Current issue: 55(3)
Under compilation: 55(4)
In this investigation was studied 1) Volume growth and yield of timber in managed Norway spruce (Picea abies (L.) Karst.) forests under different rotations. 2) Value growth, net forest income and soil expectation value of managed forests under different rotations, and 3) The rotations of spruce forests managed on different rotation principles. The data was collected from Oxalis-Myrtillus type forests in South-West Finland.
Two developmental series of stands were constructed for the research, one of which were of better sites than the other. Sample plots were pure, even-aged spruce stands in well-managed forests. The stands had been thinned from below. The age varied from 25-30 years to the age of final cutting.
According to the study, in the artificially regenerated spruce stands the highest mean annual volume growth, 9.7 m3/ha, and also the highest net annual income of 14,50 Finnish marks/ha (calculated from average stumpages) was reached in rotation of 70 years. In the other managed spruce forests a mean annual volume growth of 6.6-8.8 m3/ha and the net annual income of 10,500-14,500 Finnish marks/ha were reached in the rotation of 70-100 years. The rotation for the maximum mean annual volume growth varied in the different series between 67-92 years. The maximum mean annual forest rent was only achieved in series B in a rotation of about 100 years, and in a naturally normal stand in a rotation of about 120 years. The intensity of thinnings and silviculture had a greater effect on value growth and on net income than on volume growth.
The PDF includes a summary in English.
The aim of this paper was that of studying the optimum growing schedules of forest stands, with the classic Faustmann formula as starting point. The study is mainly theoretical in nature. The study shows that the net present-value of the future revenues from a forest stand can be calculated, not only by means of the harvesting revenues, but also by a more theoretical concept, here termed the current gross soil rent. The current gross soil rent represents the difference between the current value growth and the rent of the growing stock.
By use of the concepts described here, it is theoretically possible to find the growing schedule for the stand which maximizes the net present-value of the stand. To make the formulae simpler, a one-year period has been adopted for discussion of the concepts involved in determination of the optimum structure and density of the growing stock, and the financial maturity. However, these concepts can be extended to cover periods of any length.
The method for determination of the optimum growing schedule for a forest stand can be summarized as follows: Thin the stand as the internal rate of return on the marginal increase in ’timber capital’ falls below the guiding rate of interest. Clear-cut and regenerate the stand as the internal rate of return on the sum of the ’timber and soil capital’ falls below the guiding rate of interest.
The PDF includes a summary in Finnish.