Silva Fennica vol. 27 | 1993

Abundant snowfalls and thick snow cover influence forest ecology mainly in two ways. Snow loading increases the number of damaged stems, which increases the amount of decay in stems, in its turn important for many animals. Second, the ground remains unfrozen under the snow cover, which is of crucial importance for many perennial species of ground vegetation. These winter phenomena also have influenced the early Finnish culture as man in his everyday life in the wilderness was in close contact with nature. In this paper, ecological interactions between snow conditions, forest flora, fauna and early culture are discussed mainly with reference to the province of Uusimaa in Southern Finland.

• Solantie, E-mail: rs@mm.unknown

Drying of pulpwood bolts of Scots pine (Pinus sylvestris L.), birch (Betula spp.) and Norway spruce (Picea abies (L.) H. Karst.) was studied by measuring the drying of sample bolts placed in experimental piles. The results revealed that the main factors affecting timber drying are debarked surface area, moisture content at the time of felling and the size of the bolt. Furthermore, pine and spruce bolts located in the upper part of the pile dry better than bolts near the ground.

The investigation of green weight changes of whole piles of pine and birch was based on data collected in 1987–91. The green weight of piles was dependent mainly on storage time and on region; effect of weather variables could not be distinguished. Specific calibrating coefficients for motor-manual and mechanical cutting were included in the green weight equations.

Comparison between green weight equations and detected weight losses of sample piles indicates that fitted models seem to produce at least approximate results for the green weights, the said results thus lending themselves to be utilized as part of a transportation cost model.

The PDF includes an abstract in Finnish.

• Kokkola, E-mail: jk@mm.unknown

The survival of forest tree species in wildfires was examined on two burned stands. Norway spruce (Picea abies (L.) H. Karst.) and birches (Betula spp.) proved to be sensitive to the effects of wildfire; almost all individuals of these tree species were killed by the fires. Scots pine (Pinus sylvestris L.) was more tolerable to the effects of wildfire; i.e. one out of five Scots pines survived. Fire tolerance increased as tree size increased.

The PDF includes an abstract in Finnish.

• Kolström, E-mail: tk@mm.unknown
• Kellomäki, E-mail: sk@mm.unknown

Regression models for estimating stem volume of Scots pine (Pinus sylvestris L.) were constructed using sample tree data measured in the 7th and 8th National Forest Inventory of Finland. Stem volume were regressed on diameter, basal area of growing stock, and geographic location. The results of the study show that using second order trend surface to describe the geographic variation of the residuals gives satisfactory results. Using mixed estimation for combining old and new sample tree data improves the efficiency of an inventory. The weight of the prior information must be low, because remarkable differences in stem form was found in the two inventories.

The PDF includes an abstract in Finnish.

• Korhonen, E-mail: kk@mm.unknown

In the method presented in this study, a group of experts evaluate, in a pairwise manner, a set of forest areas with respect to the game species considered. On the basis of these comparisons, relative priorities of forest areas are estimated using the eigenvalue technique. Using regression analysis, a habitat suitability function is estimated in which the priority is predicted by measures already familiar in forest planning. As a case study, a habitat suitability function was estimated for black grouse (Tetrao tetrix, Lururus tetrix L.). The function is applicable in forestry planning carried out using modern planning techniques.

The PDF includes an abstract in Finnish.

• Kangas, E-mail: jk@mm.unknown
• Karsikko, E-mail: jk@mm.unknown
• Laasonen, E-mail: ll@mm.unknown
• Pukkala, E-mail: tp@mm.unknown

According to a recently presented hypothesis, the predicted climatic warming will cause height growth onset of trees during mild spells in winter and heavy frost damage during subsequent periods of frost in northern conditions. The hypothesis was based on computer simulations involving a model employing air temperature as the only environmental factor influencing height growth onset. In the present study, the model was tested in the case of eastern Finnish Scots pine (Pinus sylvestris L.) saplings. Four experimental saplings growing on their natural site were surrounded by transparent chambers in autumn 1990. The air temperature in the chambers was raised during the winter to present an extremely warm winter under the predicted conditions of a double level of atmospheric carbon dioxide. The temperature treatment hastened height growth onset by two months as compared to the control saplings, but not as much as expected on the basis of the previous simulation study. This finding suggests that 1) the model used in the simulation study needs to be developed further, either by modifying the modelled effect of air temperature or by introducing other environmental factors, and 2) the predicted climatic warming will not increase the risk of frost damage in trees as much as suggested by the previous simulation study.

