Articles by Leo Heikurainen

This is the latest report in a series of publications from an on-going investigation which is concerned with the influence of different fertilization treatments and ditch spacings on the growth of Scots pine (Pinus sylvestris L.) seedlings and transplants growing on nutrient drained poor bogs in different parts of Finland. This paper concentrates on duration of the growth response to NPK-fertilization on the experimental plots. The experiment was established and the treatments performed in 1965–66.

The results show that climate, expressed as effective temperature sum (dd°C, threshold +5°C) has a clear influence on the duration of the fertilization effect. In Southern Finland (>1,200 dd°C), the duration was at least 15 years. In Central Finland (1,200–1,000 dd°C), it appears to be almost 10 years, and in Northern Finland (<1,000 dd°C), slightly shorter. The amount of fertilizer applied clearly influenced the duration of the fertilization effect. The dosage of 500 kg/ha (N 14, P 7.8, K 8.3 per cent) had, on average, a shorter duration than the greater dosages of 1,000 and 1,500 kg/ha. However, there was no clear difference between the latter two dosages.

The PDF includes a summary in Finnish.

• Heikurainen, E-mail: lh@mm.unknown
• Laine, E-mail: jl@mm.unknown

Young Norway spruce (Picea abies (L.) H. Karst.) are susceptible to early summer frost damage. Birch (Betula pubescens Ehrh.) naturally colonize rich or fairly rich drained peatlands after clear cutting, and can provide protection for developing seedlings. The report describes the development of spruce stands after various types of handing of the birch nurse crops.

Different proportions of birch and spruces did not have any influence on the spruce stand production. In cases where the nurse crop stand is removed when the spruce stand age was 20 years and height 4 m the spruce suffered badly but recovered with time, reaching the spruce stand growing under a nurse stand within the next 20 years. The height growth of spruce depends on the density of the nurse stand, especially on fertile sites. The development of diameter growth also depends on the density of the nurse trees. Removal of the nurse stand in spruce stands on the sites concerned should be done when the spruce stand is 20 years old and at the height of 4 m.

The PDF includes a summary in English.

• Heikurainen, E-mail: lh@mm.unknown

The effects of variations in the intensity of drainage and NPK fertilization on the natural regeneration and planting results and the subsequent development of seedling stands under various climatic conditions on drained nutrient poor pine bogs was investigated in a 16-year-old study.

Comparison of height development of Scots pine (Pinus sylvestris L.) stands on drained peatlands to that of pine stands growing in mineral soil sites show that in Southern Finland the most efficient forest improvement measures (10 m ditch spacing and 1,000 kg/ha NPK-fertilization) resulted in growth that corresponds a to a height index of a stand in a Vaccinium type site. Less efficient treatment (30 m ditch spacing and no fertilizer) resulted in growth corresponding the development of young stand in a Calluna type site. In Northern Finland the effect of fertilization on height growth was almost negligible. This is possibly due to a decrease in the nitrogen mobilization from south to north of Finland. Thus, it seems evident that fertilization of young Scots pine stands on nutrient poor drained peatlands can be recommended only in the southern part of the country.

The effect of ditch spacing is same in the whole country. The narrower the spacing the better the height growth. In the south planted stands thrive better than naturally regenerated stands, but the situation is reversed in the north.

The PDF includes a summary in English.

• Heikurainen, E-mail: lh@mm.unknown
• Laine, E-mail: jl@mm.unknown
• Lepola, E-mail: jl@mm.unknown

The aim of the paper was to describe the development of Scots pine (Pinus sylvestris L.) and Norway spruce (Picea abies (L.) H. Karst.) seedling stands on drained peatlands and to find out the principal factors influencing their growth. The material under survey consists of 180 sample plots distributed from southern coast of Finland to the Polar Circle.

The most important growth factors have been the accumulated temperature sum, site quality, drainage intensity and silvicultural condition, such as the density of the stand, the proportion of birch in the stand, and the amount of possible shelterwoods. The influence of these factors, and to some extent the influence of fertilizing, and the disturbing effects of some forest damages, such as frost, growth disturbances and elk damages were investigated. Comparisons of the development in the seedling stands on drained peatlands with the known development of seedling stands in mineral soils were made.

The PDF includes a summary in English.

• Heikurainen, E-mail: lh@mm.unknown

The present paper deals with the most important factors of peatland hydrology and the influence of forest drainage on the hydrology of peatland itself and its surroundings. It is compiled of six seminar papers written by students in the Department of Peatland Forestry in the University of Helsinki. Special attention is paid to the hydrological consequenses of the maintenance of drained areas. Also ways and measures to minimize the negative environmental effects of these treatments are discusses.

