BY BO EKLUND
SWEDEN, similarly to the two neighboring countries, Finland in the East and Norway in the West, is preeminently a land of forests. Of the total land area 410,600 km2 - some 231,800 km2 or 56 percent consists of forest land. Owing to Sweden's very considerable length from North to South - the distance between the northernmost and southernmost points is 1,574 km - and the land's northerly situation (between 55° 20' and 69° 04', northern latitude) and varying geological, climatic, and topographical conditions, the nature of the forests differs considerably in different parts of the country. Practically the whole country is dominated by conifer forests which either consist of unmixed stands of pine, Pinus silvestris, or spruce, Picea abies, or of mixed stands of these two trees with an intermixture of birch, Betula verrucosa and B. pubescens, which are the most commonly occurring broad-leaved trees. In the southern part of the country stands of rarer broad-leaved species, principally beech, Fagus silvatica, are also found.
Extensive forest exploitation in the past and the resulting legislation have had profound effects on the Swedish forests today. The exploitation of the natural forest resources - in many cases conserved for centuries - has proceeded without interruption for nearly a hundred years but is now reaching its conclusion: the last remnants of the primeval forests in northern Sweden, where exploitation began much earlier than in other parts of the country, have now been almost entirely cleared.
In order to ensure a supply of raw materials for Sweden's forest industries, it is essential for the nation to build up a productive forestry. Conversion from exploitation to a productive basis was initiated some decades back in many parts of the country, but much remains to be done before the productive capacity of our forest land and its growing stock can be utilized more effectively. The need for a deeper knowledge of the conditions of forest growth and of the results that may be anticipated from the conservation measures Sweden adopts must be regarded as an essential prerequisite.
Increased knowledge can only be gained, however, by extensive forestry research, the main purpose of which is to afford an efficient guide in all practical matters relating to production. Work in the numerous fields of forestry research is accompanied by difficulties, many of them connected with the long period of growth. Furthermore, present-day Swedish forestry is marked by a special characteristic, namely that the yield of wood is cut progressively as thinnings during the greater part of the life of the stand. Under conditions of growth prevailing in Sweden, a period of 80 to 100 years or more usually elapses between reforestation of a stand and its cutting; it is then possible to survey the total yield and judge the effect obtained from the application of a certain forestry program. On this account, forestry research, unlike agricultural research, has not thus far had the benefit of personal experience and observation in connection with the most suitable system of forestry to be followed under varying conditions.
Old, very slow-growing spruce stand of a type common in northern Sweden.
As far back end of the nineteenth century a project was formed to set up a central research body for forestry under state administration, providing for scientific handling of a series of important problems. After various proposals had been submitted and numerous discussions had taken place, the Forstliga Försöksanstalten, or as it shortly afterwards became known, Statens skogsförsöksanstalt (Swedish Institute of Experimental Forestry) was established in 1902. This institute was originally organized on very modest lines. It was soon recognized, however, that the requirements of the organization had been considerably underestimated, with the result that in 1912 state authorities voted funds for an appreciable extension of its activities and for the erection of a special institute building at the Experimentalfältet close to Stockholm, which was occupied in 1915.
The last few decades have been accompanied by important developments in Swedish forestry, especially more intensive forms of cultivation, and the need for forestry research has increased in step with these developments. The scope of the 1912 organization was soon found to be inadequate and a further extension became inevitable. Proposals for a new organization, based on a series of reports dealing with present and estimated future research requirements, were placed before the parliament in 1939 and were approved in principle. In consequence of world events the reorganization was not carried out until 1944. It resulted in increase in staff and material resources, the erection of a new institution building, and the rebuilding and extension of the older building. Further additions to the organization were made during 1945 and 1946. In conjunction with the reorganization the name was changed to Statens skogsforskningsinstitut (Forest Research Institute), which more adequately represents the nature of the Institute's activities.
The Forest Research Institute has two main tasks: 1) to determine the most suitable methods for the conservation of forests under different conditions, and 2) to keep running inventories of the country's available forest resources. These general headings cover a series of the most varied tasks, a number of which are associated with the basic forest research plan, while others relate to the research methods adopted. In order to meet the requirements, work is carried on by five divisions - dealing with Forestry, Statistics, Botany and Soils, Genetics, and Zoology - all of which are under the Director of the Institute, who bears a professor's title, and is also head of the Statistical Division. A general secretarial office is available for the whole Institute. The Institute is governered by a board which is common to the Skogshögskolan (Swedish College of Forestry) and the Forest Research Institute.
