[Objective]Strong soil erosion affects profoundly soil porosity of slope lands. On slopes the same in parent material but different in erosion intensity, soil pore properties in soil profile vary sharply. This study was oriented to explore spatial distribution pattern of macro-pore properties in soil profile relative to landform positions and soil erosion intensity, a slope of weathered granite under erosion in Shengzhou, Zhejiang Province was taken as the study area. [Method]This study in oriented to characterize macro-pore in soil profiles at different landform positions on the slope, with the help of the Shengzhou Soil and Water Conservation Monitoring Station. Along the slope where the station sits, three typical sites, different in erosion intensity, were selected separately, at the top, middle and bottom. A soil profile or soil column, 70 cm in length, was sampled at each site using PVC pipes with known inner diameter. The columns were then CT- scanned layer by layer with high intensity and their CT images were interpreted with the ArcGIS10.1 image processing technology for analysis of macro-pore distribution and its influencing factors. The pore characteristics indices studied include macro-porosity proportion of macro-porosity to total porosity, anomaly of macro-porosity, circularity of macro-pores, proportion of different classes of macro-pores of equivalent diameter in number, and ratio of macro-pores to total pores.[Result]The following conclusions were drawn from the analysis and calculation:(1)Macro-pores dominated all the three soil profiles, and pores between 1～ 3 mm in diameter were the highest in proportion and pores e between 5～7 mm were the lowest. In terms of number of macro-pores, the three typical soil profiles exhibited a decreasing order of the one at the middle > the one at the bottom > the one on the top; in the soil profiles on the top and at the middle of the slope, the proportion of macro-pores number is comparatively small.(2)The difference between macro-porosity and total porosity was very small in all the three soil profiles and decreased with soil depth. The soil layer with macro-porosity higher than the average was distributed mainly in the upper part of the profiles between 0 cm and 30 cm. The difference between soil layers was not obvious and never exceeded 10%, but the deep in the soil profile, the greater the difference. (3)Circularity of macro-pores was a factor affecting the relationship between macro-porosity and total porosity, while the higher the content of clay and silt, the higher the circularity. (4) The proportion of coarse sand was the highest in all the three profiles, amounting to 50% or more,while the proportion of clay the lowest, being no more than 12%. Correlation of macro- porosity with soil particle size was analyzed with SPSS 20.0, revealing that soil macro-porosity was significantly and positively related to content of coarse sand, but negatively to content of clay and silt. The finer the soil particles, the greater the total porosity and the smaller the proportion of macro-pores.[Conclusion]In a word, severe soil erosion alters the characteristics of soil structure, being porous in the upper and layer and compact in the lower layer. Affected by erosion,the soil profiles are dominated with macro-pores, poor in pore structure. The distribution of macro-pores in the soil profiles is obviously affected by the intensity of erosion. The more serious the erosion, the higher the proportion of macro-pores and the more serious the phenomenon of soil water and nutrient loss. All the findings in this study provide a train of thought for evaluation of soil evolution under erosion and contents of the research on soil evolution.%为了揭示侵蚀性风化花岗岩坡地不同部位土壤剖面大孔隙特性的空间分布,在浙江嵊州市水土保持监测站,同一坡面不同侵蚀强度的坡顶、坡中、坡底选取3个土壤剖面,进行了原状土柱(70cm)样品采集,用CT分层扫描与ArcGIS10.1图像解译技术,获得了系列数据,并计算了分析指标,研究了3个剖面大孔隙的分布规律和影响因素.结果表明:(1)3个土壤剖面均以大孔隙为主, 1～3 mm孔径占比最大,5～7 mm占比最小.大孔隙个数的排序:坡中>坡底>坡顶.(2)大孔隙度与总孔隙度的差值随深度递减.大孔隙度大于均值的层位分布在0～30 cm之间.(3)成圆率影响大孔隙度与总孔隙度的关系.土壤黏粒和粉粒含量越多,成圆率越大.大孔隙度与土壤粗砂粒呈显著正相关,与黏粒和粉粒为显著负相关.(4)土壤侵蚀强度越大,大孔隙占比越大,孔隙结构性越差,漏水漏肥越严重.
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