The PDF includes a summary in English.

• Heikurainen, E-mail: lh@mm.unknown
• Joensuu, E-mail: sj@mm.unknown

The study describes the relationships between a method developed by the author for the calculation of the profitability of forest drainage and the old biological method. The calculations were based on empirical data, and they aimed at finding out the effect of a variation in the profitability limit in the areas in hectares to be drained, and on the profitability of drainage. The study deals also with the profitability of present-day drainage activities. The results showed that the profitability coefficient (the ratio between the discounted increase in returns and the costs of drainage) averages 3.04 for the whole country. The corresponding value was 5.68 for Southern Finland, 3.19 for Central Finland and 1.67 for Northern Finland.

The PDF includes a summary in English.

• Heikurainen, E-mail: lh@mm.unknown

This paper presents the results of a contest performed on behalf of the Finnish bank Kansallis-Osake-Pankki and the Central Forestry Board Tapio on growing trees on peatlands. Over 5,000 sample plots were established on drained peatlands in various parts of Finland. The aim was to achieve a best possible growth of seedling stands on peatland. The factors influencing the growth of 85 best Scots pine (Pinus sylvestris L.) and 60 best Norway spruce (Picea abies (L.) H.Karst.) sample plots were studied.

The height growth of the seedling stands decreased towards the north. Fertilization seemed not to decrease the regional differences; rather on the contrary. On the other hand, fertilization increased height growth, but evidently so that the increase obtained was greater in the southern than in the northern parts of the country. Light fertilization (50 kg/ha of K₂O and 60 kg/ha of O₂P₅) caused a clear increase in height growth while heavy fertilization (100 g/ha of K₂O and 120 kg/ha of O₂P₅), had same effect but to much greater extent than the former. Spruce seedling stands in particular benefitted of the heavy fertilization.

Fertilization did not eliminate the original differences in the quality of the sites in question, but these could still be seen in the height growth after fertilization. The effect of drain spacing on the height growth was not very clear. In dense seedling stands (800 seedlings/ha) the height growth of the dominant seedlings was greater than that obtained in stands of lower density. Hold-overs caused a decrease in the growth of the seedling stands.

The PDF includes a summary in English.

• Heikurainen, E-mail: lh@mm.unknown
• Ouni, E-mail: jo@mm.unknown

This paper describes the preliminary results of Scots pine (Pinus sylvestris L.) seeding and planting trials on drained peat soils.

The results showed that a perpared peat surface was a better surface for seeding than the unprepared one. Planting of 2+1-year seedlings succeeded better than planting 1-year seedlings. Planting on the turf gave better survival than planting on the unprepared soil surface. The whole growing season was suitable time for planting Scots pine seedlings except May when the peat soil under the surface was still frozen.

Using fertilizers in connection with planting was surveyed in two ways. Mortality of seedlings increased when they were top-dressed with NPK fertilizer. Using a so-called spot fertilizing with several combinations of fertilizers resulted in K and N tending to increase the mortality of seedlings, but P decreasing mortality.

The PDF includes a summary in English.

• Heikurainen, E-mail: lh@mm.unknown
• Päivänen, E-mail: jp@mm.unknown
• Seppälä, E-mail: ks@mm.unknown

One forest drainage undertaking in Finland often consists of woodlots belonging to several owners, and over hundred owners may be involved. In the present paper a method for allocation the costs to different owners in a joint drainage undertaking is worked out. The problem has been emphasised by the new Waterways Law, which enables also such drainage projects to be undertaken to which some of the land owners oppose. In those cased the costs must be allocated according to the benefit driven by each owner from the project.

The method attempts to assess the benefits to be driven from the forest drainage, those costs of the drainage that are joint and thus subjected to allocation, and what is the area affected by drainage as used as a basis for cost allocation.

The joined costs are apportioned in the following manner. The area of peatland adjusted to differences in the benefit obtained by drainage is ascertained by the land holder by multiplying the index number by the corresponding areas. In the case of cultivated agricultural land, also an index showing the need for drainage is used in computing the adjusted area. Each topographic unit in the map is provided with a notation of its apportionment area. Joined costs are allocated to different land owners in relation to their adjusted land areas.

The PDF includes a summary in English.

• Heikurainen, E-mail: lh@mm.unknown
• Keltikangas, E-mail: mk@mm.unknown
• Seppälä, E-mail: ks@mm.unknown

The agricultural committee appointed by the Finnish Government in 1958 pointed out a problem that the rural population needed to be ensured employment and earnings from forestry. A forestry study group was called to investigate the effects of forest improvement on employment and income, on four fields: a) forest drainage, b) afforestation, c) thinning of young stands, and d) construction of forest roads. Items a, b and c increase output, and d creates outlets for timber and increases stumpage value.

