SCHRIFTENREIHE Institut für Pflanzenernährung und Bodenkunde ...

They explained that the meltwater percolating could occur on the unfrozen
topsoil even though snow was present. In fact, Hortonian surface runoff can
always find its way to infiltrate somewhere over a large region because soil might
be never frozen homogeneously considering spatial variability of soil properties.
Although the current freezing soil module has little effect on the simulations of
surface runoff, we expect a detailed study of the soil-atmosphere processes and
effects of boundary conditions to improve the surface runoff algorithm in the
freezing code.
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Simulation of Grazing Effects on Soil Freezing and Thawing
In addition to the effect of a frozen soil layer on the water and heat transfer
rates, land management also plays a key role in modifying soil hydraulic and
thermal parameters through changing soil structure (Hillel, 1998). Freezing
normally reduces the permeability of soils owing to the impeding effect of ice
lenses as well as structural changes. In the grazed sites with a poor-structured
soil (Zhao et al., 2008), freezing often leads to a higher level of aggregation
induced by dehydration and the pressure of ice crystals. In contrast to this, in the
ungrazed sites with a well-structured soil, expansion of the freezing soil may
cause the aggregates to break down.
In Zhao et al. (2008), soil hydraulic and thermal parameters were proofed to
be a function of grazing intensity under unfrozen conditions. For instance, the
van Genuchten hydraulic parameters θs, α, and Ks are smaller at the grazed
sites than those at the ungrazed sites due to the grazing-induced soil
compaction. However, it is possible that model parameterizations regarding
grazing effects differ between frozen and unfrozen conditions. As for the change
of hydraulic parameters under frozen condition, the blocking effect of hydraulic
conductivity is considered (Eq. 4). However, we can not modify water retention
parameters under frozen conditions based on the limited knowledge on how to
measure and finally parameterize this effect. It is known that soil heat capacity is
not sensitive to the modeling result given that it is straightforward calculated from
the material constituents and its volumetric heat capacity. Therefore, our method
is assumed as accurate parameterization of heat capacity. That is, soil heat