北方石质山区表层土壤有机碳密度特征分析--以密云县为例

Analysis of Soil Organic Carbon Density in the Lithoid Mountainous Area in North China:A Case Study in Miyun County

基于抽样调查的方法,以北方石质山区典型区域北京密云县为研究区,采集了87个基本抽样单元中的222个样点的表层0～20cm的土壤,通过实验分析与计算得到每个土壤样点的土壤有机碳密度。数据统计结果表明:①研究区有机碳含量变化范围为(0.30～61.00)g/kg,平均有机碳含量为15.7g/kg,变异系数为0.70,属中等强度变异;②土壤有机碳密度介于(0.08～11.01)kg/m2之间,平均值为3.27kg/m2,中值为2.84kg/m2,变异系数为0.59,属中等强度变异;③空间插值结果表明,土壤有机碳密度空间上分布具有一定规律性,该分布特征与土地利用及地形空间分布特征较为一致,有机碳密度分布较高的地区主要分布在密云县北部,及东北部等海拔较高的地区;中等海拔地区,人类活动相对频繁,部分地区植被遭到破坏,水土流失相对严重,该区域有机碳密度明显低于高海拔山区;南部平原区及密云水库周边地区是农、工业生产集中分布地带,该区域有机碳密度最低。

Soil organic carbon pool is the important parts of the whole soil organic carbon pool. Study on the topsoil （0-20cm） organic carbon and organic carbon density play important role in the research of the soil organic carbon. Based on the spot check method, we select Miyun County which is in the lithoid mountainous areas in North China, as the study area to analysis the characteristics of soil organic carbon and soil organic carbon density. 222 soil sampling points in the 87 base sampling areas were selected to calculate the soil organic carbon and soil organic carbon density. The analysis result indicates that the soil organic carbon content is between 0.30- 61.00 g/kg with the mean value of 15.7 g/kg, and the median value of 12.70 g/kg. The variation coefficient is 0.70 and belongs to median variation. The soil organic carbon density is between （0.08-11.01）kg/m^2, with mean value of 3.27 kg/m^2 and median value of 2.84 kg/m^2. Its variation coefficient is 0.59 and belongs to median variation. To analyze the spatial distribution of soil organic carbon density, we calculate its mean value of each soil sample and regard it as the soil organic carbon density of center point in the base sample area （M-Sample）. The parameters of the Kriging exponential model was used to produce the spatial distribution map of soil organic carbon density of the study area. For the spatial interpolation, a cell size of 200m × 200m was chosen to divide the study area into a grid system containing 352 rows and 361 columns. In the study, the nugget-to-sill ratio showed a moderate spatial dependence on soil organic carbon density （the ratio is 0.55）. Comparison of spatial distribution map of soil organic carbon density, land use map and elevation map of the study area show us that the spatial distribution of soil organic carbon density is generally consistent with the distribution of land use type and topography. The soil organic carbon density is higher in the northwest and places with better vegetation coverage, higher elevation, fewer human activities, minor soil erosion. The soil organic carbon density is remarkably lower in the middle elevation area, where human activities are more frequent, and soil erosion is worse. The soil organic carbon density is lowest in the plain which is the location of the human habitation and towns.