The study outlined three alternative silvicultural programmes. The Basic Programme corresponds average forest management in Finland in 1953–1959. The Medium Programme can be seen conditional to the realization of the felling plan worked out in a study group Heikurainen-Kuusela-Linnamies-Nyysönen in 1961 in a committee report of Forestry Planning Committee. Finally, according to an Intensive Programme to which forest management, especially afforestation and forest drainage, will be raised to the highest possible level.

The costs of different silvicultural measures of the three programmes were estimated. The allowable cuts were calculated corresponding to the silvicultural programmes for the period 1961–1970 and 2001–2010. After calculating labour input and costs, could the increase in employment and income be estimated for the whole economy, and separately in forestry, communications and industry. When calculating the labour input required for the forest management work and road construction, the probable rise in productivity following mechanization and rationalization has been taken into account.

The PDF includes a summary in English.

• Heikinheimo, E-mail: lh@mm.unknown
• Heikurainen, E-mail: lh@mm.unknown
• Holopainen, E-mail: vh@mm.unknown
• Keltikangas, E-mail: mk@mm.unknown
• Kuusela, E-mail: kk@mm.unknown
• Möttölä, E-mail: tm@mm.unknown

About one third of the land area of Finland is covered by peatlands, furthermore, some mineral soils are troubled by excess water. Due to the prevalence of peatlands, forest drainage has been the most important form of forest improvement work. Consequently, peatlands have been an extensively studied topic within forest sciences in Finland. This paper gives a review on the central research subjects in science of peatlands, introducing little less than a hundred of the hundreds of publications published in the field. The author describes in more detail research on the formation and area of peatlands, peatland types and their suitability for forest draining, site factors on peatlands, techniques of forest ditching and the management of peatland forests.

The PDF includes a summary in Finnish.

• Heikurainen, E-mail: lh@mm.unknown

There are about 155,000 ha of fen-like pine swamps (eutrophic pine bogs) in Finland, major part of which are situated in Northern Finland. In the classification system for drainability of peatlands, this type of peatlands had been placed in the first class. The study presents a new evaluation for the peatland type, based on vegetation and tree growth.

According to a previous study, the vegetation of fen-like pine swamps can be characterised by distinctive plant communities that seem to reflect the fertility and high pH of the underlying soil. In this study, the fen-like pine swamps were divided in two subtypes based on the vegetation: proper fen-like pine swamps and fen-like pine swamps with ericaceous shrubs. Both have distinctive vegetation, which is described in the article. The distribution of the subtypes seems to be different: fen-like pine swamps with ericaceous shrubs are more common in eastern parts of Northern Finland. The two subtypes could be divided in different drainability classes according to tree growth, proper fen-like pine swamps belonging to class 1 and fen-like pine swamps with ericaceous shrubs to class 4.

The article includes a summary in English.

• Heikurainen, E-mail: lh@mm.unknown

The aim of the study was to develop an determination method to define vegetation type of fen-like pine swamps, which are combinations of two peatland types, quagmire and pine swamp. Typical for this peatland type is that the vegetation is very heterogenous. Patches of different types of plant communities are found within a small area, but in a large scale, there are only few main types of plant communities. The commonly used way to use sample plots to study tree stands suit poorly to determine the type of this kind of heterogenous ground vegetation. The article compares strip survey and circular plot survey, of which circular plot survey is determined to be less time consuming. The article describes a way to choose the locations of sample points to achieve most correct areas for different plant communities.

The article includes an abstract in German.

• Heikurainen, E-mail: lh@mm.unknown

The present investigation revealed that the influence of a forest cover on the water economy of the soil is very great in Finland. Cutting of the forest gave cause to a rise of the ground water table, which, when clear-cutting is in question, reached a magnitude of 20–40 cm. The water supplies of the soil increased 40–60 mm. In the winter, too, the ground water remaind at a lower level in the forest than in opening, however, the difference is rather small. Thinnings had same kind of effect as clear-cuttings, but the influence of even heavy thinnings was still relatively small.

The water supplies of the soil after felling decreased mainly due to the decrease in the interception in the canopy. When the water table is at the same level in the forest and in opening, evapotranspiration might be greater in the forest than in openings. However, when the water level is during the growing season considerably lower in the forest than in an opening, the evapotranspiration is strongly decreased in the forest, which means that more water is evaporated and transpirated from the opening than from the forest. Because the water table is at a higher level in the opening than in the forest, runoff from clear-cut areas has exceeded that from the forest. This means that the influence of felling on the water economy of the soil is actually even greater than indicated in this work.

