Articles containing the keyword 'water'

A new approach for modelling plant growth using the software AMAPpara is presented. This software takes into consideration knowledge about plant architecture which has been accumulated at the Plant Modelling Unit of CIRAD for several years, and introduces physiological concepts in order to simulate the dynamic functioning of trees. The plant is considered as a serial connection of vegetative organs which conduct water from the roots to the leaves. Another simple description of the plant as a network of parallel pipes is also presented which allows an analytical formulation of growth to be written. This recurring formula is used for very simple architectures and is useful to understand the role of each organ in water transport and assimilate production. Growth simulations are presented which show the influence of modifications in architecture on plant development.

• de Reffye, E-mail: pd@mm.unknown
• Barthélémy, E-mail: db@mm.unknown
• Blaise, E-mail: fb@mm.unknown
• Fourcaud, E-mail: tf@mm.unknown
• Houllier, E-mail: fh@mm.unknown

The model HYDRA, which simulates water flow in the branched tree architecture, is characterized. Empirical studies of the last decades give strong evidence for a close structure-function linkage in the case of tree water flow. Like stomatal regulation, spatial patterns of leaf specific conductivity can be regarded as a strategy counteracting conductivity losses, which may arise under drought. Branching-oriented water flow simulation may help to understand how damaging and compensating mechanisms interact within the hydraulic network of trees. Furthermore, a coupling of hydraulic to morphological modelling is a prerequisite if water flow shall be linked to other processes. Basic assumptions of the tree water flow model HYDRA are mass conservation, Darcy's law and the spatial homogeneity of capacitance and axial conductivity. Soil water potential is given as a one-sided border condition. Water flow is driven by transpiration. For unbranched regions these principles are condensed to a nonlinear diffusion equation, which serves as a continuous reference for the discrete method tailored to the specific features of the hydraulic network. The mathematical derivation and model tests indicate that the realization of the basic assumptions is reproducible and sufficiently exact. Moreover, structure and function are coupled in a flexible and computationally efficient manner. Thus, HYDRA may serve as a tool for the comparative study of different tree architectures in terms of hydraulic function.

• Früh, E-mail: tf@mm.unknown

The aim of the study was to compare the behaviour of three selected provenances of Eucalyptus microtheca F. Muell. that were likely to respond differently to drought. For this purpose, we studied the effects of vapour pressure deficit and soil water content on leaf water potential in an irrigated plantation in Bura, eastern Kenya.

An international provenance trial of Eucalyptus microtheca, established as a part of Finnida-supported Bura Forestry Research Project in eastern Kenya in 1984 was used as a plant material in the study. The eastern provenance showed generally the lowest leaf water potential on a daily basis. Statistically significant differences in the daily leaf water potential fluctuations were detected. The eastern provenance exhibited the greatest and the northern one the smallest values. The minimum daily leaf water potential of the provenances responded well to changes in gravimetric soil water content, the western provenance being the most sensitive one. The relationship of the observed results and annual rainfall distribution in the geographic regions of the studied provenances is discussed.

• Tuomela, E-mail: kt@mm.unknown
• Kanninen, E-mail: mk@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

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

Two-year-old containerized Scots pine (Pinus sylvestris L.) seedlings, raised under different fertilization and watering regimes, were subjected to feeding preference tests with pine weevils (Hylobius abietis L.) in a bioassay. In the tests carried out with pairs of seedlings, the weevil preferred water-stressed seedlings to well-watered ones. In the case of well-watered seedlings, the weevil caused significantly more damage to NPK-fertilized seedlings than those given pure PK fertilization, or no fertilization at all. It is apparent that PK fertilization reduces, and water stress increases seedling susceptibility to weevil damage. The results support findings from field trials that water stress (planting shock) predisposes seedlings to weevil damage. Weevil resistance is discussed with respect to fertilization and water stress as determinants of seedling quality.

The PDF includes an abstract in Finnish.

