Rheological characteristics of soils, including their deformation and flow behaviors when subjected to external stress, can provide important information on microstructural stability. In this study we used rheological measurements to examine the soil aggregate microstructure and stability of four different soil orders – Alfisol, Mollisol, Inceptisol, and Entisol – along a forested catena in Mazandaran Province, northern Iran. Amplitude sweep tests were used to quantify the initial values of the storage and loss moduli, deformation limit (when the material begins to transition from reversible to irreversible deformation), deformation at flow point (when the material becomes viscous), and integral z (which summarizes the overall visco-elasticity of the material). The deformation limit was significantly higher in subsoil layers than topsoil layers, and was also higher in the Mollisol than the other pedons. The flow point and integral z values, which relate to the structural stiffness of soil matrices, were largest in the Btg horizons of the Alfisol and Mollisol, implying that these soils had more rigid microstructures. In contrast, the Entisol Ckg horizon, which had high sand content and little soil development, had the lowest values for all properties, thus indicating a lack of micro-aggregate stability. Regression analyses revealed that integral z was influenced by soil physicochemical properties, and was higher in soils whose clay fraction was dominated by expansive clay minerals and pedogenic iron and aluminum sesquioxides. Altogether, the rheological parameters indicated that older, more developed soils had greater microstructural stability than their less developed counterparts. As a result, rheological measurements may be useful for identifying the major factors that affect soil aggregation, and can indicate the relative amount of soil development along gradients such as the studied forest catena.

土壤的流变特性，包括在受到外力作用下的变形和流动行为，可以提供有关微结构稳定性的重要信息。在这项研究中，我们使用流变学测量方法，研究了伊朗北部Mazandaran省沿森林的林地中四个不同土壤阶次-Alfisol，Mollisol，Inceptisol和Entisol的土壤团聚体微观结构和稳定性。振幅扫描测试用于量化存储和损耗模量的初始值，变形极限（当材料开始从可逆变形转变为不可逆变形时），流动点的变形（当材料变粘时）以及积分z（总结了材料的整体粘弹性）。在下层土壤中，变形极限明显高于表层土壤，并且在Mollisol中，变形极限也比其他土壤岩层更高。与土壤基质的结构刚度有关的流点和积分z值在Alfisol和Mollisol的Btg层中最大，表明这些土壤具有更坚硬的微观结构。相反，Entisol Ckg地层含沙量高，土壤发育少，其所有特性的数值最低，因此表明缺乏微骨料的稳定性。回归分析表明，积分z受到土壤理化性质的影响，在粘土成分以膨胀粘土矿物和成岩铁和铝倍半氧化物为主的土壤中含量较高。总的来说，流变参数表明，较老的，较发达的土壤比较不发达的土壤具有更高的微观结构稳定性。结果，流变学测量对于确定影响土壤聚集的主要因素可能有用，并且可以指示沿梯度的土壤发育的相对量，例如研究的森林链。