The effects of freeze-thaw cycles at different initial soil water contents on soil erodibility in Chinese Mollisol region

Authors: WANG, LEI - Northwest A&f University; ZUO, XIAOFENG - Northwest A&f University; ZHENG, FENLI - Northwest A&f University; Wilson, Glenn; Zhang, Xunchang; WANG, YIFEI - Northwest A&f University; FU, HAN - Northwest A&f University

Submitted to: Catena
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 4/18/2020
Publication Date: 4/28/2020
Citation: Wang, L., Zuo, X., Zheng, F., Wilson, G.V., Zhang, X.J., Wang, Y., Fu, H. 2020. The effects of freeze-thaw cycles at different initial soil water contents on soil erodibility in Chinese Mollisol region. Catena. 193 pp. 1-11. https://doi.org/10.1016/j.catena.2020.104615.
DOI: https://doi.org/10.1016/j.catena.2020.104615

Interpretive Summary: Freeze-thaw action is a natural phenomenon in cold regions that affects the rate of erosion, defined as soil erodibility, by changing soil structure and the soil’s mechanical properties. However, quantifying the effects of freeze-thaw cycles (FTCs) on soil erodibility at different initial soil water contents (ISWCs) is difficult due to the complex responses of different soil properties. In this study, direct shear strength and soil disintegration tests were conducted to quantify indicators of soil erodibility. Seven FTCs (0, 1, 3, 5, 7, 10 and 13) and three ISWCs (16.5, 24.8 and 33.0%) were employed to investigate soil shear strength behavior and disintegration properties for two Mollisol (dark, organic rich topsoil) soils. Results showed that repeated FTCs had impacts on soil mechanical properties that accumulated over time such that by the 10th FTC the threshold soil erodibility was impacted. The soil shear strength decreased by 1.1% to 15.1% and by 9.2% to 30.5% for the two soils under four different normal stresses over the 13 FTCs as compared to no freeze-thaw treatment. Soil cohesion generally decreased with the increase of FTCs. Soil internal friction angle showed no trend with FTCs at the 16.5% and 24.8% water contents but a decreasing trend at the 33.0% water content which corresponds to field capacity. Soil disintegration rate increased with FTC and reached a maximum value at the 10th cycle but decreased with the increase of ISWC. Soil disintegration of the two Mollisols showed a sharp disintegration of about 60% in 133 seconds. Relationships were found between soil erodibility indicators and FTCs. This study provides a new understanding of the response of erodibility of Mollisols to freeze-thaw cycles.

Technical Abstract: Freeze-thaw action is a natural phenomenon in cold regions, which affects soil erodibility by changing soil structure and mechanical properties. However, quantifying the effects of freeze-thaw cycles (FTCs) at different initial soil water contents (ISWCs) on soil erodibility is challenging due to the complex interactive soil mechanical responses. In this study, direct shear strength and soil disintegration tests were conducted to quantify soil erodibility indices. Seven FTCs (0, 1, 3, 5, 7, 10 and 13) and three ISWCs (16.5, 24.8 and 33.0%) were employed to investigate soil shear behavior and disintegration properties for two Mollisol soils. Results showed that repeated FTCs had cumulative impacts on soil mechanical properties, and the 10th FTC might be the threshold number for influencing soil erodibility. The soil shear strength decreased by 1.1%-15.1% and 9.2%-30.5% under four normal stresses at the first and 13th FTCs for these two soils, compared with no freeze-thaw treatment. Soil cohesion generally decreased with the increase of FTCs. Soil internal friction angle showed no trend with FTCs at the 16.5% and 24.8% water contents but a decreasing trend at the 33.0% water content (field capacity). Soil disintegration rate increased with FTC and reached a maximum value at the 10th cycle but decreased with the increase of ISWC. Soil disintegration of the two Mollisols showed a sharp disintegration of about 60% in 133 s. Relationships were found between soil erodibility indices and FTCs. This study provides a new understanding of the response of erodibility of Mollisols to freeze-thaw cycles.