The results mean that the influence of the forest cover makes up that of drainage. This affects the need for maintenance of ditches. On the other hand, the final cutting will rise the ground water strongly.

The PDF includes a summary in English.

• Heikurainen, E-mail: lh@mm.unknown

The aim of this work was to study, on the basis of material published earlier (Heikurainen 1959), the effect of temperature on stand increment, to find out if there is any differences between Norway spruce (Picea abies (L.) H. Karst.) and Scots pine (Pinus sylvestris L.), and to study the effect of site quality on the relationship between stand increment and temperature. The calculations were based on data collected from 396 sample plots on drained peatlands in different parts of Finland.

There seemed to be no differences due to tree species or site quality in the relative amounts of growth under different climatic conditions. Thus, differences in the absolute growth between poor and fertile sites are noticeably smaller in Northern Finland than in Southern Finland. The author suggests that this implies that the lasting maximal increase of growth which can be produced, for instance, by using soil-improving agents must be less in unfavourable conditions than in favourable.

• Heikurainen, E-mail: lh@mm.unknown
• Seppälä, E-mail: ks@mm.unknown

The present study deals with correlation between level of ground water table and water content of peat in peatlands drained for forestry. The results have been obtained partly from field studies and partly from experiments in the laboratory.

Both the field and laboratory experiments proved that a close rectilinear correlation exists between the level of the ground water table and the water content of surface peat. A given change in the level of the ground water table corresponds to a smaller change in the water content the deeper the peat layer examined is situated. The change in the water content in the surface layer (0–20 cm) in the cases studied was of such a magnitude that a change of 10 cm in the level of the ground water table corresponded to a change of about 5 volume per cent. In deeper layers the change was smaller. The state of equilibrium regulating the water content of the peat is relatively stable. It is possible that the so-called optimum drainage of a peatland for each tree species can be theoretically determined on the basis of the correlation between the water content of peat and the level of ground water table.

The method used in the study, the repeated weighing of peat samples in their original place, has proved to be very useful and decisively better than the method based on one-time samples. The experiment also indicate that the correlation can be determined with laboratory experiments.

• Heikurainen, E-mail: lh@mm.unknown
• Päivänen, E-mail: jp@mm.unknown
• Sarasto, E-mail: js@mm.unknown

Lowering of the ground water table is caused by decrease in the amount of water because of evapotranspiration. Evapotranspiration of a forest is determined by converting a lowering of the ground water table into a decrease in the amount of water. This paper describes a method to determine the transpiration of tree stands and ground vegetation as well as total evaporation on a Finnish drained peatland, which ground water table was relatively high, by measuring the level of the ground water table.

It was shown that in drained peatlands with relatively high ground water level, the ground water table fell during the day between about 9 a.m. and 6 p.m., and remain at approximately same level during rest of the day. The fall of ground water table was caused by transpiration of the trees and ground vegetation, and could be over 20 mm. Thus, measuring the daily lowering of ground water table can be used to estimate transpiration of the trees. When the method is applied to measuring the total evaporation of longer periods of time, also rainfall, interception, stand rainfall and stemflow have to be measured. The method is applicable only on sites with relatively high ground water level.

The PDF includes a summary in Finnish.

• Heikurainen, E-mail: lh@mm.unknown

The determination of biologically most favourable strip width in peatlands to be drained has been hindered by lack of information of the temperature conditions in the surface peat and in the air close to the ground after drainage of different intensities. Temperature measurements were carried out on peatlands drained to different degrees in Central Finland in the summers of 1960 and 1961. The ground water level in the measuring points, and the strip width served as the criterion for differences in water condition.

When the drainage became more intensive, the temperature of the surface peat decreased. However, temperature differences were small, and discernible only when the differences of water conditions were considerable. The effect of strip condition to temperature seems to be of similar nature than the ground water level. Even in extreme cases temperature differences due to different drainage intensity were relatively small, and seldom exceeded 2°C.

Differences in temperature dependent on the growing stock may be as high as 10°C. Thus, the temperature of the surface peat may be dependent on factors more important than temperature differences caused by aspects of drainage. A well-drained peatland is coldest at the beginning of a growing season compared with poorly drained peatland. The temperature differences increase deeper in the peat. This is caused by the better heat conductivity of the moist peat. Also, daily variations in temperature in the surface peat are large in moist peat.

The PDF includes a summary in English.