The director's chief duty is to co-ordinate and direct the work within the Institute and to maintain contact with other research institutes and with the practical side of forestry. For the management of the Statistical Division, which deals with forest surveys and cutting statistics, the director is represented by a special research leader, and for dealing with administrative and financial matters he is represented by a secretary who also officiates as secretary to the board.
A professor is in charge of each of the other five divisions, with one or more research workers and assistants under him. The head of a division and his Research leaders each have a special field of research allotted to them. In addition, trained forest rangers, laboratory assistants, calculators, etc., are attached to the different divisions. In the year 1947/48 the staff numbered 110. During the field-work season, from May to October, a large extra staff is employed. The annual budget for the Institute amounts to approximately 1¼ million Swedish crowns ($350,000 U.S.).
A great part of the work, as is common in forestry research, must be based on material obtained from observation and research in the field, which in the great majority of cases can be concentrated in permanent or temporary sample plots. The Forest Research Institute now has more than 900 permanent sample plots at its disposal and about 1,000 temporary plots, distributed over practically the entire country. The first permanent sample plots were laid out in 1902, so that it has been possible to keep them under observation and carry out regular surveys over a long period of years. In view of the new and, in some cases, epoch-making working systems based on modern analytical methods of a mathematical-statistical nature, it is probable, however, that future field research work will be confined to sample plots subjected to a single survey. In addition, the Forest Research Institute has under its control four experimental parks, two of which are in the North and one each in Central and South Sweden. The purpose of these experimental parks, which comprise a total area of 3,400 hectares of forest land, is partly to allow certain research work to be centered in a district for which a careful inventory and description has been prepared, and partly to permit forest management measures to be studied when applied on a large scale.
Sample plot in a North Swedish pine forest, about 85 years of age.
The foregoing gives a general idea of the Institute's organization and activities. To complete the picture, however, it is necessary to refer to the work of the different divisions.
The Forestry Division deals with research work relating to silviculture, forest mensuration, and forest technology. The chief task of the division consists in making practical deductions in connection with the main problems of silviculture. Its research work touches upon all phases of the long production period between the reforestation of the stand and its final cutting. Thus it covers all problems associated with forest management during the long period of growth - when the first thinning should be undertaken, the frequency and extent of thinning, and the most suitable time and method of cutting mature trees. It also deals with the best methods for producing new forests to replace the old ones. The work is therefore directed as far as possible towards discovering the most suitable methods of forest management to adopt in order to achieve the best possible economic yields. Widely varying problems are encountered in actual management and reforestation, and the work takes the form of both production research and reforestation Research
Investigations have been carried on for a long time by international forestry research bodies with the object of determining the stand development and yield on varying site-class qualities when employing a single method of thinning. The material investigated has comprised permanent sample plots which have been treated for long periods on similar principles insofar as the methods and amount of thinning were concerned. The aim of the work was to determine the effect of the cutting program adopted on the progress of development and yield, by simple graphic comparisons of the estimated yield results from sample plots, representing similar starting points with respect to habitat factors and stand structure. Production Research by this method must be spread over a very long time, since it must include the greater part of the stand's period of growth.
In order that the demands of practical forestry for scientific guidance in the efficient management of a stand could be met within a reasonable time, it became necessary to alter production research for more rapid results. Research work of this kind has consequently been directed toward a closer investigation of the stand's manner of growth under varying natural conditions and different methods of treatment. The main purpose of the work is to produce statistical data from which general deductions concerning the observed growth may be drawn, based on the observations carried out over short periods of development - representing the growth between two thinnings, or about five years. In this way it is possible to estimate the probable future growth, i.e., to predict the development of forest stands representing widely varying initial conditions of stand locality and cutting conditions. Statistical analysis may be regarded as an experimental branch of research; in order to produce statistical functions that can be satisfactorily applied, the ordinary tasks of research must be approached from new starting points, a process that usually entails far-reaching calculations. On this account it has been necessary to organize a large calculating department, which is provided with the most up-to-date equipment, including machines for sorting and adding punch-cards.
