeneity ofsurface roughness of4typically loess tilled slopes during different erosive stages under amicro-scale /(2cm×2cm/) condition is significant for further understand the process of soilerosion. When slopes with4different gradients and tillage measures were prepared /(artificialbackhoe, artificial digging, contour tillage and check/), a erosive rainfall under a rainfallintensity of60mm//h was carried out. Soil surface roughness relative elevation data pointswere taken by a laser scanner and analyzed with both the semivariogram function and fractaldimension models. It can promote understandings and quantitative description of the couplingrelationship between the surface roughness and erosion, and it also can provide a theoreticalbasis to guide future tillage practices in the loess sloped regions /(1/) The results of classical statistical analysis showed that: The loess tillage slope surfaceroughness has a weak spatial variability. Which, the variability of the different slope was inthe order5°＞10°＞20°＞15°＞25°, With the increase of gradient, the spatial variability ofslope surface roughness tends to weaken; The variability of the different loess tilled was in theorder AD＞CT＞AB＞CK, it showed that AD slope has strong spatial variability than othercultivation measures slopes. In addition, different tillage measures slope for rainfall erosionhas certain inhibition, this inhibitory effect was in the order AD＞CT＞AB generally. Thus,AD farming slope has the good effect of soil and water conservation in loess area. In differentstages of erosion, the variability of surface roughness showed BR＞SpE≈ShE≈RE, and itindicated that rainfall erosion weakens the surface roughness. /(2/) The results of the semivariogram analysis indicated that the loess tilled slope surfaceroughness has a higher spatial autocorrelation, their spatial autocorrelation scale of surfaceroughness range from2.02m to3.59m. Which, the spatial autocorrelation of AD slopesurface in each rainfall erosion stage are characterized by strong spatial autocorrelationcharacteristic; the spatial autocorrelation of the different slope was in the order5°＞15°＞25°,but on the whole, the spatial autocorrelation of different rainfall stage did not show moreobvious regularity, this suggests that the artificial cultivation, the influence of the slope of thesurface roughness is greater than the influence of the rainfall. Different tillage measures, different slope slope surface from the relevant range is not thesame, seen from the point of different tillage measures, the spatial autocorrelation of AB slopeis3.59m, show that AB slope surface space continuity is better, the studies in2cm×2cmscales its spatial variation is not obvious, it needs to be studied more small scale. The effectiverange difference of AD slope and CK slope is small, effective, respectively2.33,2.21m,show that the ecological processes works on the same scale. The spatial autocorrelation of CTslope is1.54m, indicate that CT slope surface space continuity is worse, in future studiesshould take smaller sampling interval. From the point of different slope, The range of5°,10°,15°,20°,25°slope surfacewere2.05,2.52,3.82,1.68,2.02m. Overall, micro scale variation of terrain is2.42m. /(3/) The fractal dimension analysis results showed as follows: The loess tilled slopesurface roughness has good fractal features. In the research of scale range, it was notcompletely random, and it ranged from1.59to1.91. Its fractal features was in the orderCK/(1.742/) SpE /(1.77/)> ShE/(1.76/)> RE /(1.75/), suggested that along with the development of the erosion, the variation ofthe slope weakened on a small scale gradually, its spatial heterogeneity is more weaken, thespace configuration pattern of surface roughness is mainly controlled by variation in a largerscale range. /(4/) The anisotropy analysis results showed as follows: In the different process of watererosion, semivariance function of loess slope surface roughness has obvious directivity, showit is isotropic on the direction of90degrees and135degrees, the change of surface roughnessis consistent. On the direction of0degrees and45degrees, the semivariance function of loessslope surface roughness is anisotropic. /(5/) The spatial autocorrelation analysis showed that: From the point of different tillagemeasures, with the sampling spacing increasing, the spatial autocorrelation of the loess tilledslope surface roughness is plus or minus alternate phenomenon, the complexity of the spatialstructure of the slope was in the order CT＞AD＞AB＞CK, the results agree fairly well withthose obtained by the fractal dimension analysis. Overall, within the variation range of0to10cm, and the surface roughness show significantly positive spatial autocorrelation or negative spatial autocorrelation, this show that within the variation, The spatial heterogeneity ofsurface roughness was affected by random factors and structural factors work together, theresults agree fairly well with those obtained by the semivariagram analysis. /(6/) The results of kriging interpolation analysis showed that: The spatial distribution ofthe loess tilled slope surface roughness has the characteristics of obvious plaques orcontinuous distribution. Seen from the point of different slope, in the20degrees slope, thespatial distribution of the surface roughness is more complex, and present obvious patchshape distribution, and the difference is obvious; Seen from the point of different cultivationmeasures, in the CT slope, the spatial distribution of the surface roughness is more complex,and present obvious banded and patch shape distribution, shows that slope, cultivationmeasures will affect the change of surface roughness.

关 键 词： 黄土高原 坡耕地 地表糙度 空间异质性 半变异函数 分形维数

分 类 号： [S157.1]

领　　域： [农业科学] [农业科学]