侵蚀红壤中结合态腐殖质及其与水稳性团聚体的关系

Combined Humus of Eroded Ultisols and Its Relationship with Water-stable Aggregates

以亚热带地区3种侵蚀程度（依据其植被、坡度以及土层厚度不同分为轻度、中度和严重侵蚀）的红壤为供试材料，利用湿筛法获得粒径〉4、2～4、1～2、0．5～1、0．25～0．5mm的水稳性团聚体，分析侵蚀红壤和团聚体中3种结合态（紧结态、松结态和稳结态）腐殖质含碳量的分布特征，及其对〉0．25mm团聚体稳定性的影响。结果表明：随着红壤侵蚀程度的增强，3种结合态腐殖质的含碳量均逐渐减小。在轻度侵蚀的红壤中，随着团聚体粒径的增大，其紧结态和松结态腐殖质的含碳量逐渐升高，稳结态腐殖质的含碳量逐渐降低；但是在中度和严重侵蚀红壤中，不同粒径团聚体的3种结合态腐殖质的含碳量基本相同。侵蚀红壤的紧结态、松结态腐殖质的含碳量与其〉0．25mm水稳性团聚体的含量均呈极显著正相关（r分别为0．88，0．74），说明土壤中腐殖质与矿物质的结合方式和松紧程度不一样，其对侵蚀红壤的结构具有不同的影响。

The distribution of combined humus in soil aggregates of particle size ranging from 〉4, 2-4, 1-2, 0.5-1 and 0.25-0.5 mm in three eroded （according to its vegetation, slope and soil thickness divided into slightly, moderately and severely erosion） Ultisols in subtropical regions of China and its relationship with the average percentage of 〉0.25 mm water-stable aggregates （WSA） were investigated by using wet-sieving method. Results showed that the carbon contents in three kinds of combined humus （tightly, loosely and steadily） decreased with erosion aggravating. In the slightly eroded soil, the carbon content of tightly and loosely combined humus in aggregates increased with increasing particle size, while the carbon content of steady combined humus decreased. In moderately and severely eroded soil, the carbon contents in the three kinds of combined humus were close in different size aggregates. The carbon content of three kinds of combined humus showed highly significant positive correlation with the percentage of 〉 0.25 mm water-stable aggregates in soil of different erosion degrees （r = 0.88 and 0.74）. This showed that the different blinding modes and tightness of minerals and humus had different effects on eroded soil structures.