紫色土区植物篱篱前淤积带土壤团聚体稳定性特征研究

Study on Stability of Soil Aggregates in the Sedimentation Zone in Front of Hedgerows in Purple Soil Area

为探讨紫色土区植物篱篱前淤积带土壤团聚体的稳定性,试验以该淤积带土壤为研究对象,设置了10°对照小区(T1)、10°新银合欢植物篱小区(T2)、10°香根草植物篱小区(T3)、15°对照小区(T4)、15°香根草植物篱小区(T5)等5个处理,采用萨维诺夫法测定了风干团聚体和水稳性团聚体的组成状况,以保存机率、稳定性指数、PAD(结构体破坏率)、MWD(平均重量直径)、GMD(几何平均直径)、MWSSA(平均重量比表面积)、CS(偏度系数)和CE(峰凸系数)等为评价指标,分析了不同坡度、不同植物篱种类下篱前淤积带土壤团聚体稳定性特征。结果表明:(1)各个小区篱前淤积带的水稳性团聚体数量表现为T2和T3小区明显大于T1,T5小区略微大于T4小区但不明显,大坡度下植物篱对紫色土起到保土减沙作用需要一个前期过程。(2)同一坡位情况下,各个小区篱前淤积带土壤团聚体稳定性指数表现为T3>T2>T1、T5>T4,而PAD则表现为T1>T2>T3、T4>T5,较之对照小区,植物篱表现出对土壤团聚体抗侵蚀性的强化效应。(3)同一坡位情况下,风干团聚体、水稳性团聚体的MWD、GMD和CS均表现为T3>T2>T1、T5>T4,而MWSSA则相反,香根草植物篱较新银合欢植物篱更有利于增强团聚体的结构稳定性。(4)PAD能很好地描述干、湿筛处理前后团聚体的稳定性变化,风干团聚体的CS可作为评价团聚体抗机械稳定性的最佳指标,水稳性团聚体的MWD和GMD可更好地表达团聚体的水稳定性。

In order to explore soil aggregates stability of sedimentation zone in front of hedgerows in purple soil area,taking purple soil under these zones as the research object,this article set 10°blank control（T1）,10°Leucaena leucocephala hedgerows（T2）,10°Vetiveria zizanioides hedgerows（T3）,15°blank control（T4）and 15°Vetiveria zizanioides hedgerows（T5）.The composition of air-dried aggregates and waterstable aggregates was measured by the Savinov method.Using a series of evaluation indicators（save probability,stability index,percentage of aggregate destruction,mean weight diameter,geometric mean diameter,mean weight soil specific area,bias coefficient,peak convex coefficient）,this article analyzed soil aggregates stability characteristics of sedimentation zone in front of hedgerows on different slopes and different hedgerow types.The results indicated that：（1）The number of water-stable aggregates in T2 and T3 was significantly larger than that of T1,and the T5 was slightly larger than that of T4.There was a pre-process that hedgerows could produce effect in soil conservation of steep slopes.（2）In the same slope position,the stability index of soil aggregates in sedimentation zone in front of hedgerows was：T3〉T2〉T1,T5〉T4,while PADshowed T1〉T2〉T3,T4〉T5.Compared with blank control,hedgerows showed that it can enhance effect on anti-erodibility of soil aggregates.（3）At the same slope position,the MWD,GMD and CS of air-dried aggregates and water-stable aggregates showed T3T2T1,T5T4,whereas the MWSSA showed opposite trend.Vetiveria zizanioides hedgerows were more beneficial to enhance the stability of aggregates than that of Leucaena leucocephala hedgerows.（4）PAD could well describe the stability of aggregates before and after wet and sieve treatment.The CSof air-dried aggregates could be used as the best index to evaluate the mechanical stability of aggregates.The MWD and GMD of water-stable aggregates could better express the water stability of the aggregates.