• Selander, E-mail: js@mm.unknown
• Immonen, E-mail: ai@mm.unknown

The matrix potential, measured with tensiometers, and its effect on the soil air-water ratio were examined during the production of bare-rooted Scots pine (Pinus sylvestris L.) seedlings in nursery fields. Soil water potential was monitored during the growing season of 1983 at three nurseries in Finland, and from fields growing various seedling types at depths of 10 and 20 cm. In 1986, soil core samples were collected in order to assess the water desorption characteristics of the soil. In addition, the effect of polypropylene gauze covering (Agryl P 17) on the soil water potential was examined during the growing season of 1985 at two nurseries in Finland at depths of 5, 10 and 15 cm.

The soil water potential was relatively high in all the fields studied. In fields growing one- and two-year-old seedlings, the median potential was higher than -10 kPa. The potential did not fall below the limit of the measured scale (ca. -85 kPa) of the tensiometers. Soil aeriation may have been periodically insufficient in the rooting zone, as a result of high water content. The favourable water potential is below -5 to – 6 kPa. The gauze covering slightly (1–4 kPa) increased the soil water potential, an effect which could be harmful if the soil air space is low. During the second growing season, the soil water potential was lower in the fields covered by the gauze during the first year than in the fields without the covering.

The PDF includes an abstract in English.

• Heiskanen, E-mail: jh@mm.unknown
• Raitio, E-mail: hr@mm.unknown

Five ploughed research areas from Finnish Norther Karelia were selected for comparison studies of plough ridges and untouched soil. Measurements were made at a depth of 10 cm in sample plots on both mineral and paludified mineral soil and peatland parts of these areas. In summer 1987 daily soil water matric potential was measured using tensiometers, and volumetric soil moisture content and density were determined from soil samples at two dates during the summer. Water characteristics of the core samples were also determined. On paludified mineral and peat soils the water table depth from the soil surface was measured.

The results indicated that in plough ridges matric potential was lowest. Plough ridges were also seen to dry and wet faster and to a greater degree than untouched soils. In untouched soils, soil water relations and aeration were not affected by the distance to the furrow. The effect of the plough ridge was smallest on peatland, where there was a good capillary connection from plough ridge to the ground water, if the ditches were not very effective. The soil in the ridges did not dry too much to restrict seedling growth. The untouched surface soil in poorly drained peat and paludified minear soil was, at least in a rainy growing season, often and also for long times so wet that 10% minimum air space required for good seedling root growth was not available.

The PDF includes an abstract in English.

• Mannerkoski, E-mail: hm@mm.unknown
• Möttönen, E-mail: vm@mm.unknown

The structure of 20 Scots pine (Pinus sylvestris L.) trees was analysed as a water transport system. There is a tight linear regression between the cross-sectional area of the stem at the height of its lowest living branch and the cross-sectional area of its coarse roots, between the cross-sectional area of the stem at the height of its lowest living branch and the total cross-sectional area of its branches, and between the cross-sectional area of the base of a branch and the total cross-sectional area of subsidiary branches of that branch. The capacity of successive organs, measured as cross-sectional areas, to transport water was thus found to be regular within a tree.

The PDF includes an abstract in Finnish.

• Hari, E-mail: ph@mm.unknown
• Heikinheimo, E-mail: ph@mm.unknown
• Kaipiainen, E-mail: lk@mm.unknown
• Korpilahti, E-mail: eeva.korpilahti@luke.fi
• Mäkelä, E-mail: am@mm.unknown
• Samela, E-mail: js@mm.unknown

The study discusses the amplitude of the simultaneous groundwater table fluctuations in different parts of pine mires, and factors influencing it. The assumption generally used in hydrological computations that the simultaneous vertical fluctuation in the groundwater table in different parts of mires are equal does not hold good in detail. Numerous cases were detected where the fluctuation at one place did not correspond to that at another site to a statistically significant degree. The main reason for the unequal fluctuation at the different sites seems to be the difference in the microtopography and in the hydraulic conductivity between the sites.

The PDF includes a summary in Finnish.

• Kurimo, E-mail: hk@mm.unknown

Altitude fluctuation of mire surface proportional to that of the groundwater table is presented for three virgin pine mires in Eastern Finland during the growing season 1982. The average amplitude of the surface fluctuation was found to be dependent on the period representing a certain type of weather, being limited to a certain maximum. The average amplitude of the surface fluctuation ranged from 18 to 45 mm; each of the mires followed a fluctuation scale of its own.

