Articles containing the keyword 'yield tables'

Yield of Cupressus lusitanica Mill. was modelled by predicting the diameter distribution of trees at given stand ages. The beta distribution was used as a theoretical distribution. The models used for the calculation of diameter distribution were based on 66 temporal sample plots with varying age, site and stand density. The growing sites of Cupressus lusitanica were divided into four classes on the basis of age and dominant height. Using the stand models developed in the study, the yield and profitability of different thinning schedules was evaluated by a simulation technique. In the simulated treatment regimes, the mean annual increment varied from 6.6 m³/ha in the poorest site class to 16.6 m³/ha in the best class with rotation lengths ranging from 25 years (best sites) to 34 years (poorest sites). With typical planting densities (1,600 trees/ha), thinnings increase the total harvest by a few percentage points and improved the profitability of plantation forestry.
The PDF includes an abstract in Finnish.

• Pohjonen, E-mail: vp@mm.unknown
• Pukkala, E-mail: tp@mm.unknown

Silva Fennica issue 52 includes presentations held in professional development courses, arranged for foresters working in public administration in 1938. The presentations focus on practical issues in forest management and administration, especially in regional level. The education was arranged by Forest Service.

This presentation describes different methods of assessing tree growth.

• Ilvessalo, E-mail: yi@mm.unknown

One of the difficulties in constructing growth and yield tables has been to determine which of the sample plots growing the same tree species and belonging to the same forest site type, with reference to the quality of stands, have to be included in the same growth series.

New growth and yield tables for the most important tree species were constructed in Finland in 1916–1919, using new principles that aim at avoiding some of the common weaknesses. There were two main differences to the earlier work. First, the site quality class (forest site type) was determined for each sample plot when the sample plot was measured, independently of the stand occupying the site. In this way it was possible to treat the sample plots of each site as an independent group from the beginning, and so that the quality classes were the same for all the tree species. Second, mathematic-statistical methods were used to deduct the so-called stem frequency distribution series, when studying which of the sample plots of the same quality class belong to the same growth series. They represent the average number of stems of the different diameter classes. A more detailed description of the method used to create the growth and yield tables is published in Acta Forestalia Fennica no. 15.

In the PDF is included a summary in Finnish.

• Ilvessalo, E-mail: yi@mm.unknown

The present study proposes to calculate the economic sequence of two of Finland’s three main tree species, Norway spruce (Picea abies (L.) H. Karst.) and silver birch (Betula pendula Roth) when planted on Oxalias-Myrtillus type sites where both species are equally suitable, on biological grounds. In addition, the accuracy and applicability of the present Finnish yield tables to an economic comparison is tested. Benefit/cost ratio was selected as criterion of profitableness. All future net incomes and costs were discounted into the planting time and added together. The ratio between the discounted net revenues and the discounted investment costs (later called profit ratio) was the criterion. There is no reliable method to forecast the future wood prices, therefore two price ratios, birch veneer timber to spruce pulpwood and birch cordwood to spruce pulpwood, were chosen as free variables. The economic sequence of the tree species was determined as the function of these variables.

The main conclusions are, first, that under the present price ratios spruce appears to be the better choice for the forest owner, and the most promising policy for changing the situation seems to decrease the production costs of plants in birch nurseries. Second, the present Finnish yield tables are not consistent or accurate enough to enable any sufficiently reliable economic comparisons of tree species in artificial regeneration. The possible error of difference between two rather uncertain estimates is big. More work is needed to construct a uniform system of yield tables covering all main tree species, all site types, all macro climate conditions and all types of regeneration.

The PDF includes a summary in English.

• Keltikangas, E-mail: mk@mm.unknown
• Tiililä, E-mail: pt@mm.unknown

The article contains tree lectures given in the meeting of the Geographical Society in Finland on February 25^th 1921.  The titles of the lectures are I Forest types in general, II Forest types as a basis for new growth and yield tables in Finland, and III Other research on forest types.  

The first lecture is a follow-up of the Cajander’s 1909 published article on forest types. It deepens the theory on forest types. The classification into forest types represents primarily different plant communities of ground cover. The types are named after the characteristic plant species, indicator plants, however, many other species appear in different abundance.

