Articles containing the keyword 'metsänarviointi'

The concepts of the terms compartment and compartment-wise forest inventory have been studied empirically by repeated delineation and intensive systematic plot samples. The material consisted of 16 study areas of some 8–90 hectares in size in Southern Finland and of more than 1,000 relascope plots. Stands and compartments were found to be rather heterogenous. Alternative photographs, working techniques and test persons were studied. An endeavour for better accuracy in compartment inventories is recommended.

The PDF includes a summary in English.

• Poso, E-mail: sp@mm.unknown

18 permanent sample subplots of the Swedish and the Hassian Forestry Institute, each measured in equal intervals for several decades, were divided into subplots of different size. An analysis of variance was calculated for every set of subplot size. The development of intraclass-correlations over years and over different sizes of subplots could be explained if three different correlations were assumed: soil-correlation, correlations from irregular distribution of the trees, and correlation resulting from competition. Intraclass-correlations were positive or negative depending on dominance of one or two of these correlations.

An explanatory simultation study of competitional variance showed the effect of the degree of competitional correlations on the variance of means of subplots of different sizes. If this coefficient was small, all variances of subplots means within the range investigated became larger than expected in experiments without competition, with larger coefficients the variances of means of the smaller subplots became smaller, those of larger subplots larger than expected.

Plots of medium or large size are probably optimal for long term experiments with forest trees, if all sources of costs in such experiments are taken into account.

The PDF includes a summary in English and Finnish.

• Stern, E-mail: ks@mm.unknown

No other manifestation of life is allied more conspicuously to the theory of relativity as the growth of forest stands which is a function of the inherent growth potential of trees, the productive capacity of environment, and time.

The height over age quotient of a forest stand is usually the most reliable indicator of the productive forces of the habitat. Stem analysis have shown that increment of a tree at different ages is closely correlated with the extension of roots into individual geological horizons of different productive capacity. Growth curves of stands of a same tree species growing on different soils can be disparate due to different conditions. The temporal variety of tree growth on different sites is of prime importance in the construction of yield tables. Investigations of natural plant communities of Finland provided one rational approach towards the construction of yield tables. By confining mensuration analyses to define floristic types, the Finnish foresters harmonized their records with Einstein’s formula for space-time matrix of material events.

• Wilde, E-mail: sw@mm.unknown

In connection to the Third National Forest Inventory of Finland, two survey strips in the northernmost Finland were photographed on scale 1:15,000. Infrared films and a yellow filter were used. For the present experiment a total length of 66 km of the strips was photographed. The strips were surveyed visually from the ground by stands. Sample plots were measured at kilometre intervals. The aerial photographs were surveyed the distances covered in the ground. The work was aided by stereograms which showed 16 large-size sample plots localised on aerial photographs.

The main groups of land identified along the survey line were productive and poorly productive forest land, wasteland and another land, in addition, peatland and firm land were distinguished. Although some differences were noted, the two survey methods provided fairly similar results. For an estimation of the tree species composition the material is one-sided since the district is mainly Scots pine. The principal tree species was successfully distinguished on aerial photographs in 78 out of 82 comparable pairs.

The mean of ground observations of dominant height of the stands was 10.9 m, that of observations on aerial photographs 11.2 m. The result of stand volume estimates reveals a distinct correlation between the various methods of estimation.

In an earlier study it was shown that it is possible, using a stand volume table based on characteristics revealed in aerial photography, to create a general idea of stand volume on the southern half of the country. A few additional factors, of interest for the stratification necessary in forest inventories, were also studied. A distinct correlation was observed between the results of aerial and ground survey for all the characteristics discussed. The present experiment showed that the prerequisites for stratification through aerial photographs do exist. Further investigation is needed into the most appropriate methods for stratification in each situation.

The PDF includes a summary in English.

• Nyyssönen, E-mail: an@mm.unknown
• Poso, E-mail: sp@mm.unknown

• Kuusela, E-mail: kk@mm.unknown
• Setälä, E-mail: ks@mm.unknown

The study is continuation of the earlier structure and growth studies of Scots pine (Pinus sylvestris L.) and Norway spruce (Picea abies (L.) H. Karst.) in Forest Research Institute. The material represents birch stands (Betula verrucosa, now B. pendula, and B. Pubescens L.) in Southern Finland. The stands were treated with different fellings, and in regard to their silvicultural condition classified as good, satisfactory and unsatisfactory. Height of the trees, height of living crown, volume, increment and volume increment and development of stem diameter series was measured.

The most characteristic difference between the silviculturally good and poor stands was that the the annual increment of the good stands concentrated into large size trees, and the increment of unsatisfactory stands into small and inferior trees.

It is concluded that if the aim of stand treatment is to produce large and high quality volume increment, the most favourable stand volume of  birch stands, compared with naturally normal stand volume, seems to be 90-85% at the age of 41-55 years, and 80-70% at the age of 56-65 years. If growth of large size trees is aimed at, the maximum number of the dominant trees per hectares cannot be more than 400 at the age of 50-60 years.

The article includes a summary in English.

• Kuusela, E-mail: kk@mm.unknown

Silva Fennica Issue 69 includes presentations held in 1948-1950 in the fourth professional development courses, arranged for foresters working in the Forest Service. The presentations focus on practical issues in forest management and administration, especially in regional level. The education was arranged by Forest Service.

Forest Service begun the aerial mapping of the state forests in northern Finland in 1948. This presentation describes the state of the work, practices and methods of the work.