• Heikurainen, E-mail: lh@mm.unknown
• Seppälä, E-mail: ks@mm.unknown

The Finnish forest industry is undergoing a vast expansion, which has raised questions of forest balance. This paper studies the possibilities to increase the amount available timber by means of forest drainage. About third of the Finnish land area is peatlands. The calculations of the investigation are based on Forestry Board districts. Based on earlier studies, there is estimated to be 3,042,000 ha of true drainable swamps, 973,000 ha of poor swamps, 1,381,000 ha of uplands in need of drainage, and 1,205,000 ha of drained peatlands. Therefore, the area of drainable and drained lands totals 6,6 million ha, and requirement of forest drainage 5,4 million ha. The drainage hardly reaches this extent, however. It can be assumed that part of the poor swamps is uneconomical to drain. In addition, a half of the paludified forest land will probably not be drained. Thus, it can be estimated that the area to be drained in the future is about 5 million ha. It seems possible that this area could be drained within about 50 years with the present draining capacity.

Draining of all objects of forests would increase the annual increment of our forests, in time, by about 10.5 million m³. This would signify an increase of 23% compared to the present growth of the forests. The increase in the growth consists mainly of softwood: 16% is birch, and the remaining 84% almost equally of Scots pine and Norway spruce. The increase of growth is relatively slow. Depending on the rate of the drainage program, the mean increase of growth will be reached in about 25–35 years. The increase in removal indicated by the increase in the mean increment will be reached in only 50–60 years.

The PDF includes a summary in English.

• Heikurainen, E-mail: lh@mm.unknown

This paper is a review on the silvicultural research in Finland, researchers and the main subject of the research within the previous 50 years. The task of silvicultural research is to serve forest management work and create a foundation for the practical operations, on one hand, and to answer to the constantly arising questions in the practice of forest management, on the other.

It can be said that the forestry as an independent branch of science began in 1909. At first the research was primarily biological, dealing with both the foundations and practices of silviculture. The main subjects are divided to forest sites and vegetation, biology of trees and stand, and methods of forest management.

The article is published in Finnish in separate PDF Acta Forestalia Fennica vol 70 no 3.

• Mikola, E-mail: pm@mm.unknown
• Kangas, E-mail: ek@mm.unknown
• Heikurainen, E-mail: lh@mm.unknown

This paper is a review on the silvicultural research in Finland, researchers and the main subject of the research within the previous 50 years. The task of silvicultural research is to serve forest management work and create a foundation for the practical operations, on one hand, and to answer to the constantly arising questions in the practice of forest management, on the other.  

Forestry as an independent branch of science began in 1909. At first the research was primarily biological, dealing with both the foundations and practices of silviculture. The main subjects are divided to forest sites and vegetation, biology of trees and stand, and methods of forest management. 

The article is published in English in separate PDF Acta Forestalia Fennica vol 70 no 4. 

• Mikola, E-mail: pm@mm.unknown
• Kangas, E-mail: ek@mm.unknown
• Heikurainen, E-mail: lh@mm.unknown

This investigation is part of series of studies aiming at defining the present condition and growing stock of drained peatlands. The studies were conducted in 1955–1957. The first part concentrates on the state of the areas, and second part the growth and volume of the stands.

Condition of the drained peatlands, a total of 45,224 ha, in Southern and Northern Finland, was studied occularly as surveys by stands. The stands to be studied were chosen randomly. Drainage effect of the areas proved to be relatively good especially in Southern Finland in private lands. In Northern Finland in the State forests, however, were many drained areas with poor drainage effect. Many of these were preliminary drainages that had not been continued. Others had too sparse drainage system, the planning was insufficient or the ditches had deteriorated. The need for supplementary draining should be considered. The condition of the ditches in old draining areas was relatively weak. This can be problematic especially in private lands. Therefore, the ditches should be planned in a way that minimizes the need for repair. The silvicultural state of the forests was poor, mostly because forest management, and sometimes regeneration had been neglected.

A total of 1,368 sample plots were measured to determine the growing stock of the studied stands. The country was divided in five climatic zones to determine local variations in the growth. The material covered large variation of peatland types. The growth of different spruce swamp types had increased close to the mineral soil sites, but especially in originally treeless or sparcely wooded stands the growth was still poor. In addition to fertility of the peatland type, the climate zone had strong effect on the volume of the stands when similar peatland types were compared. Tree species composition seemed to be strongly determined by the peatland type. Against previous understanding thickness of the peat layer had little effect on the growth of the trees, and shallow peat layer proved not to improve the drainability of a peatland.

The PDF includes a summary in German.

