Submitted to: Book Chapter
Publication Type: Book / Chapter
Publication Acceptance Date: February 18, 2001
Publication Date: July 30, 2001
Citation: GATTO, L.W., HALVORSON, J.J., MCCOOL, D.K., PALAZZO, A.J. EFFECTS OF FREEZE-THAW CYCLING ON SOIL EROSION: APPLICATION TO MILITARY TRAINING LANDS. LANDSCAPE EROSION AND EVOLUTION MODELING, EDITED BY HARMON & DOE III, KLUWER ACADEMIC/PLENUM PUBLISHERS, NEW YORK. BOOK CHAPTER. 2001.
This chapter discusses the effects of soil freeze-thaw (FT) processes on soil erodibility and runoff erosivity via physical changes in soil-water content and redistribution, soil density and strength, infiltration and runoff, and soil-surface geometry with special emphasis on military training-land soils. Although, FT also affects the susceptibility of soil to wind erosion, this chapter addresses water-erosion processes only. The ice that forms in soil pores during freezing reduces soil density by pushing soil grains apart and reducing their interlocking. The amount of soil expansion depends on soil-water content when freezing starts, the volume of water drawn to the freezing zone, soil texture, the depth and rate of frost penetration, and the number of FT cycles. When soil ice thaws, the soil is less dense, less cohesive, and often nearly saturated. In this condition the soil is highly susceptible to mass failure on slopes and easily eroded by runoff. During maneuvers on training lands military vehicles damage vegetation, change soil surfaces, weaken soil aggregates, and compact and rut soils. The ruts can channel runoff which increases its transport capacity and its erosion potential. In this regard ruts are hydraulically similar to natural rills. The other maneuver impacts reduce infiltration, increase the volume and period of runoff, and increase soil erodibility. Research shows that FT cycling reduces vehicle compaction in soil, increases infiltration in vehicle ruts and changes the cross- sectional geometry of ruts and natural rills which can affect the sediment transport capacity of runoff. Thus, FT processes significantly influence soil erosion and landform evolution and must be adequately simulated in landscape models.