The daily fluctuation rates were low, generally 0.5–1 mm. No sudden fluctuation peaks occurred. Regularities in the surface fluctuation were caused by the duration of the period representing continuous sinking or rise of the groundwater table, and magnitude of it. The daily rate of the surface fluctuation related to that of the groundwater table was smaller in the beginning of such period than at the end of the same period. The one-directional rise or sinking of the altitude of the mire surface according to the groundwater table fluctuation is responsible for the autocorrelation of the long-term regression data.

The PDF includes a summary in Finnish.

• Kurimo, E-mail: hk@mm.unknown

The present study deals with the effect of forest drainage on some quality factors of brook waters. Under study were several brooks in the basin of the Kiiminkijoki River as well as its main tributary, the Nuorittajoki River. These are located in Northern Finland and belong to the international water program Project Aqua.

The following values were determined for the water samples: pH, electric conductivity, colour, concentration of suspended solids., NO₂, NO₃, and NH₄ nitrogen concentrations, dissolved and total phosphorus, and Ca, Mg, K and Fe concentrations. Water quality in the brooks was monitored prior to and after ditching. A statistically significant change was noted in colour, in the concentration of suspended solids, in the NH₄ concentration and in some brooks also in the pH value and in the total phosphorus, K, and Fe concentrations.

The PDF includes a summary in English.

• Hynninen, E-mail: ph@mm.unknown
• Sepponen, E-mail: ps@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

In 1975 the roundwood transport in Finland, which was mostly floated in the inland waters, accounted for 45% of the total transport performance and for 25% of the total transport volume. The paper describes the Finnish inland waterway fleet in 1975. The information was collected from the material of navigation inspectors who yearly inspect the seaworthiness of the merchant ships. The number of inspected vessels was 778. Of those 495 were tugs, 118 passenger boats, 71 warping boats, and the others totalled 94. The average power of tugs was 65 kW and that of warping boats 16 kW.

The PDF includes a summary in Finnish and French.

• Roitto, E-mail: yr@mm.unknown

The photosynthetic rate of Pleurosium schreberi (Willd.), Hylocomnium splendens (Hedw.) and Dicranum undulatum (Sw.) grown in plastic containers was monitored with infrared gas analyser in open air under natural weather conditions. It proved that the photosynthetic rate of wet moss cushions was satisfactorily predicted by temperature and light intensity. In dry moss cushions this kind of model gave too high an estimate for photosynthetic rate. Water requirements of each moss species were found to be moderate, and water content of moss cushions limited photosynthetic rate only under serious water deficiency.

The PDF includes a summary in Finnish.

• Kellomäki, E-mail: sk@mm.unknown
• Hari, E-mail: ph@mm.unknown

The paper describes the results obtained from an investigation into the effect of ditch spacing, ditch depth and furrowing on ground water table and on development of a Scots pine (Pinus sylvestris L.) plantation on open small-sedge bog in Central Finland (60° 50’ N; 24° 20’ E), drained in 1967. The area was planted in 1968 with 2+1 Scots pine transplants, and fertilized with Y fertilizer for peat soils. The seedlings were measured in 1972.

The depth of the ground water table was greater, the narrower the ditch spacing. The water furrows shortened the duration of the high ground water and lowered the ground water table particularly in the case of ineffective drainage. The narrower the ditch spacing within the blocks, the higher were the young trees. On the other hand, the differences in the height of the trees between the ditch spacings were eliminated by the effect of the furrows.

The PDF includes a summary in English.

• Päivänen, E-mail: jp@mm.unknown

The significance of water budget in June and July for forest and peatland vegetation, and consequent effects on fauna, climate and agriculture has been studied.

In June, the difference between evaporation and precipitation is greater than it is later in the summer. North of the line zero difference of evaporation and precipitation, coinciding with a line of sharp change in forest vegetation, the uppermost part of podsol remains wet throughout the summer. During July, the line of zero difference moves from north to south over the greater part of Finland, run-off being minute and podsol at the driest in this month. This line, indicating the length of the period with evaporation greater than precipitation and causing a sharp change in forest vegetation, in frequency of peatlands, amount of growing stock productive capacity of forests etc. This line is significant also for cultivation: because of the lower evaporation north of this line, night temperature below the freezing point often appear in summer.