The PDF includes an abstract in Finnish.

• Hänninen, E-mail: hh@mm.unknown
• Kellomäki, E-mail: sk@mm.unknown
• Laitinen, E-mail: kl@mm.unknown
• Pajari, E-mail: bp@mm.unknown
• Repo, E-mail: tr@mm.unknown

The paper discusses the principles of forest management in the state forests of Finland, and the contradictions in choosing between the different land uses. These principles of the forest management are sustainable use of natural resources, economic and effective management, and taking in account nature conservation, protection of environment, recreation services and employment issues in all activities of the Forest Service. Even regional policy affects the management planning in the state forests.

• Kotimäki, E-mail: tk@mm.unknown

Forests have been economically important for Finnish private forest owners at all times, but the use of forests has changed markedly since 1920s, when forests were mainly used for collecting household timber, and the cuttings were often exploitative because of the farmer’s need for money. The present situation is totally different. Need for household timber is marginally small, and private forestry produces mainly timber for sale. The sales of timber have increased, but due to better forest management the growing stock in the private forests has increased. The article discusses how the changes in values of forest owners has and will affect the stage of private forestry.

• Järveläinen, E-mail: vj@mm.unknown

The paper discusses how the general trend towards increasing growth and productivity in the European societies is expressed also in forestry. It is reflected, for instance, in the increasing production and productivity of forest industries. Technological progress and call for economic growth require great flexibility from all resources. These pressures for effectiveness and production also concern Finnish forestry and forest management. Industrialization, urbanization and development of forestry have increased the pressure to use forests in recreation, preserving human environment and nature conservation in addition to production of timber. Through the development the definition of sustainability has become wider.

• Vehkamäki, E-mail: sv@mm.unknown

The paper deals with the application of forest dynamics. Reference is made to two studies, which have been carried out at a national level. The simulations of forest decline as well as the production of exceedingly thick timber of spruce and fir provide various examples of the major problems of forest simulation and of some possible solutions. It is pointed out that the statistical analysis of empirical data is most important for modelling and it might bring about even more valuable results than the ultimate simulation itself.

• Sekot, E-mail: ws@mm.unknown

There is some evidence to support the hypothesis that crown form of Scots pine (Pinus sylvestris L.) can be inherited either mono- or polygenically. In Finland, a narrow, horizontal whorl-layer structure is striking in about one half of the offspring of a genotype E 1101, ”Kanerva pine”. The offspring are characterized by a narrow crown, short and thin branches at an angle of 90° to the stem, minimal tapering and by numerous long, lateral shoots, long needles and the common occurrence of three-needled fascicles among the dwarf shoots. These features are connected to a high growth rate, a high harvest index and to tortuosity of the stem. It is suggested that this complex of characters is determined by a single dominant gene.

In this study, several offspring of the E 1101 were classified into three form types in seven sets of progeny test data, including progenies of various ages having E 1101 as either maternal or paternal parent as well as open pollinated progenies of second-generation offspring. A segregation close to 1:1 was found both in the first and in the second-generation progenies when wilds and intermediates were combined and compared with Kanervas. The result indicates that the three types of Kanerva form can be due to a single dominant allele (K). Kanervas are heterozygous (Kk) for the allele and wilds are recessive homozygotes (kk) resulting 1:1 segregation in their progenies. However, there were also remarkable deviations from the expected distribution. The differences as well as the inheritance pattern are discussed.

The PDF includes an abstract in Finnish.

