不同退耕年限下菜子湖湿地土壤铁形态变化

Characteristics of soil iron forms in wetlands with various restoration ages around the Caizi Lake,Anhui Province

选取菜子湖区不同退耕年限（3、5、7、9、11、21 a）湿地为研究对象,以仍耕作油菜地和原始湿地为参照,分别采用王水消解法和Tessier连续提取法,分析了退耕还湖后湿地土壤全铁和铁的赋存形态特征,探讨退耕还湖后湿地土壤铁组分特征变化规律.结果表明：研究区土壤铁各形态含量大小顺序为：残渣态（RES-Fe：17.09-30.84 g·kg-1）〉铁锰氧化态（RED-Fe：3.66-4.48 g·kg-1）〉有机结合态（OM-Fe：0.87-3.09g·kg-1）〉碳酸盐结合态（CARB-Fe：0.01-0.37 g·kg-1）〉可交换态（EXC-Fe：0.01-0.15 g·kg-1）.占全铁均小于1.5%的EXC-Fe和CARB-Fe均在退耕3 a和5 a期间含量快速升高,而后降低再升高,最低值出现在退耕11 a;RED-Fe在退耕3-9 a比较稳定,随后缓慢增加;而OM-Fe随退耕年限增加整体上呈增加趋势;占土壤铁形态总量73.91%-85.42%的RES-Fe在退耕3a时含量下降,在3-9 a间呈现逐渐增加的趋势,9-21 a又逐渐下降;研究区全铁（Tot-Fe）平均含量在18.50-38.41 g·kg-1之间,变化趋势与RES-Fe基本一致.讨论结果表明退耕还湖后水文条件和植被状况的改变导致了土壤环境发生变化,从而不仅影响退耕后湿地土壤全铁含量变化,也影响土壤铁形态组分特征,进而影响土壤铁的有效性.

The aqua regia digestion method and Tessier sequential extraction procedure were conducted to investigate soil total iron content and characteristics of iron forms in wetlands with various ages（ 3,5,7,9,11 and 21 years） of returning farmland to lake（ RFL）,rape field,and native wetland around the Caizi lake,Anhui province. The results showed that the contents of various soil iron forms were in the order： RES-Fe（ 17.09 - 30.84g·kg-1） RED-Fe（ 3.66-4.48 g·kg-1） OM-Fe（ 0.87-3.09 g·kg-1） CARB-Fe（ 0.01-0.37 g·kg-1） EXC-Fe（ 0.01-0.15 g·kg-1）. EXC-Fe and CARB-Fe,accounting for less than 1.5% of soil total iron,increased rapidly at the first 3a and 5 a of RFL,then began to decline after 7 a and showed lowest contents at 11 a of RFL. The RED-Fe contents tended to be stable within the restoration period of 3 - 9 a,and then increased gradually after9 a of RFL. The contents of OM-Fe increased progressively with the increasing restoration age of RFL. Soil RES-Fe contents,accounting for 73. 91% -85.42% of total iron,increased within the restoration period of 3 - 9 a,then declined after 9 a. The contents of Tot-Fe were 18.50 - 38.41 g·kg-1,showing the same change tendency as the RES-Fe. Changes in soil total iron contents,iron form composition,and iron availability might be attributed to modification in soil physical and chemical properties induced by changes of hydrological condition and vegetation recovery status after RFL.