Abstract
It is wellknown that any type of ground cover reduces the depth of frost penetration. However, very few studies have been made to determine the actual extent by which a ground cover soil freezing and thawing.
In this report, the author deal with some investigations on the penetration of soil freezing and thawing in a bare ground, in a grassland (Sasa nipponica) and in a brushcutting area. This investigation was carried out in Kyoto University forest in eastern Hokkaido (lat. 43°01′, long. 143°58′, alt. 35-140m) during winters of 1977-78 and 1978-79.
The results obtained from this investigation were as follows;
1) In both winters, the maximum depths of frost penetration were extremely greater in a bare ground than in a grassland (Sasa nipponica) and the defferences were more than 20 cm.
2) The maximum frost depths did not vary a great deal between the bare ground and the brush cutting plots.
3) The depth of frost penetration (X2) into the soil covered with a heat insulating material might be presumed from the following equation,
X2= -S+√(S²+X²1)
S=30 cm : in a grassland (Sasa nipponica)
S=8 cm : in a brush cutting area
where X1 is the depth of frost penetration in a bare ground and S is a equivalent depth of frozen soil to a thickness of a heat insulating material in heat conduction.
