Studies on Humus Complexes and Charge Characteristics of Volcanic Ash Soils in Tropics and Subtropics

本文研究了来自七个国家的100个不同气候条件下的土壤样品，它们分为Udands、Cryands、Perands、Usands、Xerands和Vitrands，以及其他目的Andic或Vitrandic亚类。（3）Al-和Fe-腐殖质复合体的成土意义，腐殖质积累的时间关系以及T-C与Alpyr或（Al + 1/2Fe）pyr研究表明，腐殖土中腐殖质的积累和稳定化与Al-和Fe-腐殖质复合物的形成同时进行，而不考虑踏板所经历的不同气候条件。T-C与Alox-pyr或（Al + 1/2Fe）ox-pyr之间缺乏相关性进一步支持了Alpyr和Fepyr在Andisols腐殖质积累中的意义。33个Andisol土壤样品的Alpyr/Cpyr和（Al + Fe）pyr/Cpyr原子比分别为0.14和0.17，表明聚合态和单体态的羟基Al和Fe离子都与腐殖质紧密结合，形成Al-和Fe-腐殖质复合体。腐殖酸的积累似乎延缓了水铝英石和伊毛戈兰石的形成，这表现在（Al +1/2Fe）pyr/（Al + 1/2Fe）ox比值与T-C含量的显著正相关以及腐殖物质对它们的影响。这种阻滞作用对非Andepts中的腐殖质比Andepts中的腐殖质更大。因此，目前的结果表明，Al-和Fe-腐殖质复合物值得密切关注，在我们的努力，以了解成壤作用和独特的性质Andisols，这些复合物是非常重要的关系，在andic土壤性质的allic和/或melanic大集团在Udands和Cryands，和其他阶的Andic子群。

Soil samples of 100 pedons, classified as Udands, Cryands, Perands, Ustands, Xerands and Vitrands, and Andic or Vitrandic subgroups in other orders, from seven countries under varying climatic conditions were studied with particular reference to: (1) humus accumulation and the formation of Al- and Fe-humus complexes; (2) the nature of Al- and Fe- humus complexes; and (3) the pedogenic significance of Al- and Fe-humus complexes.The humus accumulation-time relationships and the significant positive correlations between T-C and Alpyr or (Al + 1/2Fe)pyr suggested that the accumulation and stabilization of humus in Andisols proceeded simultaneously with the formation of Al- and Fe-humus complexes, irrespective of the differing climatic conditions experienced by the pedons. Implication of Alpyr and Fepyr in humus accumulation in Andisols was further supported by the lack of correlation between T-C and Alox-pyr or (Al + 1/2Fe)ox-pyr. The Alpyr/Cpyr and (Al + Fe)pyr/Cpyr atomic ratios for samples of 33 Andisol pedons were 0.14 and 0.17 respectively, suggesting that both polymerized and monomeric hydroxy Al and Fe ions would be in close association with humus to form Al- and Fe-humus complexes. The accumulation of humus seems to retard the formation of allophane and imogolite, as indicated by the significant positive correlations between the ratio of (Al + 1/2Fe)pyr to (Al + 1/2Fe)ox and the content of T-C, and by the influence of humic substances on their formation. This retardation effect was greater for the humus present in non-Andepts than for that in Andepts.The present results thus indicate that Al- and Fe-humus complexes merit close attention in our efforts to understand the pedogenesis and distinctive properties of Andisols, and that these complexes are very important in relation to andic soil properties in allic and/or melanic great groups in Udands and Cryands, and in Andic subgroups in other orders.