To select the suitable value for the sag-span ratio of the track cable, s, might be one of the important problems relating to design the logging cableway. After some numerical calculation, author gets a graph for the optimum value of the sag-span ratio, Fig. 1, in which the values of s just satisfy the safety conditions, one for the cable tension (safety factor N=3) and another for the ratio of wheel load to cable tention (allowable values r=1/24_??_1/48 according to the scale of cableways), and then another graph, Fig. 2, where the elastic elongation of the cable is taken into account. Further the optimum values of the basal tension ratios, the ratios of the empty cable tension to the loaded cable tension under the optimum conditions, are examined (see Fig. 3_??_5). Author also suggests a way to select the suitable values of the cable diameter, the carriage load and the sag-span ratio for the given span condition.

View full abstract

In 1962, a gamma field which belongs to the Institute of Radiation Breeding M. A. F. has been started its conventional operation for studing mutation breeding of agronomic plants. In this experiment, effects of chronic gamma-rays irradiation on flower setting of pines during April, 1962 to May, 1963 was investigated. It has been apparent that lethal dose rate of P. densiflora and P. thunbergii is about 17_??_18 r/day, and for flower setting the dose rates are ca. 9 r/clay and ca. 6 r/day respectively.
It was observed that, in 1962, female flower setting was seen in the range where dose rate is lower than 13.4 r/day and, in 1963, the inhibiting dose rate was reduced to ca. 9 r/day. Concerning the radiosensitivity of male and female flowers, the former seems to be a little more sensitivie to the, radiation. Germination percentage, percentage of ungerminated polleo and length of pollen tube were investigated with individually collected pollen in the gamma field, and no distinct gradient was observed in above mentioned traits owing to wide individual variation.

View full abstract

It is well known that treatment of gibberellic acid on Cryptomeria is very effective to bear flower buds. But the number, the ratio on sexual differentiation and the development of flower buds borne through the action of gibberellic acid are varied by many factors controlling the growth. The author reported the effects of soil moisture, fertillizer and photoperiod in the previous papers of this series.
In this work, effects of gibberllic acid to the growth and flower formation were studied on the seedlings grown under different conditions in density and fertilizing. In the spring of 1961, 1-year-old seedlings of Cryptomeria japonica were transplanted and grown under different conditions given in Table 1. Foliar spraying of gibberellic acid were made in the next year.
The effect of density and fertilizer on the growth was obvious as shown from Table 2 to 6. The rate of growth of each seedling measured on height, diameter, length of branch, fresh weight of shoot and fresh weight of subterranean parts were arranged roughly to the following orders from larger to smaller; fertilized NPK>fertilized PK>not fertilized and sparse> medium> dense.
The role of gibberellic acid was decisive for the flower formation. No spray resulted no formation of the flower buds. From Table 7 it will be seen that the flower buds born through the summer spray abounded in made one and those through the fall spray in female one. But the ratio on sexual differentiation of the flower was varied with other growing conditions. Under the poor fertilizing conditions, flower buds decreased in number and consisted of only female one. As shown by Table 8, there was no bearing of the flower buds on the twigs, which were branched from the lower part of the stem and stunted under the shadows by vigorous growing upper parts, such as N_D MNPK. From these results, an existence of close relations between the growing conditions and formation of flowers was clear.

View full abstract

It is well-known that the pine caterpillar (Dendrolimus spectabilis BUTLER) is the most injurious among the leaf-eating insects of the red pine (Pinus densiflora S. et Z.) and frequently gives the greatest damage to the red pine forest in Japan.
As the result of the feeding damage of only pine caterpillar, even if the red pine is not dead, it seems that the damaged tree has a small growth in comparison with the normal red pine, and, what is more, its damaged tree is apt to be infested with the pine bark beetles repeatedly. It is an important thing to know the effects of its feeding damage upon the growth of the red pine.
Therefore, the author made the feeding damage of the pine caterpillar reappear by means of artificial defoliation and observed its effects. This investigation was carried out in 1958_??_1960, and the artificial defoliation was conducted from May to July in 1958.
The results obtained from the investigation were as follows:
1. The artificial defoliation had influence on the diameter growth immediately after the defoliation, but on the height growth it exerted a great influence at the next year of the treatment.
2. Even if the individual was defoliated more than 90% of the needle-leaves, the withering happened few, namely, the withering was restricted within the individual defoliated nearly 100% of the needle-leaves. Although the most of defoliated red pines were continuing the growth, they had a small growth as compared with the non-defoliated.
That is, the percentage of both the diameter growth and the height showed about 40_??_50% of the normal for two years after the defoliation. When the percentage of the defoliation was below 60 or 70%, the growth percentage of treatmental tree was lower 10_??_20% than the normal for two years, but at the third year after the defoliation, these treatmental trees had little influence on the growth. In case of the heavier defoliation than 60 or 70%, the effects were remaining on the pine growth even after two years.
3. The stem growth was proportioned to the integrating leaf volume, so that, it seems that the leaf volume and the time that act on assimiration are closely related with the growth of the red pine.
4. If the red pine is not defoliated very heavily, at the third year after the defoliation, the treatmental tree will not have its influence, but it seems to be very difficult to recover the difference of the growth appeared for two years. That is, if the red pine is defoliated more than 50% of the needle-leaves only once, it seems to be impossible that its pine can recover the decline of the growth occurred for two years by the defoliation.

View full abstract