Starting from the functions of growth, production tables are prepared which show the development and yield of a stand, with respect to quantity and value, based on varying combinations of assumptions concerning the structure of the stand and the cutting program adopted. By this means it is possible to make an objective comparison of the results obtained with various forms of stand management, starting from identical initial stand conditions, which is never possible in direct practical research. On the basis of such comparisons, conclusions can be reached as to which form of silviculture will prove most advantageous in each particular instance.
It was necessary to base the production analyses carried out hitherto on the Institute's permanent experimental plots. These were originally laid out and subsequently managed with a view to practical research work over long periods and they were not intended from the outset for statistical work along modern lines. The work has therefore been accompanied by difficulties which are not usually inherent in the statistical methods as such. On this account the laying out of a large number of sample plots over the whole country has been in progress for some years. It is intended to lay out from 4,000 to 5,000 temporary plots, from which comprehensive data can be collected by a single survey.
The growth in diameter of trees is examined by boring and measuring the width of the annual rings; measurement is done by special machines. Apart from the time gain, which is of decisive importance, there are other advantages to this method of investigation. It is possible to determine the growth in diameter far more accurately than by repeated diameter measurements on permanent plots. In view of the fact that the sample plots are now of a temporary character, representative sample trees can be cut for a comprehensive series of measurements and observations to determine the quantity and quality of yield.
The new production research methods relating to pine, spruce, and birch forests, as well as mixed stands of conifers and hardwood, have a further purpose, however, apart from the possibility of predicting production. By the provision of a large number of sample plots on which growth can accurately determined and described in detail as regards the nature of the site and the individual trees, the possibility is afforded of obtaining a deeper insight into the conditions of growth. To this end, careful analyses are made of the ground vegetation on the sample plots and samples of the humus covering and mineral deposits are collected for investigations into the condition of the soil. In addition, samples are taken of the needles in the crowns for chemical analysis. Those characters of the felled trees are observed and described which are believed to be typical of different genotypes of trees. By simultaneously noting both heredity and environment, it should be possible in the statistical work to separate the influence of milieu and race, a point of fundamental significance for the improved culture of forest trees.
In consequence of the great extent of the field work and the lengthy nature of the statistical work, some considerable time must necessarily elapse before the enormous mass of material accumulated from production research can be utilized to advantage. For the immediate future Sweden will have to rely on the information and experience gained from observations made on the Forest Research Institute's permanent sample plots for information relating to the production conditions of a stand under various forms of management.
In connection with the forest production research, experiments on forest products are also being carried out by the forestry division, which of course relate primarily to the wood and its products. Investigations are in progress to ascertain what influence tree race, age, site, method of establishment, and system of management exercise on the yield and quality of sulphate pulp produced from pine wood and sulphite pulp from spruce. These investigations are carried out in collaboration with the central laboratory of the cellulose industry. In connection with the Swedish Wood Technology Institute, which undertakes the actual research, extensive investigations are planned on the technical properties of timber, such as strength, swelling, shrinking, etc., and on the extent to which these properties are due to special characteristics of the site, the stand, and the species.
Rapid clearing of the old natural forests in northern Sweden, which in many cases included fine-ringed timber free from knots, has brought about a pronounced shortage of high-grade timber for the sawmill and plywood industry. To compensate for the shortage of knotless timber, prunings of trees suitable for the purpose have been carried out in stands of spruce and birch during the last few decades. The influence of pruning on the quality of the timber and the state of health of the pruned tree is being studied.
The transition from exploitation to productive forestry has been accompanied by a lack of balance in age groups in Swedish forests. Particularly in the north of Sweden, where the natural conditions for regeneration are frequently very inferior to those in other parts of the country, there is a marked disparity between forest land with satisfactory reforestation and cleared forest land or land on which regeneration is unsatisfactory. In other parts of the country also there is a great need for the reforestation of cleared areas and land on which the quantity of timber is unsatisfactory. Thus, side by side with production research, reforestation occupies a prominent place in the research program of the Forestry Division. One of the problems in this field is to ascertain under what conditions natural reforestation can be brought about, and the possibilities of improving reforestation results by the more rational clearing of cutting areas, preparation of the ground, and burning over cleared areas.