• Pöykkö, E-mail: tp@mm.unknown
• Velling, E-mail: pv@mm.unknown

Coniferous and non-coniferous fine root and rhizome production was measured after one growing season using the ingrowth bag method in Scots pine (Pinus sylvestris L.) stands differing in ages from 7 to 105 years in Southern Finland. Total fine-root production decreased from the 7-year to 20-year-old stands, and then increased slightly in the 85- to 105-year-old stands. Most of the total fine-root biomass in the youngest age groups came from non-conifer species, whereas most of the total fine-root biomass in the three older age groups came from conifer species. The maximum coniferous fine-root production was found to occur at crown closure in the 11- to 13-year-old stands. Rhizome production was the lowest and highest in the 20- and 85- to 105-year-old stands, respectively. The increase in rhizome production in the 85- to 105-year-old stands was associated with an abundant understory cover of Vaccinium myrtillus and V. vitis-idaea and an increase in light penetration. The ingrowth bag method was found to be useful in assessing the relative fine-root production among species-group and successional stages of Scots pine stands.

The PDF includes an abstract in Finnish.

• Messier, E-mail: cm@mm.unknown
• Puttonen, E-mail: pp@mm.unknown

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

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

Mixed linear models were constructed to describe the height development of Norway spruce (Picea abies (L.) H. Karst.) and Scots pine (Pinus sylvestris L.) advance growth after release cutting. The models related density of the overstory, time elapsed since release cutting and tree size with annual height increment. Parameters of preliminary models were estimated from a limited data set to judge the feasibility of the approach for further studies.

The PDF includes an abstract in Finnish.

• Koistinen, E-mail: ek@mm.unknown
• Valkonen, E-mail: sv@mm.unknown

Model-based information systems have proved valuable planning tools for analysing the production possibilities of forests as well as for understanding forest resources dynamics, stand management practices and forest economics. Computerized forest models implemented in the users’ information systems facilitate the transfer and application of research results in practical forestry.

Conclusions and visions concerning modelling are drawn from experiences in developing the MELA system and its application in solving timber production problems on both the national and forest holding level in Finland. The precondition for predicting forest resource dynamics and for planning the utilization of forests is to accept conditions, uncertainties and a restricted period of time.

The interactive process of forest resource, growth and drain monitoring, and forest management planning supported by forest research and modelling, are the means to enable an operational information base for a dynamic regulation and adaptation strategy for forest resource management under changing conditions and uncertainty.

The PDF includes an abstract in Finnish.

• Siitonen, E-mail: ms@mm.unknown

Europe’s forest area has increased 5 million ha since the late 1960s. The growing stock has increased 43% and the net annual increment 55% in exploitable forests since 1950. A part of the reported increase is caused by sampling inventories, which have been made in greater part of the countries. Sampling inventories have corrected earlier underestimates of the growing stock and the increment.

The difference between the annual net increment and fellings has increased since 1950. The net increment, 584 million m³, exceeded fellings, 408 million m³, by 176 million m³, in exploitable forests in 1990. If fellings could be increased to equal the increment, Europe would be an exporter of forest products.

A greater increase in the density, in the age and in the mean volume of forests per hectare threaten the biological stability of the growing stock. Degrading of the stock, increasing natural losses and deteriorating environmental qualities of forests can only be prevented by increased fellings and by forest regeneration.

The PDF includes an abstract in Finnish.

• Kuusela, E-mail: kk@mm.unknown

A range of different indices are available for assessing the health of trees in forests. An even larger range can be used for the assessment of the health of forest ecosystems. Most studies made in connection with ”forest decline” and the impact of air pollution and other environmental stresses on forests have concentrated on the assessment of crown transparency and crown discoloration in individual trees. These are non-specific indicators which are now known to be sometimes of relatively little value when determining the health of a forest ecosystem. Numerous problems exist with both, and the standardisation of assessments between and even within countries has not been achieved. Consequently, studies claiming to compare ”defoliation” between different countries cannot be substantiated. The emphasis on crown transparency and crown discoloration has resulted in the neglect of a number of other indices that could be of considerable value. These include a variety of visual measures of crown condition and also several non-visual bioindicators. Some of these techniques are objective, reducing the present reliance on observed standardization. A large number of potential techniques are currently at the research stage and have yet to be adequately tested in field trials. This represent an area where a substantial amount of further research is required.

