密云水库上游流域土壤有机碳特征及其影响因素

Characteristics and Influencing Factors of Soil Organic Carbon in Upstream Watershed of Miyun Reservoir in North China

以密云水库上游流域7种典型土地利用类型为研宄对象，分析了不同土地利用类型及不周土层土壤有机碳含量的分布特征及其与气候、地形和土 壤特征等因素的关系。结果表明：①研究区域内天然次生林和草地的土壤有机碳含量最为丰富，其次分别为灌丛和人工林，农田最低：0～40cm土层中，土壤有机碳平均含量由高到低排序为：杨桦林〉草地〉辽东栎林〉灌从〉落叶松林〉油松林〉农田；②除草地外，其他6种土地利用类型土壤有机碳含量均以0-10cm土层最人，随着土层深度的增加呈现降低的趋势，且降幅较大：而草地土壤有机碳含量在0—20cm范围内随剖面的延伸略有增加，20cm以后表现为下降的趋势，各l：层之刚的变化幅度均较小：③各土层土壤有机碳含量均与海拔、土壤含水量、土壤全氮含量呈极显著正相关（P〈0．01），而与年平均温度、年降水量、土壤体积质量和土壤pH值里极显著负相关（p〈0．01），与坡度之间存在很弱的正槲关且未达到显著水平（p〉0．05）；偏相关分析表明，影响土壤有机碳含量的关键因素随土壤深度不同而不同。其中0—10cm上层土壤有机碳含量最主要的影响因素为土壤全氮含量、土壤体积质量和土壤pH值．而10-20cm土层为土壤全氮含量、土壤体积质量和坡度，20～40cm土层则为土壤全氮含量和年降水量：④影响不同士地利用类型土壤有机碳含量的主要因素。草地和农田均为土壤全氮含量和年平均温度．落叶松林为土壤全氮含量和土壤含水量，油松林为土壤体积质量、土壤令氮含量和土壤pH值，杨桦林和辽东栎林均为土壤全氮含量和土壤体积质量，灌丛则为土壤pH值。

Soil organic carbon （SOC） pool constitutes an important portion of the global carbon pool and has significant impacts on land productivity and global climate change. The study on soil organic carbon has been one of the hot issues of the world. However, related research of the filed in the Upstream Watershed of Miyun Reservoir, the largest reservoir in North China, is relatively rare. The distribution characteristics and influencing factors （such as climate, topography and soil characteristics） of soil organic carbon in seven kinds of typical land use types of the Upstream Watershed of Miyun Reservoir were analyzed in the study, and the results showed as follows. 1） In the target domain, soil organic carbon contents in natural secondary forests and grasslands were much higher than those in shrubs and artificial forests, while that in croplands was the lowest. In the whole soil profile （0- 40 cm）, the average soil organic carbon content was in order of natural secondary Populus davidiana Dode-Betula platyphylla Suk. mixed forest 〉 grassland 〉 natural secondary Quercus wutaishanica Blume forest 〉 shrub 〉 artificial Larix principis-rupprechtii Mayr. forest〉artificial Pinus tabulaeformis Carr. forest〉cropland. 2） Soil organic carbon contents in the top soil layer （0 - 10 cm） were the highest and decreased rapidly with the increase depth in the six kinds of land use types except grassland, which showed a slight increase from 0 to 20 cm and a small drop from 20 to 40 cm in depth. 3） Soil organic carbon content in each layer was significantly positively correlated with altitude, soil water content and nitrogen content （p〈0.01）, but remarkably negatively correlated with annual mean temperature, annual precipitation. soil bulk density and pH （p〈0.01）. In addition, soil organic carbon content showed a little positive correlation with slope （p〉0.05）. Further partial correlation analysis indicated that the most principal factors influencing soil organic carbon content varied with soil depth, and they were soil nitrogen content, bulk density and pH in the 0 - 10 cm layer, soil nitrogen content, bulk density and slop in the 10 - 20 cm layer, soil nitrogen content and annual precipitation in the 20 - 40 cm layer, respectively. 4） Furthermore, the most significant factors influencing soil organic carbon content also varied with land use types, and they were soil nitrogen content and annual mean temperature in grassland and cropland, soil nitrogen content and water content in artificial Larix principis-rupprechtii Mayr. forest, soil bulk density, nitrogen content and pH in artificial Pinus tabulaeformis Carr. forest, soil nitrogen content and bulk density in natural secondary Populus davidiana Dode-Betula platyphylla Suk. mixed forest and natural secondary Quercus wutaishanica Blume forest, and only pH in shrub, respectively.