Purpose Freeze-thaw cycles (FTCs) can significantly impact aggregate size and integrity, subsequently influencing soil quality and soil productivity. Nevertheless, how to quantify the impacts of FTCs at different initial conditions on soil aggregates is challenging due to the complex interactive response and the difficulty to match in the field. In this study, the size composition, variability and stability were measured to evaluate the effects of FTCs on soil aggregates under different initial conditions. Materials and methods 8 FTC treatments (0, 1, 3, 5, 7, 10, 15 and 20 FTCs), 5 initial soil water contents (100, 200, 300, 400 and 450 g kg− 1), 4 eroded soils (original, degraded, deposited and parent), 2 freezing temperatures (-10 and − 15 ℃) and 2 initial bulk densities (1.2 and 1.3 g cm− 3) were employed to comprehensively quantify the impacts of FTCs on aggregate characteristics. The research focused on the typical black soils of Northeast China, a crucial agricultural zone that experiences frequent FTCs. Results and discussion Repeated FTCs had a cumulative effect on soil aggregate characteristics, but generally entered a steady state after 10–15 FTCs. Soil aggregates exhibited strong disruption by the first 5 FTCs. Throughout the FTCs, the distribution of aggregates of different sizes changed, with the proportion of large aggregates decreasing (decrement = 0.1% ~ 9.9%) while small aggregates increased (increment = 0.1% ~ 28.4%). Interestingly, the final size composition of aggregates was the combined result of the effects of fragmentation and generation. The aggregates of the deposited soil showed the greatest variability; moreover, the higher the water content, the lower the freezing temperature and the higher the bulk density, the more variability the soil aggregates. In contrast, the deposited soil had the lowest stability after the FTCs. High water content (> 300 g kg− 1) and low temperatures leaded soil instability, while high bulk density could increase soil stability. Finally, the degree of erosion was the most important factor influencing soil aggregate characteristics (contributing 50.4%). Conclusions These findings revealed the dynamic variations of aggregate characteristics used in the assessment of the effects of FTCs on aggregates and provided new insights into mechanisms of erosion caused by FTCs from the perspective of soil aggregate changes.

Responses of soil aggregates to freeze-thaw cycles under simulated experiments in typical black soils of Northeast China

期刊论文
发表日期：

2025年3月8日

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Guopeng Wang,
Zhuodong Zhang,
Keli Zhang

摘要

Purpose

Freeze-thaw cycles (FTCs) can significantly impact aggregate size and integrity, subsequently influencing soil quality and soil productivity. Nevertheless, how to quantify the impacts of FTCs at different initial conditions on soil aggregates is challenging due to the complex interactive response and the difficulty to match in the field. In this study, the size composition, variability and stability were measured to evaluate the effects of FTCs on soil aggregates under different initial conditions.

Materials and methods

8 FTC treatments (0, 1, 3, 5, 7, 10, 15 and 20 FTCs), 5 initial soil water contents (100, 200, 300, 400 and 450 g kg^− 1), 4 eroded soils (original, degraded, deposited and parent), 2 freezing temperatures (-10 and − 15 ℃) and 2 initial bulk densities (1.2 and 1.3 g cm^− 3) were employed to comprehensively quantify the impacts of FTCs on aggregate characteristics. The research focused on the typical black soils of Northeast China, a crucial agricultural zone that experiences frequent FTCs.

Results and discussion

Repeated FTCs had a cumulative effect on soil aggregate characteristics, but generally entered a steady state after 10–15 FTCs. Soil aggregates exhibited strong disruption by the first 5 FTCs. Throughout the FTCs, the distribution of aggregates of different sizes changed, with the proportion of large aggregates decreasing (decrement = 0.1% ~ 9.9%) while small aggregates increased (increment = 0.1% ~ 28.4%). Interestingly, the final size composition of aggregates was the combined result of the effects of fragmentation and generation. The aggregates of the deposited soil showed the greatest variability; moreover, the higher the water content, the lower the freezing temperature and the higher the bulk density, the more variability the soil aggregates. In contrast, the deposited soil had the lowest stability after the FTCs. High water content (> 300 g kg^− 1) and low temperatures leaded soil instability, while high bulk density could increase soil stability. Finally, the degree of erosion was the most important factor influencing soil aggregate characteristics (contributing 50.4%).

Conclusions

These findings revealed the dynamic variations of aggregate characteristics used in the assessment of the effects of FTCs on aggregates and provided new insights into mechanisms of erosion caused by FTCs from the perspective of soil aggregate changes.