Articles containing the keyword 'forest mensuration'

Cut-off importance sampling (CIS) is introduced as a means of sampling individual trees for the purpose of estimating bole volume. The novel feature of this variant of importance sampling is the establishment on the bole of a cut-off height, H_C, above which sampling is precluded. An estimator of bole volume between predetermined heights H_L and H_U > H_C is proposed, and its design-based bias and mean square error are derived. In an application of CIS as the second stage of a two-stage sample to estimate aggregate bole volume, the gain in precision realized from CIS more than offset its bias when compared to the precision of importance sampling when H_C = H_U.

• Robinson, E-mail: ar@mm.unknown
• Gregoire, E-mail: tg@mm.unknown
• Valentine, E-mail: hv@mm.unknown

This paper deals with the testing of dynamic stratification for estimating stand level forest characteristics (basal areas, mean diameter, mean height and mean age) for a 117 ha study areas in Finland. The results do not show possibilities to achieve more accurate estimates using only Landsat TM principal components as auxiliary data opposed to static stratification. It was found that in dynamic stratification non-measured observations should be assigned the mean characteristics of the measured observations that belong to the same cube (class) instead of stratification variable classes until a certain limit. If only one principal component is used the number of classes has, however, little influence. Low field values are overestimated and high values underestimated.

The only successful results were obtained using two variables of different origin – the qualitative development stage class and the quantitative 1st principal component. The lowest root mean square error in estimating basal area was 6.40 m²/ha, mean diameter 3.34 cm, mean height 2.65 m and mean age 14.06 years. This increase of stratification accuracy is mainly resulted by the use of development stage class as an auxiliary variable.

• Mozgeris, E-mail: gm@mm.unknown

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

The choice of sampling method is of prime importance when seeking relevant information about the height distribution and spatial arrangement of seedlings in the regeneration surveys. It is suggested that the size of sampling plots should depend on the height of the seedlings. Tall seedlings should be sampled from a larger area than short ones since tall seedlings are more important for the future development of the stand. We suggest principles for a technical development task to construct a device which is easy to use in practical regeneration surveys and by which sampling can be made proportional to plant height or any desired function of height.

The PDF includes a summary in Finnish.

• Lappi, E-mail: jl@mm.unknown
• Kotisaari, E-mail: ak@mm.unknown
• Smolander, E-mail: hs@mm.unknown

This paper presents the principles of a unified data processing system suitable for derivation of the most variables of interest in forest mensuration. The precedence (succedence) relations between the tree and forest stand variables are analysed and a block-wise simultaneous recursive multi-equation model is suggested to describe these relations. Regression analysis is used in the estimation of the model parameters and Taylor’s series and Monte Carlo simulation are available in the derivation of the unbiased results.

The PDF includes a summary in Finnish.

• Kilkki, E-mail: pk@mm.unknown

The general requirements for forest information required in forest management include the availability of quantitative data concerning forest areas and timber volume, data describing that structure and quality of the forest by classes, data dealing with the forest dynamics such as increment and mortality, stand-wise data tied to on-the-ground locations, and the timelines of all this information.

A review of the present inventory systems reveals variations in the information used to manage forests. In many cases, there appears to be an inadequacy of information. There may be no inventory system, or sampling may concern only overall features of the forest. The general trend has been towards a more common use of delineation of stands and the estimation of stands characteristics. In European countries, survey techniques have been improved by, for instance, trying to avoid subjective features in stand-wise assessments and through the use of index sub-compartments which are remeasure. In North America, a new approach was recently introduced to generate stand tables which seems to have significant inventory capabilities. In some cases, the advanced inventory systems may simultaneously employ three kinds of inventories.

In designing an inventory and management information system experiences gained elsewhere should be utilized with studies of sampling methods, remote sensing techniques, new instrumentation and computer services. Improved decision making makes it possible to introduce cheaper methods for periodic inventories. The information system should be only as elaborate as is required to do the job. The costs of acquisition of inventory information correlates with a degree of sophistication of the system, but rarely exceeds one percent of the stumpage of the timber cut. Also, the increase in wood production more than compensates the costs of planning on the basis of inventories.

The PDF includes a summary in Finnish.

• Nyyssönen, E-mail: an@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

After the Second World War Finnish Forest Service was faced with large e-mapping and timber surveying project in Northern Finland. The funds for mapping were very limited. In order to re-map the large areas, the only way was to look for alternative methods for the ground methods. The photogrammetric equipment of Finnish Army was made available to the civil service. Consequently, since 1947 several forest mapping projects were carried out in co-operation between the Forest Service and the Army Topographic Service.