• Innes, E-mail: ji@mm.unknown

Moose (Alces alces L.) browsing was studied in young Scots pine (Pinus sylvestris L.) stands mixed with deciduous trees in high-density winter ranges. The proportional use of twig biomass decreased as the availability increased. The total as well as proportional biomass consumption were higher on the moist than on the dry type of forest. The per tree consumption of pine was higher on the moist type, where the availability of pine was lower. Deciduous trees were more consumed on the moist type, where their availability was relatively high. The consumption of pine saplings increased as the availability of birch increased. Pine stem breakages were most numerous when birch occurred as overgrowth above pine and at high birch densities. The availability of other deciduous tree species did not correlate with browsing intensity of Scots pine. Moose browsing had seriously inhibited the development of Scots pines in 6% of the stands, over 60% of available biomass having been removed. Rowan and aspen were commonly over-browsed and their height growth was inhibited, which occurred rarely by birch. There was no difference in the proportion of young stands in forest areas with high and low moose density. A high proportion of peatland forests was found to indicate relatively good feeding habitats in the high-density areas.

The PDF includes an abstract in Finnish.

• Heikkilä, E-mail: rh@mm.unknown
• Härkönen, E-mail: sh@mm.unknown

Measurements of wind and subsequent swaying of two Scots pines (Pinus sylvestris L.) were made at stand edge conditions. The horizontal windspeed was measured ten meters outside of the stand edge for four heights using cup anemometers. The compass directions were determined using a directional vane placed above the canopy. Tree swaying was measured by accelerometers at xy-coordinates. The shape of the wind profile at the stand edge varied to some degree depending on windspeed, but the form was a logarithmic one. Swaying of trees increased along with increasing windspeed. Furthermore, swaying was more or less irregular in relation to xy-coordinates, but it occurred, however, mainly perpendicularly to the direction of mean windspeed. The maximum bending of trees to the direction of mean windspeed varied also only little for various gusting windspeeds (average windspeed of 20 seconds) and dynamic wind loads. The maximum bending of trees was also in most cases less or equal to those predicted on the basis of static wind loads, when the mean windspeed for static load is taken as equal to the gusting windspeed.

The PDF includes an abstract in Finnish.

• Peltola, E-mail: hp@mm.unknown
• Aho, E-mail: ja@mm.unknown
• Hassinen, E-mail: ah@mm.unknown
• Kellomäki, E-mail: sk@mm.unknown
• Lemettinen, E-mail: ml@mm.unknown

A model for the mechanism of windfall and stem breakage was constructed for single Scots pine (Pinus sylvestris L.) at the stand edge. The total turning moment arising from the wind drag and from the bending of stem and crown was calculated along with the breaking stress of the stem. Similarly, the support given by the root -soil plate anchorage was calculated. Windspeed variation within the crown and the vertical distribution of stem and crown weight were taken into account. Model computations showed that trees having a large height to diameter ratio were subjected to greater risk of falling down or breaking than trees with a small height to diameter ratio. The windspeed required to blow down a tree or break the stem of a tree decreased if the height to diameter ratio or the crown to stem ratio of trees increased.
The PDF includes an abstract in Finnish.

• Peltola, E-mail: hp@mm.unknown
• Kellomäki, E-mail: sk@mm.unknown

The water retention characteristics and their variation in tree nurseries and related physical properties were determined for commercially produced growth media made of light slightly humified Sphagnum peat. A total of 100 samples of peat media were collected from filled seedling trays in the greenhouses of four Finnish nurseries in 1990. In addition, the physical properties were determined for two growth media made of compressed peat sheets and chips. The variation in water retention characteristics in nurseries was described using linear models with fixed and random effects. The sources of variation in the mixed linear models were producer, grade, batch (greenhouse) and sample (tray).

