亚热带典型景观单元土壤有机碳含量和密度特征

以我国亚热带四类典型景观单元表层土壤为对象,对比分析了土壤有机碳（SOC）含量和密度特征.结果表明,四类景观单元SOC含量加权平均值差异明显,以平原湖区加权平均值最高（25.10 g·kg^-1）,其次为喀斯特低山（20.84 g·kg^-1）和红壤低山（17.75 g·kg^-1）,红壤丘陵平均值最低（12.07 g·kg^-1）.四类景观单元SOC含量变异系数在24.06%～43.76%之间,均属于中等程度变异.平原湖区景观SOC含量主要分布区高于20 g·kg^-1,其它三类景观单元主要分布区则相反.四类景观单元SOC密度加权平均值大小顺序与SOC含量高低极为一致,其顺序为平原湖区（6.12 kg·m^-2）> 喀斯特低山（4.30 kg·m^-2）> 红壤低山（4.25 kg·m^-2）> 红壤丘陵（3.04 kg·m^-2）.研究结果揭示成土母质、耕作强度、地形差异和土地利用方式比例是SOC含量景观变异的主要原因,亚热带地区典型景观单元土壤可能是我国重要的碳库.

Content and Density Characteristics of Soil Organic Carbon in Typical Landscapes of Subtropical Region

The contrasts of the content and density characteristics of surface soil organic carbon among four typical landscapes of subtropical region in China were investigated. The results show that the area-weighted mean content of SOC varies widely with landscapes and the highest mean content is present in the lacustrine plain landscape (25.10 g·kg~(-1)) , followed by the karst landscape (20.84 g·kg~(-1)) and mountainous landscape (17.75 g·kg~(-1)), whereas the lowest occurs in the hilly red soil landscape (12.07 g·kg~(-1)). The coefficient of variation of SOC content ranges from 24.06% to 43.76% , being moderate variation. The main distribution ranges of SOC content are higher than 20 g· kg~(-1) in the lacustrine plain landscape and lower than 20 g·kg~(-1) in the other three landscapes. The sequence of SOC density in the four landscapes is highly consistent with the sequence of SOC content, and the sequence is as follows: lacustrine plain landscape (6.12 kg·m~(-2)) > karst landscape (4.30 kg· m~(-2)) > mountainous landscape (4.25 kg·m~(-2) ) > hilly red soil landscape (3.04 kg·m~(-2)). The results reveal that the difference of soil parent material, cultivation strength, topography and proportion of land use may be the main reasons caused the variation of SOC content among the four landscapes. Surface soils in typical landscapes of subtropical region are important carbon pool in China.