The PDF includes a summary in English.

• Solantie, E-mail: rs@mm.unknown

The paper describes the results obtained from an investigation into the effect of thinning of different intensity and fertilization on the depth and water equivalent of the snow cover as well as on the depth of the soil frost in a young Scots pine (Pinus sylvestris L.) stand growing on drained peatland in Central Finland. Thinnings and fertilization was carried out in 1968, and the snow cover was followed in the winters 1970/71 and 1971/72.

Only extremely heavy thinnings (60% of the volume) seemed to increase the depth and water equivalent of the snow cover. The indirect effect of fertilization on the snow cover was insignificant. In the clear-cut sample plot of the study, soil frost was either not found at all or the depths of the frozen soil layer was smaller than in the other plots. When deciding the silvicultural measures to be taken in the case of tree stands growing on drained peatlands, there seems to be reason to avoid radical thinnings. Otherwise, the favourable influence of the trees on a site on its water relationships will be diminished.

The PDF includes a summary in English.

• Päivänen, E-mail: jp@mm.unknown

Scots pine (Pinus sylvestris L.) seedlings were stored for five days in an ordinary wood shed. One half of the seedlings were planted out directly, and another half after soaking the roots of the seedlings for 3–6 hours in water to compensate the possible water deficit developed. According to the results of the experiment, the effect of watering was extremely small. The difference observed, which was in favour of the trees that had been watered during storage, was discernible only in the needle length and in the number of lateral buds; in mortality or in the growth of the seedlings no difference could be observed.

The PDF includes a summary in English.

• Räsänen, E-mail: pr@mm.unknown
• Hiltunen, E-mail: mh@mm.unknown

The aim of the present study was to increase the knowledge of the anaerobic conditions prevailing in virgin peat soils of different kinds, and on the fluctuation of the aerobic limit. Silver rod method was used to indicate anaerobic conditions and to locate the aerobic limit. The material included 18 peatland sample plots on treeless bogs, in pine bogs and in spruce swamps in Southern Finland. Observations of the discoloration of the silver rods and measurements of ground water level were made from 8 June to 13 August 1968.

The results show that the location of the aerobic limit is dependent of the depth of the ground water table, and usually lies 5–15 cm above the ground water table. Down to 10–20 cm below the aerobic limit, where it reaches maximum, the rate of decomposition of sulfurous organic matter is positively correlated with the distance from the aerobic limit. Deeper it gradually decreases, and in the depth of 25–35 cm no hydrogen sulphide seems to be released.

In the forested peatland types the volume of the growing stock and the increment were dependent on the depth of the aerobic limit only when nutrient content and pH of the peat was more or less constant. Where the aerobic limit was close to the ground surface but the nutrient contents were relatively high, the volume of the growing stock may be comparatively high. Birch (Betula sp.), better than the conifers, is able to stand conditions poor in oxygen. The growing stock was poor in sites where the aerobic limit was near the ground surface, but the nitrogen and phosphorus contents were high, or vice versa. Consequently, aerobic limit is of great importance as an indicator of site quality.

The PDF includes a summary in English.

• Lähde, E-mail: el@mm.unknown

The aim of this study was to investigate how the weight loss and water content of cold stored plants depend on the storage conditions, and if there is a clear connection between these factors and the field survival of the planting stock. The experiments were carried out in a climate chamber at about +2°C and at three moisture levels (about 70, 85, and 95%) from November 1968 to May 1969. Three-year-old seedlings of Scots pine (Pinus sylvestris L.) average length 127 mm, diameter 3.5 mm and the top/root-ratio of fresh weight 1.93, were stored in open and sealed plastic bags. In addition, a transpiration retardant (Silvaplast) was used. The plastic bags (10 plants each) were weighted every 4. week. The remaining 270 seedlings were planted out and inspected after one growing season.