The water retention of the peat media at different matric potentials was comparable to that given in the literature. The media shrank an average of 0–16% during desorption. The peat grades were finer than the Nordic quality standards for peat growth media. Particles < 1 mm increased and particles 1–5 mm decreased the water retention characteristics measured. The greatest total variation in water retention was at -1 kPa. The water retention of the peat media differed least at -5 and -10 kPa. The water retention characteristics of media from different producers usually differed significantly. The grades, on the other hand, did not differ from each other in their water retention characteristics nor were there significant interactions between producer and grade. The batch effect was marked but was lower than the effect within batches, where the sample (tray) effect was greater than the effect due to random measurement error. At -10 kPa, the measurement error was, however, clearly greater than the sample effect. The random measurement error was comparable to the batch effect. Aeration of the growth media is dependent on the water content retained between saturation and -1 kPa. The water availability to seedlings at the nursery phase is affected mainly by water retention between -1 and -10 kPa.
The PDF includes an abstract in Finnish.

• Heiskanen, E-mail: jh@mm.unknown

This paper presents the publishing guidelines of the Finnish Society of Forest Science for the forest scientific series of Silva Fennica. This paper presents the instructions to authors in Finnish, the English instructions are included in a separate PDF.

• Finnish Society of Forest Science, E-mail: –

This paper presents the publishing guidelines of the Finnish Society of Forest Science for the forest scientific series of Silva Fennica. This paper includes the instructions to authors in English, the Finnish instructions are in a separate PDF. 

• Finnish Society of Forest Science, E-mail: –

The paper discussed the definitions of different Finnish and English terms concerning timber harvesting, and suggests definitions and translations of the terms.

• Kantola, E-mail: mk@mm.unknown
• Harstela, E-mail: ph@mm.unknown

The paper, presented at the seminar ”Forestry in Europe: Implications of European Integration for National Forestry”, discusses the effects of first Forestry Action Programme in the European Community, UNCED 1992, the European Community’s new Forestry Strategy and the second Forestry Action Programme directives of conservation of habitats on forestry within the EC.

• Koch, E-mail: nk@mm.unknown

The paper, presented at the seminar ”Forestry in Europe: Implications of European Integration for National Forestry”, discusses the meaning of the European Community for the forestry sector, putting a special emphasis on recycling. Subsidies and the so-called ”Forestry Action Program” are among the topics that have raised controversial discussions within the EC. In addition, wood fibre recycling and the EC draft directive on packaging waste includes ambiguous targets for recycling.

• Wermann, E-mail: ew@mm.unknown

Seedlings from four Norway spruce (Picea abies (L.) H. Karst.) stands originating from areas with effective temperature sums ranging from 710 d.d. to 1,150 d.d. were raised under artificial light and temperature treatment. After a 10-week growing period the hardening process was started by subjecting the seedlings to +8°C night temperature and +15°C day temperature, and increasing the night length by 1.5 hour/week. Hardiness was measured by means of artificial freezing treatment (-10°C or -15°C), followed by visual estimation of the degree of needle injury. The stem height, lignification and bud development were measured before the freezing treatment. The amount of injury increased the more southern the origin of the tested material was. Furthermore, the proportion of non-lignified part of the seedling stem was negatively correlated with the latitude of the provenances. The proportion of seedlings with clearly visible buds was more than 90% in the northernmost entry and less than 1% in the southernmost one. The overall correlation coefficient between the needle injuries and the proportion of non-lignified part of the stem was rather high, but varied considerably from 0.3 in the northernmost material to over 0.6 in the southern provenances. According to the results, it seems to be possible to use growth characteristics as an indicator of frost hardiness at the provenance level.
The PDF includes an abstract in Finnish.

• Pulkkinen, E-mail: pp@mm.unknown

There exists an algorithm for construction interpolating quadratic splines which preserves the monotony of the data. The taper curves formed with this algorithm, QO-splines, have many good qualities when a sufficient number of measured diameters of a tree is available. In fact, they may even be superior to certain shape preserving taper curves, MR-splines. This algorithm can be modified to preserve also the shape of the data. In the present paper, the quality of taper curves constructed by a new shape preserving from of the algorithm is examined. For this purpose, taper curves are formed for different sets of measurements and their properties are compared with the ones of QO-splines and MR-splines. The results indicate that these new shape-preserving taper curves are in general better than QO-splines and MR-splines even if the differences may be small in many cases. The superiority is the clearer the less measurements are available.