• Heikurainen, E-mail: lh@mm.unknown

Draining transforms root systems of trees growing in peatlands towards the ones growing on mineral soil. However, even after efficient draining the root systems differ from the root systems of trees growing on mineral soil. This investigation concentrates on root systems of forests of similar mire types growing in similar draining conditions but having different tree species compositions. The peatland, situated in Pieksämäki in Southern Finland, was drained in 1937. Sample plots, measured in 1956, consisted of mixed forest of Scots pine (Pinus sylvestris L.), Norway spruce (Picea abies L. Karst.) and birch (Betula sp.) in different compositions, and were in natural condition.

The sedge pine bog studied in this investigation was shown to have larger total amount of roots and mycorrhiza than in previously studied dwarf shrub pine bogs. This reflects better growth conditions of the better site. The depth of root system was, however, similar. Root systems of birch were deeper than those of the coniferous tree species. Differences between Scots pine and Norway spruce were small. Corresponding differences between the species were found in the density and total number of mycorrhizas. The abundance of mycorrhizas in the roots of birch increased in deeper layers of peat, but decreased especially in spruce roots. In earlier studies the abundance of mycorrhizas decreased in the roots growing in deeper layers in pure Scots pine stands, but no such variation was seen in this study. The result suggest that the deep root system of birch may affect also the root systems of the coniferous trees. On the other hand, birch roots can have advantage over the coniferous trees.

The PDF includes a summary in German.

• Heikurainen, E-mail: lh@mm.unknown

The article deals with forest ditches dug by manual labour in drained peatlands in Central and Southern Finland, ranging in age from 16 to 25 years. The ditches have been allowed to develop in a natural state. A total 1,160 of randomly selected sample plots were studied.

The results show that the originally dug ditch depth has not been the decisive factor from the viewpoint of maintaining the ditch repair. Ditches dug in thick peat layer have maintained their repair better than those dug in thin peat layer. Apparently, the influencing factor is the type of soil, to a certain extent parallel to the thickness of peat layer. In ditches dug mainly in mineral soil, the type of soil has essentially contributed to maintaining the ditch repair. Ditches in coarse-grained soils maintained a better repair than those in fine-grained soils. Also, the steeper the gradient of the ditch the better the ditch repair has been maintained. There was no relationship between the thickness of peat and the filling up of ditch bottom, because of the influence of mineral soil. Filling up of a ditch seems to be mainly due to the sinking of peat. The filling up of ditch bottom was more pronounced in clay-silt soil than in other soil types. The filling up of ditch bottom by varying gradient is due to the fact that with a small gradient the speed of water is so slow as to permit the soil particles to sink to the bottom. Another factor affecting filling up of the ditches is wetness of the peatland. Deepening of ditches happens mainly through erosion, if the gradient is large enough. The study suggests that a 50-m spacing with about 60-cm ditchc depth would be most profitable.

The PDF includes a summary in English.

• Heikurainen, E-mail: lh@mm.unknown

The root system of a Scots pine (Pinus sylvestris L.) growing on a peatland is restricted, according to earlier studies, on the top layers of the peat above the groundwater level. Drainage of the peatland affects growth of the root system. This investigation aims at studying the root systems on the point of view of draining of peatlands. The structure and distribution, and the growth of mycorrhiza in Scots pine roots in pine swamps varying from natural state to well drained state is studied.

The study shows that Scots pine on pine swamps has more extensive root system than has earlier assumed, it is common to find 1,000 m of roots in one cubic meter in a healthy stand. The trees reach this density of roots early on. In a drained peatland, the total root length is markedly higher than in a similar stand in natural state. The root systems proved to be very shallow. Even in a well-drained site the roots did not grow deeper than 20 cm. 70% of all roots were found in the upper 5 cm layer of peat, and 90% in the upper 10 cm layer. Root systems were deeper in drained peatlands, but the difference was small. In a site in natural state the average depth of the roots was 4 cm, and in a drained site 5 cm. About 85% of the roots were under 1 mm of diameter. Short roots were found only in the fine roots. Draining increases strongly the number of short roots. Mycorrhizas of the types A, B, C and D as well as pseudomychorrizas were found in the pine roots.

The PDF includes a summary in German.

• Heikurainen, E-mail: lh@mm.unknown

The seasonal changes of the roots systems of a pine stand on the peatlands have been studied with samples collected during summers 1952-1954 and winter 1955. There are altogether seven sample areas that are located in the district of Korkeakoski.  

The amount of roots is at the smallest in the spring, increasing then rapidly and peaking at the end of July. After that the amount of roots decreases again against the winter to the same size than in the spring. Variations seem to be similar in every year and also similar to other studies on mineral soils.