An inventory of the northern Swedish forest resources was made during the years 1939-43, and the serious nature of the reforestation problem in this part of the country was confirmed by figures. The unduly optimistic view hitherto held concerning the possibilities of restoring great parts of the forest land in this district by natural means had to be revised; actually, new forests could only be produced over wide areas by sowing or planting. Reforestation research is now being undertaken to ascertain the biological possibilities for these two forms of cultivation and the means of improving forest cultivation. Considerable attention is devoted to the development of the forest cultivation methods themselves, with a view to obtaining higher efficiency and reduced costs. According to experiments made, it appears that the cost of forest cultivation can be appreciably reduced by preparing the ground with special caterpillar tractors.
Forest technological research represents an entirely new branch of work, which, because of limited resources, had been restricted to working studies in silviculture and allied questions. In order to render forestry more profitable and thus raise the standard of living for Swedish woodsmen, who, as far as wages are concerned, are the worst situated of all occupational groups under present-day Swedish social conditions, an intensified investigation of the theory of work is an essential preliminary. For this reason an appreciable increase in the research resources of the Institute is highly desirable.
The Forestry Division's work program also includes research in forest mensuration. Thus, objective methods have been worked out in recent years for computing the volume of standing trees and their distribution into different assortments. A number of these investigations are carried out in collaboration with the Statistics Division, in order to place improved survey methods at the disposal of this division.
The main work of the Statistical Division is to carry out repeated surveys of Swedish forest resources for the purpose of estimating their extent and condition and recording any changes that occur. Such surveys, undertaken at regular intervals (approximately 15 years) are of vital importance to Swedish forestry and the woodworking industries. They give a reliable idea of the available raw material and the cutting policy can be adapted accordingly.
The importance of obtaining a clear general picture of Swedish forest resources was recognized at the beginning of the twentieth century, and to this end a trial survey was started in 1911 in Varmland, a central Swedish province. The method of survey then adopted - a sample investigation in the form of a regular line survey - has since been used, although in a more developed and improved form, both for the two Swedish National Forest surveys (the first carried out in 1923-29, the second started in 1938 and still in progress), and also for the Finnish and Norwegian national surveys. In applying the line-survey method, various observations and estimations are made along strips of equal width, which are laid out on the ground by the aid of the compass at the same distance from each other. The surveying crew consists of 7 to 10 members. The different classifications of the area, such as distribution into land-utilization classes, into owner categories, site- and age-classes, etc., are based on the measured lengths of the different classes within a 10 or 20 meter-wide strip along the survey line. The direction of the latter is indicated by a rope, approximately 80 meters in length, which the compass-man drags along behind him. The growing stock was previously computed by counting the trees within a strip 10 meters wide, along the line, but it is now estimated on circular sample plots, five or six of which are laid out within every 2 kilometers, this distance being the survey unit. Beside counting the trees, requisite observations are also made on these sample plots, such as measurements of sample trees. On these observations are based the factors for computing the volume, increment, etc.
Reproduction front in a pine forest, Pinus sylvestris, (Middle Sweden).
Both the area of the forest land and the growing stock are registered in detail during the survey. The forests are classified according to quality, age classes, degree of density, owner categories, etc. The different owner categories registered are state forests, other public forests (i.e. ecclesiastical forests, community forests, etc.), company forests, and private forests. In southern and central Sweden the last group is further divided into holdings above and below 200 hectares of wooded area. By means of this special classification, it is possible to obtain pertinent data on forest resources and their condition among the different groups of owners.
The survey being a sample investigation, its reliability can be determined with the aid of the calculus of probability. The reliability has a certain relationship to the distance between the survey lines, the size of the sample plots, and the distance between them. A reduction of these distances would naturally increase the accuracy of the result But it is necessary to balance greater accuracy with the increased cost of the survey. In estimating growing stock, the aim has been to obtain approximately the same degree of accuracy (a standard error of 1.5 to 2.0 percent) in the different provinces. In northern Sweden the survey lines were laid out in a direction from southwest to northeast, the distance between the lines varying from 6 2/3 to 10 kilometers. In southern Sweden a crossline system is employed, one set of lines passing from north to south and another from east to west, the distance between the lines varying in the first case from 2 to 10 kilometers, and in the second from 1 to 5 kilometers.
