典型岩溶流域不同土地利用类型土壤腐植酸与钙的关系

为了阐明岩溶地区不同土地利用类型中土壤腐植酸的分布特征及其与钙的关系，以滇东南典型岩溶流域普者黑流域为研究对象，分析流域内裸地、林地、旱地、水田和湿地5种土地利用类型中土壤表层（0~10 cm）、亚表层（10~20 cm）的水溶性有机质（WSOM）、胡敏酸（HA）、富里酸（FA）的分布情况，并进一步探究土壤中腐植酸的结构特征及其含量与钙的关系。结果表明：研究区5种土地利用类型土壤中WSOM、HA和FA含量的空间变幅均较大（P<0.05），且表层 > 亚表层（P<0.05），腐植酸含量（WSOM、HA、FA三者含量之和）的大小依次为旱地（13 289.97 mg·kg^-1） > 湿地（10 007.02 mg·kg^-1） > 林地（9 136.76 mg·kg^-1） > 水田（8 708.724 mg·kg^-1） > 裸地（3 395.13 mg·kg^-1）； 5种土地利用类型土壤PQ值（HA在腐植酸中的比例）以及HA/FA（可以在一定程度上反映土壤有机质的稳定性）的空间变幅较大且变化规律相似，大小排序均为水田 > 湿地 > 林地 > 旱地 > 裸地（P<0.05）；红外图谱分析表明5种土地利用类型土壤的腐植酸具有类似的结构组成和官能团信息，除含有一定量的芳香结构外，还含有大量的羟基、氨基、酚羟基、醇羟基以及脂肪链结构；冗余分析表明土壤全钙及各形态钙在很大程度上影响腐植酸的种类及含量。研究表明，普者黑岩溶流域内5种土地利用类型土壤腐植酸含量空间变幅较大，结构相似且特征明显，与土壤钙的关系密切，同时普者黑流域内5种土地利用类型土壤的腐殖化程度较高，腐植酸品质较好。

Relationship between humic acids and calcium fractions in soils under contrasting land-use types in a typical karst basin

To clarify the distribution characteristics of soil humic acid and its relationship with calcium under different land-use types in a karst area, a study was performed in the Puzhehei basin, a typical karst basin in southeast Yunnan. The distributions of water-soluble organic matter(WSOM), humic acid(HA), and fulvic acid(FA) in soil surface(0~10 cm) and sub-surface(10~20 cm) under five landuse types were analyzed, and the structural characteristics of HA in soil and the relationship between its content and calcium was further explored. The results showed that the spatial variations of w(WSOM), w(HA) and w(FA) under the five land-use types were significant (P<0.05), and the spatial variation was greater at the surface than the subsurface(P<0.05). The content of the humic acids (sum of WSOM, HA, FA) was ranked as dryland(13 289.97 mg·kg^-1) > wetland(10 007.02 mg·kg^-1) > forest(9 136.76 mg·kg^-1) > paddy field(8 708.72 mg·kg^-1) > bare land(3 395.13 mg·kg^-1). The spatial variation of soil PQ values(the proportion of HA in humic acids) and HA/FA(which could reflect the stability of soil organic matter to some extent) under the five land-use types was large and the variation was similar(P<0.05). The PQ and HA/FA values were ranked as paddy field > wetland > forest > dryland > bare land. The infrared spectra of humic acids under the five land-use types showed similar structural composition and functional groups, and they contained large amounts of hydroxyl, amino, phenolic hydroxyl, alcohol hydroxyl, and fatty chain structures in addition to a certain amount of aromatic structures. Redundancy analysis showed that soil total calcium and various forms of calcium greatly affected humic acids species and content. The results showed that soil humic acids content under the five land-use types in the Puzhehei karst basin varied greatly in space, had similar structure and obvious characteristics, and was closely related to soil calcium. At the same time, the soil under the five land-use types in the Puzhehei River basin had good humic acids quality and high degree of humification.