Although the experiment was made in a small scale, the results showed clearly that plant mortality, varying between 3 and 97%, was due to the storage conditions. The weight loss ranged between 2 and 50%, and the correlation between the weight loss and the mortality in the field was high. The water content of the seedlings was about 61%. The correlation between water content and survival was very high. Thus, the determination of weight loss or water content could be a useful method in observing the changes of water balance of the seedling stock during winter-storage. Further investigations are needed to show the tolerable rate of drying out for different sorts of plants. The Silvaplast-treatment had no visible effect either on the drying out or on the field survival.

The PDF includes a summary in English.

• Långström, E-mail: bl@mm.unknown

The purpose of forestry has hitherto been seen mainly as economic conservation, i.e. the use and management of timber resources on a sustainable yield basis. Along with the rising standard of living, however, amenity values of the environment will become more appreciated, which means that forestry and forest industries will be concerned with conservation of immaterial resources of nature as well. Since inland lakes cover some 10% of the surface area of Finland, and forests occupy more than 70% of the land area, forests and lakes are essential constituents of the Finnish environment during both work and leisure.

The main task of the pulp and paper industry in conservation is the control of water pollution. Today some 10% of Finnish lakes are polluted. Pulp and paper industries contribute 75% of the total waste water load of the Finnish lakes. Increasing water pollution can be prevented by improved processing technology, waste water treatment, and economic use of industrial wastes. Thus, the waste water load of the lakes has not increased in the last 10 years, despite doubling of pulp and paper production. According to the prognoses, by the year 2000 the waste water load from pulp and paper industries will be reduced to one half or one fourth of the present level although the capacity will still be increasing.

In forest management more emphasis should be paid on the aesthetic and recreational values of forests. Along with increasing leisure the need for recreational areas is growing. Scenic and recreational aspects must be considered in the management of industrial forests, too. With wise management, high timber yield is compatible with the maintenance of an enjoyable environment. Good silviculture takes account of timber production, wildlife management and landscape architecture simultaneously. National forestry development programs must be based on the principle of the multiple use of forests.

The PDF includes a summary in English.

• Mikola, E-mail: pm@mm.unknown

This study estimates the supply of soil water required for the annual and total production of energy material by the biomass of 32-year-old plantation of red pine, Pinus resinosa Ait. in Wisconsin, the United States.

The supply of transpiration water was determined as the sum of summer precipitation, winter stored water, and condensed vapor, minus gravitational discharge and evaporation of intercepted rainfall. On the average, the 1,20 m root zone of coarse sandy soils of central Wisconsin receives 2,750 M.T. of water per hectare. During the 32nd year of plantation growth, the increment biomass, including 43% of merchantable timber, was 10,100 kg/ha, or 162 x 105 kcal/g. At this time of the culminating growth, the production of 1 kg of wood material consumed 272 kg of water. The corresponding transpiration coefficient 0,37% is near the maximum for the ecosystem of hard pines – sandy soils of glacial outwash with field capacity between 7 and 9%. On the weight basis, the annual leaf fall constituted 32% of the biomass and over 80% of merchantable timber.

The entire supply of water of 96,000 M.T./ha produces in 32 years 211,112 kg of total dry matter at a rate of 1 kg of wood per 455 kg of water, with corresponding transpiration coefficient of 0,22%. The evapogravitational losses during the early stages of the stand’s growth decreased the water utilization efficiency of trees about 40%.

The information obtained permitted to outline several hydrological relationships pertinent to forest culture, namely: maximum rate of forest growth as delineated by the supply of available transpiration water; content of available moisture in soils of high tension capacity; contribution to soil water rendered by natural subirrigation and condensation of athmospehric vapor; growth depressing effect of weeds.

The PDF includes a summary in Finnish.

• Wilde, E-mail: sw@mm.unknown

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

Floating channels of Northern Finland have been unable to fulfill all the needs of wood transportation of the area. This presentation presents diferent ways to improve the efficiency of floating by improving working methods and the channels, and thus decreasing costs of wood transportation.

• Kivelä, E-mail: ak@mm.unknown

Silva Fennica issue 42 includes presentations held in professional development courses, arranged for foresters working in public administration in 1936. The presentations focus on practical issues in forest management and administration, especially in regional level. The education was arranged by Forest Service

This presentation describes the effects of draining of peatlands on water management in the peatland and the surrounding area.