When more funds were coming available for the project, new instruments were acquired. The article describes the present mapping procedure and suggests alternative ways in procedure and utilization of new equipment. It concludes that if the forest area under modern timber management plans is several million acres, the ideal implemental framework for mapping and timber surveying unit in Finland should be the following: Radial Secator RS I and slotted templates for the radial line plot, Stereotope Plotter for drafting general maps, the old Delft Scanning Stereoscope for photo interpretation, and Aero-Sketchmaster for transport of the photo details.

• 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

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

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

Silva Fennica Issue 39 includes presentations held in professional development courses in 1935 that were arranged for foresters working in public administration. 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 forest inventory methods.

• Ilvessalo, E-mail: yi@mm.unknown

The article is a lecture given by A.K. Cajander in the International Congress of Plant Science. The lecture describes results of Finnish forest research that might be regarded significant also for North America. Because of similarities in nature and forest management, forest research may use similar methods in both areas.

For instance, line plot survey in the form used in Finland could well be applied in North America. In Finland, lines were drawn at 26 kilometer intervals. Visual estimates about, for instance, species, tree growth and productivity class, were made along the lines and sample plots were taken every other kilometer. To gain full advantage of the method, a productivity classification and yield tables are needed. When these are known, it is possible to find out how to increase the productivity of forests with suitable tree species and proper forest management. This kind of inventory of forest resources and the state of forests provides reliable information for forest policy. Another important issue for forest research is forest management, which requires understanding on their biology. At the same time, research must provide methods for practical forestry.

A summary in Finnish is included in the PDF.

• Cajander, E-mail: ac@mm.unknown

Line plot survey has proven the best method to assess forest resources in the Northern countries on a country level; it is cost effective and gives reliable results. The accuracy of the survey depends on, however, how close the lines are set. To get homogenous statistics of an entire country, the survey should not span over too long a period. Thus, the distance between the lines should be chosen wide enough to give accurate results quickly for the whole country, while accepting slightly less exact results for its smaller districts.

If line survey is performed on large areas, it is not possible to count and measure trees, measure the tree growth. etc. along the whole length of the line because of its costs. Therefore, more precise measurements are limited to sample plots, which are spaced evenly along the lines. Between the sample plots, the volume and growth of each stand touching the line are estimated visually. These visual estimates have often systematic faultiness, which can be eliminated with correlation calculations. Visual observations gather information, for instance, about land owner, soil type, land-use class, forest site type, tree species and age class of the stand, density, wood volume ja annual growth per hectare, and the current silvicultural state of the stand. With help of this kind of information it is possible to get sufficient statistics about the forest resources of a country.

A summary in Finnish is included in the PDF.

• Ilvessalo, E-mail: yi@mm.unknown

The article highlights the need to classify the forest sites in objective and exact classes. This is important both from a practical and a scientific point of view as well as from a silvicultural point of view, for the forest management varíes for each tree species, and according to the site, even if the species remains the same. It is evident that the same classification of sites according to quality ought to be applicable to silviculture, forest mensuration and statistics. In Finland, a forest site type rating has been created for this purpose.

The PDF includes a summary in Finnish.

• Cajander, E-mail: ac@mm.unknown

The aim of this investigation is to study, for north European conditions, some overall standards of accuracy attainable in the estimation in a number of forest characteristics from aerial photographs. Field data was acquired in three areas, comprising whole stands, fixed and variable size sample plots and sections of survey strips.  

The results show that land use classes could be estimated to a rather high degree of precision from aerial photographs. The accuracy of determination of the main tree species (Scots pine, Norway spruce and deciduous trees) was more moderate; three quarters of all stands were interpreted correctly from the present photographs. The estimate of pure stands was noticeable better than those for mixed stands. In general, the agreement between treatment class stratification in the field and from aerial photographs was poor, as only one-third of all cases the class was same. The dominant height was estimated with relative lack of bias for small stands, but systematic underestimation of nearly 2 m existed for high stands.  

The emphasis in this investigation was laid on determination of the volume of growing stock. Stand volumes in the small and medium volume classes were overestimated, against clear under-estimate for high volume stands. The standard error of difference, including bias, was ±43 both in m3 and as a percentage. 

