Shigeo Watanabe

Experiment on Snow Crown of Japanese Larch (2)

A comparative observation of the weights of snow crown was made on test larch trees 15, 25, 42 and 53 years in age. As a result of the comparison of the weights of snow crown in terms of load per unit area shaded by crown, any difference in weight of snow crown due to the difference in tree age could not be ascertained clearly, and as far as the 15, 25 and 42 years old trees are concerned, the weight of snow crown seemed to increase or decrease in relation to the length of branches and twigs. In the case of the 53 years old tree showing the largest weight of snow crown among all the test trees, it was found that drooping of limbs with increasing weight of snow crown was slow and the duration in and near a drooped condition when the unit shaded area becomes largest was by far longer than other test trees younger in age.

Snow cover on planted land at the heavy-snow area.

The purpose of this investigation is to make clear the states of snow cover in the heavy-snow area of which Cryptomeria japonica-trees are damaged by snow pressure very often. Gomisawa Plantation, young stands of C. japonica is in the heavy- snow area of Niigata Prefecture. On the various topographic places of this plantation, maximum snow cover depth, snow pressures and the vertical section of snow cover were investigation in the snow seasons of the years 1965-1969. The results are as follows : 1) The course of snow cover depth during each winter at Gomisawa has a strong resemblance to that of Tokamachi Site.2) It seems that the heavy-snow year over 500 cm in maximum depth on the flat stand occurred five times within last twenty years.3) It is estimated that the duration of continuous snow cover range 160-190 days on the flat stand.4) The maximum snow cover depths are considerably changed with topography, wind direction and climatic condition in each winter. They range from 310 to 750 cm or more in the heavy-snow year, and from 290 to 470 cm in the year of small depth. In addition, always they are shallow on the windward slopes, and are deep on the leeward slopes. Therefore, the snow pressures on inclined stands show remarkably large values onthe leeward slopes. The settling pressures of snow on flat stands range from 2.4 to 3.0 times as great as those of Tokamachi Site.The states of snow cover mentioned above are closely related with the damage of the forests.

Experiment on the Snow Crowm of Japanese Larch (1)

A series of experiments have been continued in order to realize the silvicultural management for the prevention of forest damage caused by the weight of snow crown. This paper deals with the study about the snow crown on the trees of Japanese larch, during the snow season of 1964-1965.The equipment of experiment is shown in Photo. 1 and 2.As the result, following points were made clear : The process of snow crown on Japanese larch was similar to that on Japanese cedar, but the crowned state did not continue over a few days. The maximum quantity of snow crown, in the ordinary conditions of snowfall, occurred on the case when the amount of precipitation was about 20 mm.