• Metsänheimo, E-mail: um@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 the investigation was to obtain by snow and soil frost observations sufficient material for determination of regional springtime snow and soil frost values, because the water equivalent of snow and the frost depth affect runoff. The present paper elaborates a method by which the observations along a survey line can be corrected to be valid for a basin. Along the line 50 measurement points were arranged at specific intervals. Snow depth was recorded at each point, and snow density and frost depth at every fifth point. The terrain was studied along the line and the terrain of the survey points were classified in eight classes depending on the vegetation. The classes ranged from cultivated lands and open bogs to wooded areas according to volume of the growing stock and tree species composition.

The mean snow depth was 51.9 cm and mean snow density 0.235 g/m². Water equivalent of snow in class 4 terrain (forest with small growing stock) was 30% higher than in class 8 (forest with high growing stock). An ample stand increases evaporation in wintertime. The difference can be partly caused by the different accumulation of snow in the different types of stands.

Soil type was not found to have any distinct influence on the frost depth in the present material. On cultivated lands the soil frost clearly penetrates to greater depth than in the forest. The growing stock of wooded areas influences the snow depth

The PDF includes a summary in English.

• Mustonen, E-mail: sm@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

Result of a survey of soils supporting forest plantations in Wisconsin in the United States indicated a close correlation between the levels of fertility of non-phreatic, coarse-textured soils and the growth of red pine (Pinus resinosa Roezl) stands aged from 15 to 32. This relationship, however was not observed in plantations established on deep-gley soils, underlain at a depth of 3–9 fl by ground water.

The survey encountered 20 red pine plantations on soils underlain by a deep ground water table accessible to tree roots thorough their contact with gley horizon or with extended capillary fringe. The average growth of the stands was 80 cubic feet/acre (5.6 m³/ha) at the age of 22 years. Thus, mensuration analysis suggested that the soils are the choice grounds for forestry enterprise. However, the analysis of soil samples showed that in many instances the soils are extremely low in mineral colloids, organic matter and nutrients. Many of the sites would be regarded as critically deficient in nitrogen, phosphorus and potassium.

The following hypothesis are suggested to explain this discrepancy:

a) The moisture content of coarse-textured non-phreatic soils remain near the wilting point during a large apart of the growing season with subsequent reduction of transpiration and uptake of nutrients. If a capillary fringe provides a supply of water for the root system, trees may derive an adequate supply of salts and exchangeable ions from comparatively infertile substrata.

b) The suitably located ground water provides adequate aeration of the surface soil layers which is not impeded by capillary fringe, increasing activity of mycorrhiza, and a mycotrophic uptake of nutrients from unweathered minerals.

c) The above effects of natural subirrigation should change the concept of soil fertility based on mere chemical analysis. The time during which the roots are engaged in active absorption appears to be of equal importance as the concentration of nutrients in available form.

The PDF includes a summary in Finnish.

• Wilde, E-mail: sw@mm.unknown
• Iyer, E-mail: ji@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

In Finland roundwood is floated either privately or co-operatively. In the later, a co-operative floating association is established to operate floating. The association is compulsory association of those enterprises who want to have wood floated along the floating routes of the area. It is favoured when the number of enterprises and the wood to be floated is large. In addition, costs are lower than in private floating.

Floating in Lake Saimaa area in Central Finland can be divided into Iso-Saimaa, where floating is private, and into Saimaa Water System, where floating is operated by a co-operative floating association. It has been suggested that adoption of co-operative floating in Iso-Saimaa would be to the common interest. This study aimed at finding out if co-operative floating influences the transport costs, and if co-operative floating increases competition of roundwood by forest industry companies.

According to the study, the costs of most enterprises would decrease. The total decrease in costs would amount to 65 million Finnish marks annually, about 20% less than the present costs. The change of organization would not alter the competitive relationship in buying roundwood. On the other hand, it would seem that co-operative floating would be less flexible than private floating. The management of a large organization, whose effective operation time would cover only a part of the year, would meet with some difficulties. Also, co-operative floating would reduce competition among enterprises.

The PDF includes a summary in English.