The variance data available provide a basis for the conclusion that under some conditions photo stratification within the forest land seems to improve the efficiency of volume estimation, whereas in some other cases the stratification is hardly an economic proposition. Alternative computations made from the data of an experimental survey indicated the likelihood that no gain was deprived from the use of aerial photographs for volume class estimation. 

The PDF includes a summary in Finnish.

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

This article is a review of Finnish forest research in the fields of forest mensuration and management during the previous 50 years. Of the studies special attention deserves the development, structure and growth of growing stock and forest survey. The development during the past half century has led to the differentiation of forest mensuration into a few independent fields of knowledge. Fields closely connected with forest mensuration are photogrammetry and statistical methods.

The article is published in Finnish in separate PDF Acta Forestalia Fennica vol 70 no 5.

• Nyyssönen, E-mail: an@mm.unknown

This article is a review of Finnish forest research in the fields of forest mensuration and management during the previous 50 years. Of the studies special attention deserves the development, structure and growth of growing stock and forest survey. The development during the past half century has led to the differentiation of forest mensuration into a few independent fields of knowledge. Fields closely connected with forest mensuration are photogrammetry and statistical methods.

The article is published in English in separate PDF Acta Forestalia Fennica vol 70 no 6.

• Nyyssönen, E-mail: an@mm.unknown

The article is a review of forest research carried out in Finland. The article includes a short review of the origins of forest research in the country and the research institutions in the country. It describes the main studies in different fields of forest research, divided on biological and silvicultural research, forest mensuration and forest policy research, and research on forest utilization.  English translation of the article was published at the same time with an Finnish article. A need for an English summary of the forest research was realized, because the publications have mainly been written in Finnish or German.

• Ilvessalo, E-mail: li@mm.unknown

The article is a review of forest research carried out in Finland. The article includes a short review of the origins of forest research in the country and the research institutions in the country. It describes the main studies in different fields of forest research, divided on biological and silvicultural research, forest mensuration and forest policy research, and research on forest utilization. An English translation of the article was published at the same time. A need for an English summary of the forest research was realized, because the publications have mainly been written in Finnish or German.

• Ilvessalo, E-mail: li@mm.unknown

The article describes a method to prepare growth and yield tables for forests in Northern Finland, which differ markedly from forests in the southern part of the land. They are mostly uneven-aged, and there are little forests that belong to separate age-classes. The forests are predominantly old. The most common age-class in the old forest’s group is 150-160 years. Also, the lands are poorer than in Southern Finland. Because the variation of the poorer sites is larger than in better sites, the number of sample plots needed to prepare the growth and yield tables has to be larger than in Southern Finland, where the lands are better. The yield tables cannot be prepared for all the numerous forest site types of Northern Finland. The number of age-classes has to be relatively low. In consequence, the growth and yield tables will not be as accurate as those made for the better forest site types in Southern Finland.

• Lakari, E-mail: ol@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

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

Two methods of pre-harvest inventory were designed and tested on three cutting sites containing a total of 197,500 m³ of wood. These sites were located on flat-ground boreal forest in north-western Quebec, Canada. Both methods studied involved scaling of trees harvested to clear the road path one year (or more) prior to harvest of adjacent cutblocks.

The first method (ROAD) considers the total road right-of-way volume divided by the total road area cleared. The resulting volume per hectare is then multiplied by the total cut-block area scheduled for harvest during the following year to obtain the total estimated cutting volume. The second method (STRATIFIED) also involves scaling of trees cleared from the road. A volume per hectare is calculated for each stretch of road that crosses a single forest stand. This volume per hectare is then multiplied by the remaining area of the same forest stand scheduled for harvest one year later. The sum of all resulting estimated volumes per stand gives the total estimated cutting-volume for all cut-blocks adjacent to the studied road. A third method (MNR) represent the actual existing technique for estimating cutting volume in the province of Quebec. It involves summing the cut volume for all forest stands. The cut volume is estimated by multiplying the area of each stand by its estimated volume per hectare obtained from standard stock tables.

When the resulting total estimated volume per cut-block for all three methods was compared with the actual measured cut-block volume (MEASURED), the analysis showed that MNR volume estimate was 30% higher than MEASURED. However, no significant difference from MEASURED was observed for volume estimates for ROAD and STRATIFIED methods, which respectively estimated cutting volumes 19% and 5% lower than MEASURED.

• Morasse, E-mail: jm@mm.unknown

• Pulkkinen, E-mail: minna.pulkkinen@iki.fi