Silva Fennica vol. 4 no. 4 | 1970

Seed development was microscopically studied after controlled pollinations. In all the interspecific crosses incompatibility occured. In the following crosses the growth of all the pollen tubes stopped before they had penetrated through the nuclear cap: Picea abies (L.) Karst. x mariana, abies x jezoensis (and the reciprocal), abies x omorika (and the reciprocal), mariana x asperata, mariana x jezoensis and Picea abies x Pinus sylvestris L.

Some of the eggs were fertilized in the crosses Picea abies x glauca (and the reciprocal) abies x asperata, abies x koyamai, abies x obovata, mariana x omorika and jezoensis x omorika. Embryo degeneration was observed in all these crosses. All the embryos died in the crosses abies x glauca (and the reciprocal) as well as jezoensis x omorika. Adequate amounts of full seed for germination test was obtained from the crosses abies x asperata, abies x koyamai and abies x obovata. In all these crosses there were seeds which were able to germinate and the hybrids are now one growth season old.

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• Mikkola, E-mail: lm@mm.unknown

The goal of this study was to develop a mathematical model for determination of the optimal winching distance in different conditions as based on harvesting costs. In the thinned forest the strip roads are parallel and the winching routes perpendicularly to them. A directed felling of trees is used so that it is easy to make loads to be winched. The stems can also be prepared to timber assortments on the stump area and gathered to loads for skidding alongside the winching routes.

After winching the timber is transported using a forwarder mowing on the strip roads. If the stems have not been bucked in the forests, they are to be prepared to timber assortments before the following transportation, because the problem of turning whole stems in a thinned forest has not yet been solved.

In the mathematical model the formation of the costs was described using 18 variables of which 15 had an effect on the optimum winching distance. Some empirical values were estimated concerning these variables, and the corresponding optimum winching distance were computed. The optimum was mainly determined by the quantity of timber harvested per unit area, the size of the winching load, the regression coefficient of the times which were depended on the winching distance.

According to the model, the deviation from optimum winching distance does not cause a very great change in the analysed total costs. When the winching distance is longer, the increase of the costs is smaller than if it is shorter than optimum. In general, the increase of the costs was so small that in practice one obviously can be satisfied with rather approximate methods in determining the suitable winching distance.

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• Kärkkäinen, E-mail: mk@mm.unknown

The study attempts to establish to what extent the present regional allocation of the forest improvement subsidies equalize the profitability of forest drainage in Finland. The benefit/cost ratio has been used to describe the regional variation of the profitability

The study revealed that the forest improvement subsidies granted in 1968, even the highest possible subsidies, did not equalize the profitability of forest drainage. According to the results, the northern regions are at a disadvantage compared to the southern parts of the country. To fully equalize the profitability of forest drainage the average subsidies granted in 1968 should have been raised in the second financing zone from 22 to 32%, in the third zone from 32 to 60%, and in the fourth, northernmost zone from 43 to 86%. The study also suggests that the boundary lines of the financing zones should run, at least in Central and Northern Finland, from southeast to northwest instead from east to west, as it is now.

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• Numminen, E-mail: jn@mm.unknown

Under the soil bank act, which took effect in 1969, 85,000 hectares of agricultural land were withdrawn from agricultural production in order to cut down the heavy surpluses of grain and butter in Finland. The farmers have a possibility to afforest their soil bank land partly on public funds, and if they choose to do so they receive a compensation of 250 Fmk for 15 years, instead of the nine years which is the maximum duration of a soil bank contract.

The study involved interviewing of 136 farmers sampled from the total of 13,368. The farmers were planning to afforest a total of 18,600 ha by the end of 1972. The main species were birch (Betula sp.) 40%, Norway spruce (Picea abies (L.) H. Karst.) and Scots pine (Pinus sylvestris L.) both 30%. The main reasons (mentioned by 65% of the farmers) for afforestating the soil bank land were the unfavourable conditions for agriculture. On the other hand, 43% of those who had decided not to afforest felt that their land is too good to be planted with trees. One fifth of those not afforesting said that they themselves would not benefit from the afforestation and therefore were not interested in investing in forestry. The attitudes of the farmers seem to have also influenced their decision on afforestation. Those who had taken a positive decision on afforestation appeared to take more positive attitude in regard to forestry than other farmers.

The soil bank act does not seem to solve permanently Finland’s problem of the surpluses of agricultural products since the soil bank farmers planned to revert two thirds of the soil bank land under cultivation on the expiration of the soil bank act.

The PDF includes a summary in English.

• Numminen, E-mail: jn@mm.unknown