Changes in soil pores and aggregate stability due to freeze-thaw cycles (FTCs) are important causes of increased soil erosion during snowmelt. Soil erosion causes spatial redistribution of soils, enhancing soil heterogeneity and potentially impacting soil responses to FTCs. Nonetheless, there is minimal knowledge of the responses of soils subjected to different degrees of erosion to seasonal FTCs. To reveal the impact of seasonal FTCs, the dynamic variations of pore characteristics and aggregates of soils with four different degrees of erosion (original, degraded, deposited and parent soil) were measured, and the connections between influencing factors and soil properties were analyzed. The results showed that FTCs altered the structure of the soils and weakened their resistance to erosion and that soils with different degrees of erosion responded differently to FTCs. After seasonal FTCs, soil porosity increased (0.4 %-11.9 %) to some extent in all soils, with greater changes observed in the more eroded soils. Notably, capillary porosity exhibited a complex changing trend compared to total porosity. Degraded and parent soils showed a stable bulk density, while the original soil showed a decrease (2.1 %) in bulk density and the deposited soil showed an increase (18.4 %) in bulk density. With the increase of FTCs, the field capacity of original, degraded, and deposited soils exhibited a gradual decrease (15.1 %-18.5 %), while that of the parent soil slightly increased (0.9 %). After seasonal FTCs, the saturated hydraulic conductivity decreased for original and deposited soils (19.5 %-41.5 %), while it increased for degraded and parent soils (29.2 %-41.6 %). Throughout the FTCs, the proportion of the large aggregates decreased and the small aggregates increased, and the transformation was greater on the less eroded soils. The mean weight diameter and geometric mean diameter of the soils gradually decreased with increasing FTCs, while the change was smaller for the more eroded soils. After seasonal FTCs, the less eroded soils were at greater risk of erosion. Our results demonstrated that the number of FTCs had a more significant impact on soil physical properties compared to the temperature difference and soil water content. Overall, freeze-thaw action reinforced the spatial heterogeneity of soil properties, potentially intensifying soil erosion. These findings help reveal the effects of FTCs on the physical properties of soils with different degrees of erosion and deepen the understanding of the mechanism of FTCs on soil erosion processes.

中文翻译：

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东北地区不同程度侵蚀和季节冻融循环土壤物理性质响应


冻融循环（FTC）引起的土壤孔隙和团聚体稳定性的变化是融雪期间土壤侵蚀加剧的重要原因。土壤侵蚀导致土壤的空间重新分布，增强土壤异质性并可能影响土壤对 FTC 的响应。尽管如此，对于遭受不同程度侵蚀的土壤对季节性 FTC 的反应知之甚少。为了揭示季节性FTC的影响，测量了四种不同侵蚀程度（原始土、退化土、沉积土和母土）土壤孔隙特征和团聚体的动态变化，并分析了影响因素与土壤性质之间的联系。结果表明，FTCs改变了土壤结构，削弱了土壤的抗侵蚀能力，不同侵蚀程度的土壤对FTCs的反应不同。季节性 FTC 后，所有土壤的土壤孔隙度都在一定程度上增加了 (0.4%-11.9%)，在侵蚀较严重的土壤中观察到的变化更大。值得注意的是，与总孔隙度相比，毛细管孔隙度表现出复杂的变化趋势。退化土壤和母土表现出稳定的容重，而原始土壤表现出容重下降（2.1%），沉积土壤表现出容重增加（18.4%）。随着FTC的增加，原始土、退化土和沉积土的田间持水量逐渐减少（15.1%-18.5%），而母土田间持水量略有增加（0.9%）。经过季节性 FTC 后，原始土壤和沉积土壤的饱和导水率下降 (19.5 %-41.5 %)，而退化土壤和母土的饱和导水率则增加 (29.2 %-41.6 %)。 在整个 FTC 中，大团聚体的比例下降，小团聚体的比例增加，并且在侵蚀较少的土壤上转化更大。随着FTC的增加，土壤的平均重量直径和几何平均直径逐渐减小，而侵蚀程度越严重的土壤变化越小。季节性 FTC 后，侵蚀较少的土壤面临更大的侵蚀风险。我们的结果表明，与温差和土壤含水量相比，FTC 的数量对土壤物理性质的影响更为显着。总体而言，冻融作用增强了土壤性质的空间异质性，可能加剧土壤侵蚀。这些发现有助于揭示FTCs对不同侵蚀程度土壤物理性质的影响，加深对FTCs对土壤侵蚀过程机制的认识。