The PDF contains a summary in Finnish. 

• Heikurainen, E-mail: lh@mm.unknown

Pine swamps are easily regenerated by natural regeneration of Scots pine (Pinus sylvestris L.). Usually seeding felling is used, but also strip system or clear cutting and regeneration along stand edge has been suggested. This article discusses the regeneration by clear cutting and sparing the existing undergrowth. The article focuses on pine swamps to be drained and the ones in natural state.

Pine swamps in natural state usually have plenty of trees of smaller diameter classes, that can be trusted to form the future tree generation after the felling. This shortens the rotation by 20-30 years. The undergrowth has been shown to recover quickly. The method suits for regeneration of drained peatlands but could fit also for regeneration of pine swamps in natural state.

The seedlings in the pine swamps are mainly 1-5 years old, and the stock is changing. It seems that larger trees produce a wider selection of age groups, but the seedlings survive longer under smaller mother trees. Part of the younger generations of seedlings seem to be destroyed when the peatland is drained. Further studies are needed to investigate how the draining and felling are to be performed to spare the young seedlings.

The Acta Forestalia Fennica issue 61 was published in honour of professor Eino Saari’s 60th birthday.

The PDF includes a summary in German.

• Heikurainen, E-mail: lh@mm.unknown

The paper presents some preliminary results of a 10-year-old study the purpose of which is to determine the effect of simultaneous variations in the intensity of drainage and fertilization on the development of planted and natural seedlings on peatlands under various climatic conditions. The development of the Scots pine (Pinus sylvestris L.) seedlings appeared to be better the more intensive the degree of drainage and fertilization used. The increase in the temperature sum had a positive effect on the development of pine seedlings and decreased the mortality rate.

The best growth result was obtained with a 10 m ditch spacing and strong fertilization. As it is difficult to decrease the 10 m ditch spacing for cost reasons, it can be concluded that on such oligotrophic peatlands as were used in this experiment, only an average growth level in the seedling stands can be reached even with the most efficient forest improvement measures. Broadcast fertilization used in the experiment, at least in large doses, increases seedling mortality, as well as the coverage of the ground vegetation, particularly that of cottongrass and fireweed, and also the shrub height, thus increasing competition. It cannot be recommended for afforestation, and today spot fertilization is used. According to this experiment natural seedlings seem once they have recovered after the first years, to grow better than the planted seedlings. This was true especially in the north and in areas, where drainage was not efficient. The height and height growth of the seedlings were to a large extent dependent on the temperature sum.

The PDF includes a summary in English.

• Heikurainen, E-mail: lh@mm.unknown
• Laine, E-mail: jl@mm.unknown

The study deals with the development during the 1950s and 1960s of a stand growing on peatlands which had been drained in the 1930s. The following characters were determined by measurements: the volume of the growing stock, the volume increment, the relative increment, the increment percent and the increment curves. Moreover, the possible changes taking place in the difference between tree growth along the ditches and in the middle of the strip between ditches were studied. In addition, the regional variation in increment was studied; this question was studied as the regression between the relative growth and the temperature sum. The results were compared with other Finnish investigations into the regional variation of increment.

The volumes of the growing stock had increased during the course of twelve years by 70–10 m³ /ha depending on the site type and climatic zone concerned. The relative increment had dropped in each case studied. As a matter of fact, this is only to be expected because the volumes had increased and the absolute growth had remained more or less unchanged. The development of the increment percent was compared with mineral soil stands in the case of Southern Finland, both uncut stands and stands treated with cuttings. According to the results obtained, the development of the increment percent was better in the present material than in uncut forests, but in some cases it did not reach the level of tended stands. The revival of the tree crop after draining takes place at different rates in the vicinity of and, on the other hand, at greater distances from the ditches and that this relationship is dependent on the fertility of the site.

The PDF includes a summary in English.

• Heikurainen, E-mail: lh@mm.unknown
• Seppälä, E-mail: ks@mm.unknown

The study is a part in a more comprehensive series of investigations into the profitability of forest improvement measures. The present paper describes a new method for calculation of the suitability of various peatlands for forest drainage. According to this method, the net profit is calculated as the difference between the gross profit and the costs, and the profitability coefficient, as the ratio between the gross profit and the costs. The most important factors used for calculation of the gross profit and the costs are as follows: the site quality index, the volume of the tree stand capable of development at the time of draining, the temperature sum and the stumpage development at the time of draining, the temperature sum and the stumpage price. For use in the field, simplified auxliary tables have been worked out.

