湖南典型水耕人为土铁的形态及剖面分异特征

针对不同母质发育水耕人为土（水稻土）中铁的形态及其剖面分异特征开展深入研究，对于正确认识稻田关键元素的分布与行为具有重要意义。本研究以湖南省花岗岩风化物（GR）、板页岩风化物（PS）、第四纪红色黏土（QRC）、石灰岩风化物（LS）、紫色砂页岩风化物（PSS）和近代河湖（冲）沉积物（FLD）共6种母质发育的水耕人为土为研究对象，通过30个典型剖面系统分析了剖面（0~100 cm）及水耕人为土不同土类间铁的形态及其分异特征，探讨土壤剖面铁的形态转变、剖面迁移转化规律。结果表明，湖南省6种典型母质发育的水耕人为土在中国土壤系统分类中的位置已经探明，检索出简育水耕人为土（HSA）、铁聚水耕人为土（FSA）和潜育水耕人为土（GSA）3个土类，暂未发现铁渗水耕人为土。水耕人为土剖面全铁（Fet）含量均值为44.66 g/kg，不同形态铁的构成表现为：晶质铁（Fec）>硅酸盐铁（Fesi）>活性铁（Feo）>络合铁（Fep）。铁的形态在剖面分布呈现出Fesi在剖面变化不大、Fec在剖面呈现先升后降、Feo和Fep在剖面呈现先降后升共三种趋势。PS、QRC和LS的Fec、FLD的Feo、GR的Fep含量均值分别高于其他母质；GR、PS和QRC发育的水耕人为土淀积系数高于LS、PSS和FLD。FSA的Fec含量均值和淀积系数、GSA的Fep含量均值分别显著高于其他土类。研究表明，湖南6种母质发育的典型水耕人为土中铁的不同形态发生转化并在剖面、母质、土类间体现出显著分异。铁的形态及淀积系数反映了水耕人为土的发育程度及成土环境，对于水耕人为土的发生学特性与系统分类具有指示作用。

Characteristics of iron fractions and their differentiation in profile of typical stagnic anthrosols in Hunan Province

The characteristics of iron fractions and their differentiation in stagnic anthrosols (paddy soil) are important parameters for understanding the distribution and behavior of key elements in rice fields. This paper analyzed the iron fractions and their differentiation characteristics along 30 typical profiles (0~100 cm) at the group category level of stagnic anthrosols derived from the granite (GR), plate and shale (PS), Quaternary red clay (QRC), limestone (LS), purple sandy shale (PSS), and fluvial-lacustrine deposit (FLD) in Hunan Province. Based on classified the stagnic anthrosols according to the standards of Chinese Soil Taxonomy, Result showed to retrieve three soil groups of the hapli-stagnic anthrosols (HSA), Fe-accumulation-stagnic anthrosols (FSA), and gleyi-stagnic anthrosols (GSA), but the group of Fe-leachi-stagnic anthrosols was not observed. The mean content of total iron (Fet) in soil profile of stagnic anthrosols in Hunan Province is 44.66 g/kg. The mean content of iron with different fractions are as follows: crystalline iron (Fec) > silicate iron (Fesi) > active iron (Feo) > organic-bounded iron (Fep). Moreover, Fec shows an initial increase followed by a subsequent decline in the profiles, but Feo and Fep indicate an initial decline followed by an upward trend. However, there is no obvious change for Fesi. The mean content of Fec in soil derived from the PS, QRC and LS, the mean content of Feo in FLD, and the mean content of Fep in soil derived from the GR were higher than those from other parent materials, respectively. The illuvial coefficients of soils derived from the GR, PS, and QRC were higher than soils derived from the LS, PSS, and FLD. The mean content of Fec and illuvial coefficient of FSA, and the mean content of Fep in GSA were higher than those of other soil groups, respectively. This research indicated that iron fractions in stagnic anthrosols developed from 6 parent materials in Hunan Province are obviously different, and exhibit significant differentiation between profiles, parent materials, and soil groups. The characteristics of iron fractions and profile differentiation could reflect the soil development levels and soil-forming environments, and have indicative function for the genetic characteristics and Chinese Soil Taxonomy of stagnic anthrosols.