土壤厚度是土壤退化及土地生产力水平评价的一个重要指标。本研究应用插钎法,调查了北京市密云县山区50个基本抽样单元的坡面土壤厚度。对样点数据进行了统计分析,结果表明:平均土壤厚度为15cm。小于10cm的土壤占37%,小于20cm的土壤占76%,小于30cm的占90%。空间上土壤较厚的区域主要集中在西北和东北部植被覆盖较好的地区。对影响土壤厚度的因子进行分析发现:土壤厚度与海拔无明显相关性,而坡向对土壤厚度的影响较为明显,阴坡土壤厚度明显大于阳坡。土壤厚度与植被覆盖度和坡度明显相关,与植被覆盖度的相关系数为0.84,与坡度的相关系数为-0.40,二者都通过了显著水平为0.01的显著性检验。

Soil depth is an important index in appraising soil degradation and soil productivity. In the lithoidal mountainous area of northern China, the soil horizon is thin, with high rock fragments contents. In the interest of shortcut soil depth survey, the research was carried out with penetration method, that is penetrating a steel drill of 1.2 m long with a diameter of 0.6cm into the soil vertically until the tip reaching the bedrock, and measuring the length of the section which has been penetrated into the soil. Statistics and analysis of the survey data showed that 76% of the soil depth is less than 20cm, 90% of the soil depth is less than 30cm, and the average soil depth is 15cm. The spatial variability of soil depth in two meters distance belongs to median level. The variability coefficient of 93% of the samples is between 0.1 and 1, 7% higher than 1. The spatial distribution map of soil depth indicated that the soil depth is deeper in the northwest comparatively with the vegetation type of woodland and shrubbery, where the cover rate is high, and human function is sparse. Soil erosion intensity is low. The factors affecting soil depth were also analyzed. The results showed that the correlation of soil depth and elevation was not significant. Because all the elevation of sample point selected is below one kilometer and the elevation is not high enough to cause the element change. Soil depth has distinctiveness within different aspects; the soil depth of southern aspect is smaller than that of the northern. Moreover, soil depth was positively and negatively related with vegetative cover and slope gradient, respectively, for soil depth increased with the vegetative cover and decreased with the slope gradient. So the topographic factors (slope, aspect) and the vegetative cover are the major factors dominating the characteristics of soil depth distribution. The research method is simple and shortcut, and the result will provide basic data for mountain land use and project of soil and water conservation.