Spatial and temporal variability in forest soil frost development in western Montana

Systematic sampling grids of methylene blue frost tubes were used to study temporal and spatial characteristics of soil frost development in a 1250 m elevation forest stand and adjacent clearcut in western Montana during the winter of 1985-86. The inverse relationship between snow accumulation and frost depth is very strong. Consequently, the influence of forest canopy on snow accumulation resulted in greater frost depth in the stands than in the adjacent clearcuts. There was a difference of almost 80 days in the timing of maximum frost depth between the two elevations. Relative variability in frost development (indicated by the coefficient of variation) was nearly identical and constant on the low site treatments, and very similar but not constant through the winter on the high site treatments. Frost will be gone before snow on the high sites. Snow was gone before thaw began on the low sites.