The second lecture represents the research proceedings of mensuration of forest stands of different types to compile yield tables for pine.  The forest types differ from each other distinctly on their growing preconditions, but inside one class the variation of the growing conditions is so small, that the classification can be used for yield tables, determining the basis of taxation and for classification of forest based on height over age.

The third lecture is a summary of other studies about forest type classification.  They confirm the results presented in earlier lectures. 

• Cajander, E-mail: ac@mm.unknown
• Ilvessalo, E-mail: yi@mm.unknown

New growth and yield tables were prepared for Southern Finland. To finalize the tables, it had to be determined whether the forest site types developed by Cajanus could be used in mensurational research.

Comparative study was performed in 1916-1919 to study the growth of the trees in different forest site types. Total of 467 sample sites were measured in Southern and Central Finland. All the forest site types were found to have a distinctive vegetation typical to the site. It can be concluded that the ground vegetation can be used to determine the forest site type. The growth of trees was different in different forest site types, yet similar within each site type. The forest site types are uniform, natural and easy to determine, and can thus be used to classify the forest stands and used in mensurational research and a basis to growth and yield tables.

The PDF includes a summary in German.

• Ilvessalo, E-mail: yi@mm.unknown

The aim of the study is to generate yield tables that enables calculating the stumpage values of the forests in different ages. The article investigates the diameter distribution of a stand at the breast height and their changes with the age of the stand.  In an even-aged stand the calculating of the stumpage value is based on height and breast height diameter. Hence the diameter distribution of a stand determines the stand volume, the stem frequency distribution series can be used as the basis of compiling the yield tables, in which the volume is the main factor.   

The study is based on spruce and pine mensuration data from Finland, pine stands from Prussia, and spruce stands from mountainous area of Switzerland. The article presents the characteristics of stem frequency distribution series based on the data. The studied characteristics are arithmetic middle, dispersion, asymmetry (skewness) and excess.

It can be recommended to create tables that show the different developments for age classes. Based on such tables the expected value of the stand can be calculated in practical forest management. Determining a general value of a stand in different forest site types would be important for forest valuation and forest statistics.    

• Cajanus, E-mail: wc@mm.unknown

The study is based on research in Germany, Austria, Switzerland, north Russia and Siberia, and Finland in years 1906-1908. The objective of the study is to find means to create forest site classes or forest types to direct practical forest management.

The article presents the classification of forests into site classes (Oxalis-Majanthemum type, Myrtillus type, Vaccinium type and Calluna type). The second part of the article represents different methods to calculate growth and yield tables for different forest site types. The conclusion of the study is that forest areas with similar vegetation and forest type can be handled in one way for forest management. 

• Cajander, E-mail: ac@mm.unknown

This study is concerned with silvicultural selection from above. The material consists of 18 Scots pine (Pinus sylvestris L.) sample plots in the southern half of Finland in experimental forests. The method is motivated by the great difference between the stumpage prices of saw timber and pulpwood. The method suggested includes the removal of individuals belonging to the predominating canopy, to achieve high levels of income from the stand at an early stage. The method is applied at when the growing stock is attaining saw-timber size. Before that the stand is treated with thinnings from below. It is supposed that the volume of growing stock is maintained at a level as high as that in below-thinned stands, and that rotation is of normal length.

On the average, the increment in basal area, as well as volume increment, is greater in stands selectively cut from above than in those treated with low thinnings of the same degree. Initially, selection from above seems to exert a negative effect upon the development of dominant height; later, the dominant height reassumes the same rate of increment as in the below-thinned stands. Selection from above also means an increase in saw-timber production, although it involves a reduction in the mean size of saw timber. The investigation includes growth and yield tables for pine stands treated with silvicultural selection from above.

The results of the investigation prove that silvicultural selection from above is at least as profitable as low thinning. This provides freedom for stand treatment, and contributes to the application of a method most suitable for the owner in each individual case. It is further stressed that the maintenance of a high wood capital in the stand is far more important than the method of thinning applied.

The PDF includes a summary in English.

• Vuokila, E-mail: yv@mm.unknown