Virgin spruce forest, Picea excelsa (South Sweden).
Another task of the Statistical Division is to collect data on the annual cut for the entire country. In close collaboration with the Forestry Division, calculations are also made concerning the estimated future quantities of timber and pulpwood that can be cut in the Swedish forests on a sustained-yield basis under various management conditions. A number of such calculations have recently been published for northern Sweden. These show very clearly that a felling policy more restricted than hitherto must be adopted in order to stop the current decrease of raw materials for the large Swedish forest industries.
The numerous and varying registrations collected by the Statistical Division also provide a valuable source of information for special investigations carried out on behalf of different institutions and public authorities.
BOTANY AND SOILS DIVISION
Work in this division is devoted to research relating to geobotany, soil biology, mycology and plant physiology, and their related problems, stress naturally being laid on research work with a direct bearing on forest problems. The main task of the division is to investigate the complicated processes that take place in the soil and in the trees, which together constitute the biological background for the productive and regenerative conditions for forest trees. The results of causal research work of this kind can be expected to yield valuable information on a variety of practical problems in the Forestry Division's field.
The growth of a tree is dependent to a very great extent upon the conditions in the ecological habitat of which the tree forms an integral part. This habitat is characterized not only by the original composition of the place of growth as such, but also by the local climate and the competition amongst individual trees. Such competition is very largely three-dimensional. It makes itself felt both in the crown of the tree, where the photosynthesis of the nutriment drawn from the air and through the roots takes place, and in the soil, where water and nutriment are absorbed and where a series of chemical, physical, and biochemical processes take place which, directly or indirectly, are of vital importance to the tree's growth functions. For these reasons it is extremely important to ascertain not only the organic requirements of individual forest trees and their initial characteristics but also the organic processes and collective life in forest land as well as the various types of growth in forests, the requirements of stand localities, and their reaction to various forms of treatment. The supply of latent nitrogen in forest soil, which is a vital production factor, thus has no direct connection with the original condition of the soil but is mainly a result of the manner in which the nitrogen has been conserved in the place of growth.
This many-sized combination of problems must be approached primarily by means of experimental Research methods, which implies that the original conditions of habitat must be changed by the adoption of various measures such as thinning, watering, fertilizing, etc. Such measures bring about biological reactions which reflect changes in the standard of nutriment and likewise react upon the structure of the ground vegetation. Ecological experiments of this kind are in progress in different parts of the country and have already shown clearly that the growth of forest trees is at times restricted by lack of nutriment in the soil. On ordinary firm soil this is found to be specially due to a lack of nitrogen, while on sterile peat moor it can be attributed to a lack of mineral salts.
In the geobotanical field investigations are carried out in connection with plant associations in the forests and particularly with respect to the different types of such associations (forest types) and the character of the stand locality. In Swedish forestry the type of forest is a widely used simple expedient for classifying forest land from the point of view of management. For this purpose the type of forest is determined primarily from the nature and composition of the ground vegetation and the frequency of its occurrence, and may be regarded as an indication of the manner in which a stand of trees should be treated. In geobotanical research the aim is to test and define as closely as possible the value of the different forest types. Since it is scarcely possible in practical forestry to base the measures to be taken in forest management on detailed analyses of the soil, a well-defined schedule of forest types, with the resulting indications for the management of stands, offers the most practical form of procedure in the present state of knowledge. It likewise constitutes part of the Research work to ascertain what changes are caused in the forest types by cutting and other measures.
Soil biology research investigates processes of a biological nature, of importance to the life functions of forest trees, that take place in the soil. The soil is one of the sources of nutriment for the tree and its food supply exercises a decisive influence on its growth. Information can also be acquired concerning the part played by the richness of nutriment in forest production, by means of ecological experiments. Thus, it has been found that the production in old spruce forests of a type very common in northern Sweden could be approximately trebled by adding fertilizer.
In order to increase the supply of nutriment in the soil the only course available in practical forestry is to attempt to improve the relations between the supply and demand for nutritive substances by appropriate cutting, and to bring about conditions in the soil that are most favorable to the organic processes. The task of soil biology is, therefore, to accumulate information on the organisms in the soil, their influence and organic requirements, their reaction with one another and on the roots of the tree, etc.
