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

本文对7个国家不同气候条件下的100个土壤样品进行了研究，包括：(1)腐殖质的积累和Al-Fe-腐殖质复合体的形成：(2)Al-和Fe-腐殖质复合体的性质，(2)Al-和Fe-腐殖质复合体的性质；腐殖质积累-时间关系和T-C与Alpyr或(Al+1/2Fe)Pyr的显著正相关表明，无论土壤所处的气候条件如何，安第斯土壤腐殖质的积累和稳定与Al和Fe-腐殖质复合体的形成是同步进行的。AlOX-PYR或(Al+1/2Fe)OX-PYR与T-C之间缺乏相关性，进一步支持Alpyr和Fepyr在安第斯土壤腐殖质积累中的意义。33个安迪生土层的Alpyr/Cpyr和(Al+Fe)Pyr/Cpyr原子比分别为0.14和0.17，表明聚合和单体羟基Al和Fe离子均与腐殖质形成Al-和Fe-腐殖质络合物。腐殖质的积累似乎延缓了尿磷石和蒙脱石的形成，(Al+1/2Fe)Pr/(Al+1/2Fe)Ox与T-C含量呈显著正相关，腐殖质对其形成的影响也表明了这一点。这些结果表明，Al-和Fe-腐殖质复合体在理解安第斯土的土壤发生和独特性质方面值得密切关注，而且这些复合体在Udands和Cryands的金属和/或黑色大类群以及其他目的Andic亚类中对Andic土壤性质的影响是非常重要的。

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.