喀斯特地区土壤有机质的稳定碳同位素地球化学特征

以喀斯特地区二种主要的土壤类型石灰土和黄壤为例,对三种植被类型下土壤及土壤不同粒径组分中有机质的稳定碳同位素组成(δ13C值)进行了分析,结果显示:石灰土剖面中土壤有机碳含量均大于1.0%,最大值为表层土的7.1%,而三个黄壤剖面中土壤有机碳含量在0.3%～4.6%之间;石灰土剖面中土壤有机质δ13C值的变化范围仅为-24.1‰～-23.0‰,土壤不同粒径组分中有机质的δ13C值变幅也较小;而黄壤剖面中土壤有机质δ13C值的变化范围较大,在-24.5‰～-21.1‰之间,土壤不同粒径组分中有机质的δ13C值变幅也较大。对比研究表明,不同土壤类型中有机质的深度分布特征具有显著差异,土壤有机质的稳定碳同位素地球化学具有明显的区域性特征。

GEOCHEMICAL CHARACTERISTICS OF STABLE CARBON ISOTOPES IN SOIL ORGANIC MATTER FROM KARST AREAS

Taking limestone soil and yellow soil,the two major soil types in karst areas,for examples,we analyzed the δ13C values of soil organic matter in bulk soils and particle-size separates of four soil profiles under three vegetable forms.The results revealed that in the limestone soil profile,soil organic carbon contents are all above 1.0%,and the highest value is 7.1% in the surface soil,however,they are between 0.3%～4.6% in the three yellow soil profiles.From the surface to the bottom of the soil profiles,the δ13C values of soil organic carbon for the limestone soil profile vary only between –24.1‰～–23.0‰,–24.5‰～–21.1‰ for the yellow soil profiles.The variation range of δ13C values of soil organic carbon associated with particle-size separates is small for limestone soil but is considerably large for yellow soil.The contrast research indicated that there is a significant difference in variation between the contents and the δ13C values of soil organic matter with depth in these two soil types.The stable carbon isotope geochemistry of soil organic matter shows distinct regional characteristics in karst areas.