Research has hitherto been directed primarily towards ascertaining how the tree's nutriment is released from the store concentrated in the soil, by means of thinning and the killing of bilberry bushes or heather with chlorate or in some other manner. The effects of fertilizing in this way are now generally known in principle. Taking the long view, however, it is equally important to determine the rate and the extent to which the nutriment in the soil is renewed, since the possibility of carrying on permanent forestry without exhausting the nutritive qualities of the soil is dependent upon the answer to this question. In this respect the biology of forest soil presents a practically unexplored field of research.
In the mycological branch research is done on the fungus diseases of living trees as well as on destructive fungi and the damage they cause to wood products. The task of chief importance is to discover means and methods to prevent or counteract the damage done by these fungi. Extensive investigations are in progress in connection with Phacidium blight, Phacidium infestans, a form of fungus which, particularly in the higher latitudes or northern Sweden, gives rise to considerable damage in young pine stands. Similarly, a profound study is being made of the various diseases of a mycological origin which cause havoc in new plantations. Pine blister rust, Cronatium asclepiadeum, occurs in all parts of Sweden as a harmful influence in pine forests. Spruce are attacked to a much greater extent than pines by rot fungus of which heartrot or rootrot, Polyporus annosus, sometimes causes serious damage in pine forests. C. asclepiadeum and the various other forms of fungi which produce decay in pine trees are being comprehensively investigated.
Material amounting to millions of crowns in value is ruined annually in Sweden through forest products, the chief of which are timber and wood pulp, being attacked by fungus diseases during the period of transport to the woodworking industries and storage at the point of use. Intense research work is in progress, however, to discover prophylactic or direct methods for counteracting this damage. Since it is suspected that fungus infections are transmitted by insects in some instances, as for example in the case of discoloring, the investigations are being conducted in collaboration with the zoological division.
In recent years antibiotic countermeasures have rightly attracted some attention in the fight against diseases caused by microorganisms. In forest trees, too, substances with an antibiotic effect are produced which possess the character of natural root fungi poisons. Two phenolic substances have been isolated from the heartwood of pine which exercise such poisoning effects. In this field of research, which opens up unsuspected aspects in the fight against wood-destructive microorganisms, investigations are carried on in collaboration with the Royal Technical High School's Institution for Organic Chemistry.
For many years past genetic research has been carried out on a certain scale by the Forest Research Institute. In amplification of the reorganization undertaken in 1944, genetic research was transferred to an independent division in 1946, in order to carry on the work in a far more intensive way than was hitherto possible. Its primary purpose is to improve the culture of forest trees, preferably by selective methods.
Attention has already been drawn to the feet that very extensive forest cultivation must be undertaken to ensure the future of wood production in Sweden. According to a survey made by the Forest Research Institute, a forest area of some 100,000 hectares must be planted annually with approximately 60 tons of seed. The heavy costs of restoration, the greater part of which are due to manual work, make it highly desirable that genetically sound seed be employed. Only by this means can satisfactory cultivation be assured and a firm foundation laid for a future production of high quality and quantity on the stand cultivated. In selecting the seed for forest restoration work, and considering the possibilities of transplanting pine and spruce seed from one district to another, it is anticipated that the provenance research carried out by the Institute will offer valuable guidance. As already mentioned, the difficulties of reforestation are particularly marked in northern Sweden. This is due, among other things, to the feet that good seed years occur in this district at longer intervals than in the southern and central parts of the country. It is a matter of importance, therefore, to be able to determine in a horizontal and vertical direction the limits within which forest seed may be planted without risking the result. Provenance research also seeks to ascertain whether, by planting seed between districts with different climatic conditions, it is possible to improve the production in comparison with seed produced in the locality itself.
The possibilities of increasing forest production quantitatively have aroused great interest in Swedish forestry circles. During recent decades great efforts have also been made to improve the quality of production and therefore the value of the output. With this end in view, trees of the poorest quality have been cut down systemically during thinning, and as far as possible those trees have been left standing which, judging by their external appearance, have the most valuable properties of quality and growth. In order to obtain seed of good quality the systematic plan has been followed of allowing the finest trees to remain as seed trees when clearing a stand. When planting out pine or spruce seedlings, the practice has been adopted in recent years of selecting the fastest-growing and qualitatively best plants from the available material and rejecting the inferior plants.
