Acta Forestalia Fennica vol. 77 | 1964

The most important fact to consider in attempting to develop an increment forecast method is the great dependency of the increment on the growing stock volume. Although the site (soil and climate) produces the increment and volume, there would be no increment without the volume as an increment capital. The cutting possibilities are still more dependent on the existing growing stock. Thus, the primary characteristics in management planning is the growing stock volume. The methodological starting point in this paper is that the increment is considered dependent variable which can be explained by other growing stock characteristics. The basis of the analysis and the primary object of this investigation is the increment percentage. Using available and measured sample plots the increment percentage will be analysed as a dependent variable by other growing stock characteristics.

The main emphasis will be the methods which can be used in connection with the interacting increment and drain. An increment-drain forecast should give at least approximately the allowable cut in timber products. Thus, it will be attempted to find the stock characteristics determining the amounts of timber products.

The article introduces the theory and basic concepts of the increment-drain process, increment functions and basal area – height method, and discusses estimation of timber products in increment-drain forecast, fluctuations of the increment, mortality in connection with the increment-drain forecast, and the scheme of cutting budget for desirable growing stock. Finally, it gives some proposals, based on the investigation, for preparing an increment-drain forecast for a large forest area.

The PDF includes a summary in Finnish.

• Kuusela, E-mail: kk@mm.unknown

The purpose of this theoretical study was to define the factors related to wood production that affect the financial result of private forestry in Finland on the viewpoint of alternative calculation. The paper introduces the main concepts, analyses the outturn factors and discusses feasibility of some calculation methods, and finally draws up a business plan for a forest holding based on the chosen method.

In forestry, the quantitative and sustainability objectives for yield, the difference between annual proceeds and costs, and the capital value of the costs affect which factors are included in the calculation of profitability of forestry. The base-line situation for the alternative calculations is defined by an inventory. The future proceeds and costs are valuated and procedural models are formulated for the most advantageous alternatives. The main goal in private forestry is profit.

The PDF includes a summary in German.

• Einola, E-mail: je@mm.unknown

Prescribed burning is a common silvicultural practice in northern Europe, intended to destroy the slash and ground vegetation and to reduce the thickness of the raw humus layer prior reforestation. The purpose of the experiments was to study whether there are any differences in the commencement and early development of mycorrhizal infection between burned and unburned areas. A clear-cutting area was burned on May 1961. The soil was rocky moraine, the forest type was Vaccinium type. Two weeks after burning Scots pine (Pinus sylvestris L.) was sown in patches.

According to the results, mycorrhizal infection took place on the unburned area earlier than on the burned. The difference was relatively small, perhaps 1–2 weeks. Although burning kills mycorrhizal fungi, it did not cause serious harm to the seedlings, on the contrary, the favourable influence of burning was more distinct. The high temperatures caused by the fire are restricted in the soil in a prescribed burning only a few centimetres deep. Although the mycorrhizal fungi are concentrated in a very thin surface layer of the soil, some mycorrhizae are situated deeper, and from there the fungi are able to infect roots and spread back to the surface layer. The fire also rises the pH of the soil, which can be harmful for mycorrhizal fungi. Even this effect, however, is limited to a thin surface layer.

The PDF includes a summary in Finnish.

• Mikola, E-mail: pm@mm.unknown
• Laiho, E-mail: ol@mm.unknown
• Eerikäinen, E-mail: je@mm.unknown
• Kuvaja, E-mail: kk@mm.unknown

Mycorrhizal association is a characteristic feature of the trees of the northern coniferous forests. The purpose of the present study was to determine what influence some fungicides and herbicides regularly used in Finnish nurseries have on formation and development mycorrhizal in Scots pine (Pinus sylvestris L.) and Norway spruce (Picea abies (L.) H. Karst.) seedlings. The results are based mainly on field experiments in nurseries. First the initiation of mycorrhiza was described in untreated seedlings.

In the first growing season mycorrhizal infection commences fairly late even under normal conditions, i.e. 6–7 weeks after seeding and 3–4 weeks after the formation of the first short roots. Soil disinfectants are commonly used in nurseries before seeding, and they are supposed to evaporate or disintegrate in a few days or 1–2 weeks. In pure culture experiments mycorrhizal fungi proved several times more sensitive than parasitic and indifferent soil moulds to herbicides and fungicides, but in field experiments the delay of mycorrhizal infection caused by them does not seem to harm the seedlings. In the second summer differences of mycorrhizal relations between treated and control plots disappeared. Accordingly, the influence of biocides on mycorrhizae, when applied in the customary concentrations, does not extend beyond the first growing season.

Methyl bromide and SMDC retarded mycorrhiza formation distinctly, while formaldehyde and allyl alcohol had no effect. Apart from not retarding mycorrhizae, formaldehyde and allyl alcohol promoted seedling growth and favoured Trichoderma viride in the soil. Trichoderma is known to be antagonistic to many fungi.

The PDF includes a summary in Finnish.

• Laiho, E-mail: ol@mm.unknown
• Mikola, E-mail: pm@mm.unknown

The present study deals with correlation between level of ground water table and water content of peat in peatlands drained for forestry. The results have been obtained partly from field studies and partly from experiments in the laboratory.

Both the field and laboratory experiments proved that a close rectilinear correlation exists between the level of the ground water table and the water content of surface peat. A given change in the level of the ground water table corresponds to a smaller change in the water content the deeper the peat layer examined is situated. The change in the water content in the surface layer (0–20 cm) in the cases studied was of such a magnitude that a change of 10 cm in the level of the ground water table corresponded to a change of about 5 volume per cent. In deeper layers the change was smaller. The state of equilibrium regulating the water content of the peat is relatively stable. It is possible that the so-called optimum drainage of a peatland for each tree species can be theoretically determined on the basis of the correlation between the water content of peat and the level of ground water table.

The method used in the study, the repeated weighing of peat samples in their original place, has proved to be very useful and decisively better than the method based on one-time samples. The experiment also indicate that the correlation can be determined with laboratory experiments.

• Heikurainen, E-mail: lh@mm.unknown
• Päivänen, E-mail: jp@mm.unknown
• Sarasto, E-mail: js@mm.unknown