Current issue: 54(2)
Soil frost from the winter 1941-1942 was of a special form. To create such a strong soil frost there need to be capillary soil form and long period of permanent and intense cold, meaning minus temperatures. The frost layer was thicker than normally.
Such a frost causes many problems on the fields and roads when the soil rises because of the frost and then falls unevenly back when the frost melts.The PDF contains a summary in Finnish.
The article presents some basic elements of soil frost and its occurrence. The data contains observations from different regions and soil types in Finland. Different forms of soil frost and factors affecting its formulation are discussed.The article concludes with the factors effecting soil frost. There are three issues. By the single grain soils the water content determines whether the frost becomes massive or layered. The structure of soil determines the occurrence of hollow formed frost. Within the soils with crumb structure both layered and hollow formed frost may occur. Layered frost may occur in soils with homogeneous crumb structure in which two kinds of ice layers occur: irregular and solid. The hollow-formed frost may occur in locker soils.
The winter 1986–87 was unusually cold; the snow cover remained thin and consequently the soil froze to a considerable depth. In spite of the severe frost, the lowest temperatures measured at the ground surface was -10.3°C and in the soil at the depth of 10 cm -5.8°C. The temperature sum of the following summer was unusually small and the soil frost melted more slowly than usual. The winter frosts did not have a decisive influence on the survival of planted seedlings.
The PDF includes an abstract in English.
During the next decade there will be a marked increase in the allowable cut in drained peatlands. At the same time, the mechanization in logging proceeds, and in short-distance haulage the use of forwarders will increase. This study, based on literature and some observations, deals with logging conditions in drained peatlands with special reference to the suitability of heavy logging machines for use in such terrain. In addition, soil frost and the bearing capacity of the frozen peat soil were studied.
Freezing of the soil in a drained peatland area depends prevailingly on the weather conditions during early winter. The factors influencing soil freezing of a drained peatland are completely different from those regulating the freezing of natural peat soils. The frost penetrates in general deeper in the drained than virgin peatland. The topmost peat layer does not, however, freeze uniformly. Generally speaking, the bearing capacity of a drained peat soil is lower than that of undrained peat due to lower water content.
It is concluded that heavy logging machines are probably not fitted for use in drained areas on peatland even if the average soil frost values recorded would suggest it. Moreover, because of their extremely superficial root systems, peatland forests are exposed to damages by heavy machines in thinning operations.
The PDF includes a summary in English.
The paper describes the results obtained from an investigation into the effect of thinning of different intensity and fertilization on the depth and water equivalent of the snow cover as well as on the depth of the soil frost in a young Scots pine (Pinus sylvestris L.) stand growing on drained peatland in Central Finland. Thinnings and fertilization was carried out in 1968, and the snow cover was followed in the winters 1970/71 and 1971/72.
Only extremely heavy thinnings (60% of the volume) seemed to increase the depth and water equivalent of the snow cover. The indirect effect of fertilization on the snow cover was insignificant. In the clear-cut sample plot of the study, soil frost was either not found at all or the depths of the frozen soil layer was smaller than in the other plots. When deciding the silvicultural measures to be taken in the case of tree stands growing on drained peatlands, there seems to be reason to avoid radical thinnings. Otherwise, the favourable influence of the trees on a site on its water relationships will be diminished.
The PDF includes a summary in English.