The impact of freeze-thaw cycles and soil moisture content at freezing on runoff and soil loss

The freeze-thaw (F-T) cycles play an important role in soil erosion, although quantitative description of this effect is challenging due to the complicated interactions of soil moisture content (SMC), surface hydrology, and flow hydraulics involved in processes of erosion. In this study, we investigated the influences of F-T cycles and SMC at freezing on runoff and soil loss under simulated rainfall in the U.S. Department of Agriculture Agricultural Research Service National Soil Erosion Research Lab. The SMCs at the start of freezing were adjusted to 10% and 20%, undergone 1, 3, and 6 F-T cycles with freezing at -12 degrees C for 24 hr and followed by thawing at 4 degrees C for 24 hr. After designed F-T cycle, the air-dried soils were packed into the 0.5-m-long, 0.2-m-wide, 0.1-m-deep soil boxes and subjected to simulated rainfall. The results showed that the impact of 20% SMC was greater than that of 10% SMC under the same F-T cycles and rainfall intensities. The impact of F-T cycles on runoff and soil loss increased with the number of F-T cycles at 10% SMC. However, at 20% SMC, the impact on runoff and soil loss increased after 1 and 3 F-T cycles and declined after 6 F-T cycles. Furthermore, the impact of SMC on runoff and soil loss was greater than the impact from different F-T cycles. This research fills a gap in the current literature on Alfisols affected by the F-T processes, and results are useful in the assessment of runoff and soil loss in regions where winter processes are significant.