鼎湖山土壤有机质深度分布的剖面演化机制

MECHANISM OF DISTRIBUTION OF SOIL ORGANIC MATTER WITH DEPTH DUE TO EVOLUTION OF SOIL PROFILES AT THE DINGHUSHAN BIOSPHERE RESERVE

根据鼎湖山森林植被带(SL)、灌丛—草甸过渡带土壤剖面(GC)有机质含量,有机质Δ14C、δ13C值,土壤粘粒含量及孢粉分析结果,研究华南亚热带山地土壤有机质深度分布特征的成因机制。结果表明土壤有机质的深度分布特征与土壤剖面的发育过程密切相关,随深度增大,有机质的来源数量不断减少,而成土时间增加,分解作用导致的有机质含量降低幅度增大,有机质含量不断减少。土壤有机质14C表观年龄随深度增加,土壤有机质δ13C值与有机质含量的深度变化具有明显对应关系,这些都是土壤剖面发育过程中有机质不同更新周期组分呈规律性分解的结果。粘粒的深度分布反映土壤剖面淋滤淀积的特点,表明土壤剖面经受了长期成土风化。土壤剖面的上述特征均为剖面发育过程中不断沉积、不断成土的结果,表明土壤剖面成土演化对于有机质深度分布具有显著制约。

Mechanism of distribution of soil organic matter (SOM) with depth was studied based on SOM content, SOM Δ^(14)C, SOM δ^(13)C, clay content and sporopollen composition of two soil profiles at the forest vegetation zone and shrub-meadow zone in the Dinghushan Biosphere Reserve. Results indicated that distribution of SOM with depth was related to the evolution of soil profiles. With the depth SOM sources decreased but SOM loss increased due to SOM decomposition during evolution of the soil profiles and SOM content decreased gradually while SOM ()^(14)C apparent age increased. Obvious correlationship was observed between variation of the SOM δ^(13)C value with the depth and that of the SOM contents with the depth. All these were the result of regular decomposition of SOM in different replacement periods during the development of the soil profiles. Vertical distribution of clay reflected the characteristics of pedological illuviation of the soil profiles, indicating that the soil profiles had undergone a long period of pedogenic weathering. The above characteristics of the soil profiles are the results of continuous deposition and soil formation during evolution of the soil profiles, suggesting a significant restraining effect on distribution of SOM with the depth.