侵蚀红壤腐殖酸组分特点及其对水稳性团聚体的影响

CHARACTERISTICS OF HUMUS FRACTION IN EROSION ULTISOLS AND THEIR EFFECTS ON WATER-STABLE AGGREGATES

在华中地区采集不同侵蚀程度（轻度、中度、严重）的红壤，利用干湿筛法获得不同粒径的水稳性团聚体（〉0.25 mm）。通过测定不同粒径水稳性团聚体（〉0.25 mm）的腐殖酸组分（胡敏酸和富里酸）碳量，以及向不同侵蚀程度的各粒径团聚体（〉0.25 mm）中添加不同浓度（0.06、0.6 g L^-1）的胡敏酸，分析侵蚀红壤腐殖酸组分特点及其对水稳性团聚体的影响。结果表明：随着侵蚀程度的增加，供试红壤和水稳性团聚体（〉0.25 mm）的腐殖酸组分含量减少；轻度和中度侵蚀红壤中，大粒径（〉4和2～4 mm）水稳性团聚体的胡敏酸碳量较小粒径（1～2、0.5～1和0.25～0.5 mm）的高；同种侵蚀程度下，除严重侵蚀红壤中2～4 mm团聚体的富里酸碳量与1～2 mm团聚体中的有显著差异外，不同粒径团聚体中富里酸碳量差别不大。3种侵蚀程度红壤的胡富比总体上小于1，其中中度侵蚀红壤和各粒径水稳性团聚体的胡富比均大于其他两种侵蚀程度的。腐殖酸组分与水稳性团聚体（〉0.25 mm）含量呈极显著正相关，与胡敏酸碳量的相关系数最大（r=0.85^＊＊ ，n=19）。添加不同浓度（0.06和0.6 g L^-1）胡敏酸后，3种侵蚀程度红壤各粒径水稳性团聚体（〉0.25 mm）的含量均增加，且小粒径团聚体（1～2、0.5～1和0.25～0.5 mm ）的增加量要高于大团聚体（2～4、〉4 mm）的。

Samples of Ultisols different in erosion degree （slight, medium and severe） were collected in Central China and treated with the drying-wetting sieving method for different fractions of water-stable aggregates, 〉0.25 mm in particle-size. Carbon contents in different components of fumic acid （humic and fulvic acids） in these aggregates were analyzed for characteristics of humic acid in composition, and effects of amendment of different concentrations （0.06 and 0.6g L^-1） of humic acid in the fractions of aggregates from soils different in erosion degree explored. Results show that with erosion aggravating, the content of humic acids in Ultisols and water stable aggregates decreased. In Ultisols slight and medium in erosion, HA carbon content is higher in water-stable aggregates, 〉4 and 2-4 mm in particle size than in water-stable aggregates, 1-2, 0.5-1 and 0.25-0.5 mm in particle size. In Ultisols the same in erosion degree, fractions of aggregates did not differ much in FA carbon content, except for soils severe in erosion degree, where the fraction （2-4 mm） differed sharply from the fraction （1-2 mm） in FA carbon content. HA/FA ratios in all the Ultisols different in erosion degree were generally less than 1 and the Ultisols medium in erosion degree were higher than those slight or severe in erosion degree in HA/FA ratio in all fractions. Humic acid composition was significantly positively related to content of water-stable aggregates （〉0.25 mm）, and the correlation coefficients of HA carbon content were the highest （r=0.85^＊＊ ,n=19）. After amendment of humic acid at 0.06 or 0.6 g L^-1, the contents of all fractions of aggregates increased in all the soils different in erosion degree, and the extent of the increase was higher in 1-2, 0.5-1 and 0.25-0.5 mm fractions of aggregates than in 2-4 and 〉4 mm fractions of aggregates.