The PDF includes an abstract in Finnish.

• Lahtinen, E-mail: al@mm.unknown

Three Scots pine (Pinus sylvestris L.) plantations carrying 35 plots with initial spacings from 800 to 5,000 plants/ha were studied. Planting designs varied from a square to a rectangle with 5-metre row distance, the plant-to-plant distance being 0.8 metres. At current dominant height of 6 m, rectangularity had no effect on height, diameter, or volume growth of trees. Slight ovality of stems was observed in rectangular plots but the differences in the cross-wise mean diameters were very small, not over 1.1 mm in terms of plot-wise means. The diameter of the thickest living branch of a tree was linearly dependent of the dbh. The branches were clearly thicker between the planting rows at under 1,600 stems/ha stand density. A non-square planting pattern is a conceivable alternative when the line corridors suitable for mechanized silvicultural operations are preferred.
The PDF includes an abstract in Finnish.

• Salminen, E-mail: hs@mm.unknown
• Varmola, E-mail: mv@mm.unknown

It was examined whether the present site classification method, and especially its applicability to site productivity estimation, could be improved in upland Scots pine (Pinus sylvestris L.) forests in Southern Finland by developing a classification key based on Two-way Indicator Species Analysis (TWINSPAN), and/or by inclusion of soil texture, stoniness and the humus layer depth more closely in the classification method. TWINSPAN clusters (TW) explained 71%, and forest site types (FST) 64% of the variation in site index (SI) (H₁₀₀). When soil texture (TEXT) was added to the regression model, the explanatory power increased to 82% (SI = TW + TW * TEXT) and to 80% (SI = FST + FST * TEXT), respectively. Soil texture alone explained 69% of the variation in site index. The influence of stoniness on site index was significant (P <0.05) on sorted medium sand soils and on medium and fine sand moraine soils. The thickness of the humus layer (2–6 cm) was not significantly (P=0.1) related to site index.

It is suggested that the proposed TWINSPAN classification cannot replace the present forest site type system in Scots pine stands in Southern Finland. However, the TWINSPAN key may be used to aid the identification of forest types. The observation of dominant soil texture within each forest type is recommended.

The PDF includes an abstract in Finnish.

• Nieppola, E-mail: jn@mm.unknown

The matric potential and unsaturated hydraulic conductivity of peat-based growth media in containers was measured continuously as a function of drying. The particle size distribution and the water retention characteristics of the media were determined from parallel samples. The growth media used were a light, coarse graded Sphagnum peat, a medium graded Sphagnum peat and a mixture of a perlite and the medium graded Sphagnum peat. Containers of two types were packed with the media and allowed to evaporate from saturation. Matric potential was measured automatically using tensiometers during drying.

In both container types, the matric potential of the media was similar down to 10 kPa at each of the three levels measured during drying. Further drying resulted in a large matric potential gradient between the upper and the middle levels. During drying, there was also clear shrinkage of the media. When the matric potential at the upper level reached ca. -80 kPa, the decrease in height of the media was 5–23 %. The estimated hydraulic conductivity of the media during drying was rather similar. The hydraulic conductivity of the peat-perlite mixture was, however, slightly lower than that of the pure peat media. The hydraulic conductivity decreased linearly on a log-log-scale from ca. 10^-5 to less than 10^-10 m/s as the matric potential decreased from -3 to -60 kPa. The hydraulic conductivity of the media was comparable to coarse sand at matric potentials below -10 kPa. The decrease in hydraulic conductivity during drying and the possible weakening of soil-root contact due to shrinkage may considerably affect the availability of water to plants.
The PDF includes an abstract in Finnish.

• Heiskanen, E-mail: jh@mm.unknown