The PDF includes a summary in English.

• Heikurainen, E-mail: lh@mm.unknown

In 1965 and 1966 a total of 25 experiments were laid out in various parts of Finland in order to find out the effect of simultaneous variation in the intensity of drainage and fertilization on the development of plantations and natural seedling stands of Scots pine (Pinus sylvestris L.) growing on pine swamps. The fertilizer used was Y fertilizer for peat soils, a fertilizer mixture containing 14 % N, 18 % P₂O₅ and 10 % K₂O. It was applied in rates of 500, 1,000 and 1,500 kg/ha. The ditch spacings studied were 10, 20 and 30 m. The present paper is a preliminary report on a series of studies, the experiments will be observation for a total of 15–20 years.

Mortality of the planted seedlings was found to be the higher after the first growing season, the larger the quantity of fertilizer that had been applied. Fertilizing caused an increase in seedling mortality even after the first growing season following application. At the end of the fifth growing season the height of both natural and planted seedlings is the greater, the larger the quantity of fertilizer that has been applied. Analysis of the height growth of the seedlings showed that larger quantities of fertilizer did not increase growth in the same proportion. The occurrence of growth disturbances is the greater, the more fertilizer has been applied.

Fertilization also changed the composition of ground vegetation. The in the beginning of the experiment  birch (Betula sp.) was absent in the area, but was found in the stands the greater abundance the higher application of the fertilizer.

From the viewpoint of growth of the seedlings the best results were obtained with the greatest intensity of fertilization and the narrowest ditch spacing used in the study. The results also show that strong fertilization and a high degree of drainage intensity are not capable of bringing about any particularly good growth on peatlands which originally are relatively poor in nutrients. The growth values now obtained equal only one third of those obtained on peat soils of greater fertility.

The PDF includes a summary in English.

• Heikurainen, E-mail: lh@mm.unknown
• Veijola, E-mail: pv@mm.unknown

The present study deals with the ground water table in the soil of drained peatlands and with the technique used for its determination. The terms depth and height of the ground water table are defined in the paper. Because of the fact that the surface of peatlands moves under the influence of a great number of different factors, the depth of the ground water table and the height of the ground water table are not parallel concepts. The present paper concentrates on the depth of the ground water table.

Observations on the depth of the ground water table in the sample plots in 1966-67 and 1968-69 show that the maximum of the late summer usually exceeds that of the early spring, and that the minimum occurring in the period of snow melting is more clearly discernible than that of the fall. Great differences occur in the depths of the ground water table in different sample plots. These differences are due to the specific properties of the peat of different peat layers, which are expressed in terms of the ground water coefficient. The duration of the depth of the ground water table proved to be a useful way to express the long-term changes.

Four kinds of short-term fluctuations in the ground water table were observed: a) the ground water table falls during the night hours, although the rate of falling is slower than in daytime, b) the ground water table rests at the same depth during the night, whereas during the day it clearly falls, c) the descent of the ground water table is similar throughout the whole 24-hour period, d) the ground water table rises during the night hours and falls in daytime. Occurrence of these types are discussed. Typical short-term fluctuation is the fall due to evaporation in the daytime.

The third part of the paper discusses the techniques used to measure the changes in ground water table.

The PDF includes a summary in English.

• Heikurainen, E-mail: lh@mm.unknown

The aim of this study was to assess the effect of cutting of different intensities on the hydrology of drained peatland. The study concerned with measuring changes in the ground water level, throughfall, and snow cover, and specially runoff. This study focused on the phenomena that occur during the growing season. Seven sample plots were measured in an area in Central Finland which had been drained about 50 years earlier and had Scots pine (Pinus sylvestris L.) stand of uniform age.

To survey the hydrological effects of cuttings, 20%, 40% and 60% of the stand volume was removed in thinnings. In addition, one sample plot was clear-cut. During the first two years after cutting the interception diminished, and throughfall increased by 7% for the 20% thinning, by 8% for the 40% thinning and by 12% for the 60% thinning. Clear cutting increased the throughfall by 29%. The thinnings increased the depth of the snow cover the more the heavier the thinning.

Even the lightest thinning raised the ground water table, but the difference between 20% and 40% thinning was not marked. Cuttings increased runoff the greater the heavier the cutting. The hydrological changes of fellings were detrimental for the site. However, there was a marked change only between the 40% and 60% thinnings. Fertilization had a favourable effect on the hydrology of the peatland by increasing the depth of ground water table, and decreasing the throughfall.

The PDF includes a summary in Finnish.

• Heikurainen, E-mail: lh@mm.unknown