• Olenius, E-mail: lo@mm.unknown

The article is a treatise on use of aerial photography in forestry and its prodpective applications in Finland, based on the writers visit to Techniche Hohschule Dresden in Germany and experiences in his work in Forest Service.

Optimal conditions and principals of aerial photography are described. There is potential in use of aerial photography in Finland. The terrain is relatively flat, and large areas, especially in Lapland, are inadequately mapped. However, to fulfil the current requirements for forest maps, aerial photography should be carried out as aerial stereo photography at a sufficiently large scale. At a certain scale terrain survey becomes cheaper than aerial photography.

In forestry, aerial photography cannot substitute terrain survey, but it complements it. Aerial photographs could, for instance, form a photo archive of a region or be used as a basis for planning drainage of peatlands. In research, aerial stereo photography could become a new discipline.

The article has a German summary.

• Sarvas, E-mail: rs@mm.unknown

The annual fellings and sales of pulpwood from the State Forests of Finland comprised 4.0–4.6 million m³ in 1955–1959. In order to improve the accuracy of the methods used in estimating the pulpwood stocks marked for felling, a pilot survey of 18 marked stocks was carried out in 1959. The stock area, average plot volume, variation of the plot volumes, size and shape of the plot and the distribution of the trees by diameter classes as factors affecting the precision have been studied in this paper.

The greater the mean volume of a plot the more homogenous is the structure of the marked stock. The same number of plots gives a better relative precision for the south Finnish marked stock than for the north Finnish ones, which are heterogenous and less valuable. Stocks smaller than 50 ha can often be estimated more advantageously by the strip method or visually than by the plot method. The proper size of plot in Southern Finland is 0.02–0.03 ha. In Northern Finland the plots should be larger due to the heterogenous stocks, about 0.05 ha. The shape can be either circular or rectangular. The former may be more practical and reliable in the field. The minimum number of sample trees is considered to be about 200 per 100 sample plots 0.03 ha in size.

The PDF includes a summary in English.

• Kuusela, E-mail: kk@mm.unknown

The purpose of the investigation was to study the characteristics of the site and the growing stock and the effect of their variation on the precision of forest inventory. The total area of the forest tract is considered to be already known or it can be measured with surveying. The sub-areas or strata and the mean timber volume of each wooded stratum are estimated by sampling. Thus, the total volume of each stratum is the product of the estimates of the area and mean volume. Only line method of sampling the areas will be examined. Field material was measured in the inventory of the Finnish State Forests with the method used in the third National Forest Inventory. The circular plots and the sample trees were measured in the forests of Inari district. In this systematic line-plot method the distance between the lines was 5 km.

The results show that the total area should be broken down into suitable strata, such as the full-stocked productive forest land and regeneration areas with mother trees. The mean volume for each stratum is estimated with the plot method. An advanced estimation of the approximate mean volume and the coefficient of variation in the strata are needed for calculating the optimum allocation of plots.

If the volume calculation is done with the diameter as variable the variation of the plot volumes is decreased. If the local volume table is used and the site and stock characteristics differ from the characteristics of the volume table stock, a significant systematic error is possible. Planning of efficient and economical forest inventories requires data concerning site and stock variation. It should be calculated and published systematically by geographical region.

The PDF includes a summary in English.

• Kuusela, E-mail: kk@mm.unknown

The purpose of the investigation was to study the factors which determine the amount of the largest permanent allowable cut and to work out a method to estimate it. There is a need to have a ’short cut’ formula for rough preliminary estimates. The preliminary estimates will be checked by stock development forecasts. The largest allowable cut and its sustained basis are only guaranteed by a forecast through a period during which all the present tree stands have reached maturity and exploited.

Estimations of the largest permanent allowable cut are based on the data of the present and desirable growing stock. The present stock was a growing stock of Scots pine (Pinus sylvestris L.) dominated stands on Vaccinium type forests in Southern Finland. The connected Austrian formula is a simple way for preliminary estimation of the largest cut but its sustained basis must be checked by a stock development forecast.

In a stock development forecast the future increment and cut are calculated. For this purpose, the average site quality, tree species, age class and average volume in each class seem to be sufficient variables. The forecast is carried out within the limiting data of the present and desirable stock.

If there is an abundance of mature and over-mature stands, the largest permanent allowable cut is greater than the present increment, provided, however, that bulk of the cut is drawn by determined generation measures. Measured in solid cubic meters, the sustained cut from the Southern Finnish pine stock exceeds the present increment by 11%. With regard to the sustained saw timber production the cut can exceed the present increment by 5–7%.

The PDF includes a summary in English.

• Kuusela, E-mail: kk@mm.unknown

A strip survey was made to define the forest and peatland site class distribution and the condition of the forests in Savo and Karelia in central and eastern parts of Finland. According to the survey, 24% of the forested lands are peatlands. Fresh mineral soil sites (26%) were the most common mineral soil site type. Intermediately dry forest soil sites covered 22% of the area, forest sites with grass-herb vegetation 12,79%, rich grass-herb forest soil sites 3,16% and dry forest soil sites 9,59% of the forested area. The most common tree species were Scots pine (Pinus sylvestris L.), 39%, Betula sp., 26%, Norway spruce (Picea abies (L.) H. Karst.), 18%, and grey alder (Alnus incana (L.) Moench), 10% of the forest land. The article includes a review about the wood harvesting in the forests, and their present silvicultural state. According to the study, about 30% of the forested lands (not including peatlands) were unproductive; mostly mixed alder and birch stands of poor quality or open lands.

The PDF includes a summary in German.

• Multamäki, E-mail: sm@mm.unknown