By combining genetic research with the more practical forms of improved culture, it is believed that rapid and appreciable gains will become available. In this connection, research work is being directed towards an inventory of Swedish forests, more particularly with respect to the value of different types of stands and trees,- and their properties are being carefully studied. The extensive material accumulated by the Forestry Division from closely investigated and described sample plots will provide a valuable starting point.
The subsequent task of this research work will be to find an answer to the question: What actual influence does the genetic structure of a forest tree exercise upon the productive conditions of the stand? The properties of the tree can always be traced back to the influences of both heredity and environment. As previously mentioned, the mathematical-statistical work carried out with the observation data obtained from the Institute's sample plots, in conjunction with production investigations, affords certain possibilities of separating these influences from one another. It may be taken as a reasonable working hypothesis that the properties of a given distinct type of tree, which cannot primarily be attributed to any known kind of environment, is the result of the genetic constitution. Future research must specially consider whether the properties of parent trees of various types are inherited by the offspring. Investigations are being planned in collaboration with the Institute's entomological and mycological workers to ascertain whether any races or types of trees exist, or can be produced by crossing, which are capable of resisting parasitic fungi and injurious insects.
Owing to their great variety of species and profusion of numbers, insects constitute the major element among forest fauna. For this reason and because insects play a far more important economic role than other forms of animal life, the Zoological Division is mainly engaged on problems associated with the occurrence of and damage done by these insects.
The nature of the damage insects cause in the forest varies considerably; certain species attack and consume foliage, while others burrow under the bark or into the wood. The damage done sometimes causes the death of the tree or it may result in a reduction of its vital functions, with a consequent decrease in growth or the production of defective qualities.
Other insects attack sickly trees, either fallen or standing; such types, from man's point of view, are relatively harmless under normal conditions. In the event of wholesale multiplication, however, as after storms, forest fires, etc., they may constitute a serious menace and attack and kill healthy trees.
Swedish insect fauna include relatively few species that are helpful from the forester's point of view. Among these may be reckoned parasitic and predatory insects which attack the injurious insects themselves. Insects that accelerate the decomposition of the soil cover are likewise helpful to forestry.
One of the most important tasks of the Zoological Division is to add to our knowledge relating to the biology of injurious insects and to work out means of controlling them. Greatest attention has been devoted in the past to our most troublesome species of bark-beetles, Blastophagus piniperda and Ips typographus. As a result of this work information of value to practical forestry can be obtained on suitable methods of control. An intimate knowledge of the biology of injurious insects is important because it provides data on the stage of development in which a certain species of insect offers the least resistance and can therefore be combated most successfully. Thus it is possible in many instances to reduce or eliminate the damage caused by a given type of insect without resort to expensive measures.
The division also plans suitable methods for estimating the frequency of occurrence of injurious insects and the amount of the damage they cause, as a basis for judging the extent of the control measures required.
The relation between certain injurious insects and fungi likewise forms a subject of investigation in collaboration with the Institute's mycological experts. Here attention mainly directed towards ascertaining the connection between discoloration of wood caused by blue-staining fungi and insects that attack felled timber.
The program likewise includes investigations relating to animal life in the forests, the purpose of which is to increase our knowledge of the insect fauna occurring in the soil and the part they play in the processes taking place in the soil as well as in reforestation.
In recent years the contact poison DDT has been produced which exercises a nerve-paralyzing effect on insects and which, judging by results, offers a valuable means of combating injurious insects. The Zoo logical Division has been investigating the possibilities of controlling forest insects by dusting DDT powder from airplanes or helicopters, with very promising results.
This is a brief account of the Forest Research Institute - the official body for Swedish forest research - its organization and more important work. The solution of the problems concerned call for close cooperation among the divisions and subsections of the Institute - between basic research and applied research - and also in many cases with other scientific institutions and the practical side of forestry. The main object of the Forest Research Institute's activities is to afford guidance to the forester in the management of our great natural resource, the Swedish forests.
Dusting severely insect-damaged forest with DDT powder from a helicopter.
Photos accompanying this article were furnished by courtesy of the Forest Research Institute of Sweden.