• Roitto, E-mail: yr@mm.unknown

This paper aims at investigating which factors, in the point of view of the entrepreneur, define the choice of long-distance transport either as floating in bundles, steamship transport or barge transport in the waterway system of Lake Saimaa in 1950s. It defines the usage, kind of fleet, operation and costs of the abovesaid modes of transport. The investigation is mainly based on statistics of Enso-Gutzeit Oyj and the fuel office of the Finnish State Railways.

Location of the industrial enterprise sets the limits for use of the different modes of transport of roundwood. Previous decisions can influence the future choices, for instance, the capital the company has earler invested on the transportation system. Also, the type and amount of timber acquired by the company, transportation distance, time, and means of transport affect the choice of mode of transport. Those factors that direct decision-making, often lead the entrepreneur to stick to the chosen mode of transport.

Floating becomes the more inexpensive the larger the scale of operation is, and if the timber assortment is suitable for floating and water storage. For instance, dry wood is an asset for a wood export agency, and their sales have often time pressures, which rules floating out of their choices. Transportation in vessels has decreased to 4% of all roundwood haulage, but has its function as a supplementary way of transport.

The PDF includes a summary in German.

• Roitto, E-mail: yr@mm.unknown

Central Association of Finnish Forest Industries decided in 1953 to begin collecting annual statistics of timber transportation of its members. The survey of members covers almost 97% of the timber transportations of the member companies, which have production over 1,000 cu ft. In all 79 companies answered the survey. Their total timber transportation was 166,4 million cu ft in 1952.

The long-distance transportation of saw logs by horse transport directly to the mill or other such location was 1,297 cu ft, by truck transport 42,644 cu ft, by rail transport 6,707 cu ft, and by water transport 115,789 cu ft. The average transportation distance was for horse transport 2.4 km, truck transport 27 km, rail transport 224 km and water transport 209 km.

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

• Lindfors, E-mail: jl@mm.unknown

About 17.5% of forest lands of Finland is situated around the river and lake system of Lake Saimaa. Furthermore, the growth of the forests  of the area correspond about 25% of the total growth of forests in Finland. The watersystem is one of the most important portages of roundwood in the country. It consists 11,000 km of floating channels, 2,000 km of which suit for floating in bundles. Annually 30-35 million cu ft of saw logs, 7 million cu ft of veneer timber and 2,5-3 million cu ft of pulp wood is floated in the area.

Even if the water system at present still suits well for floating, there are many opportunities for development, which would improve its competitiveness against other modes of transport. Several different sites where building of floating channels or improving the floatways are needed are described in the article.

The PDF includes a summary in German.

• Roitto, E-mail: wr@mm.unknown

In the present investigation, the problems connected to demand of firewood are dealt with by studying the fuel markets of the three biggest towns in Finland – Helsinki, Turku and Tampere as well as those of Vaasa. The purpose of the investigation was to study the firewood supply areas in two time periods, in 1933-1939 and in 1945-1947, after the Second World War.

Railway and shipping were the most important ways for transporting firewood in 1933-1939. Towards the end of the period, road transport increased especially in Turku and in Vaasa. In 1945-47 almost 90% of the firewood transported to Helsinki, 60% to Tampere and Turku, and over 50% of the firewood transpors to Vaasa were carried by rail. One factor supporting rail transport was that the tariff policy of the State Railways gave preference to firewood transports.

The supply areas increased markedly from 1933-1939 to 1945-1947. Supply of firewood near the towns in the southern, southwestern and western parts of the country was small. Also, pulp industry began to use small-sized timber in 1930s, which increased competition of the wood. Coal and coke began to replace firewood in the 30s, but their use decreased during and after the war due to supply shortage.

The PDF includes a summary in English.

• Holopainen, E-mail: vh@mm.unknown

In Finland, transportation of wood by vessels has decreased, but is still an important mode of transport especially for firewood. In 1941-1947, nearly 25% of the firewood procured by the State Fuel Board was transported by vessels. This investigation concentrates on loading of wood into barges, since the share of wages of total expenses is greatest in this phase. The loading work amounts to nearly 40% of the total wages.

Two methods of loading barges are used in Finland: loading from the shore and truck loading. This study concentrates on the more common method, loading from the shore. A time study was conducted on the different stages of loading and piling wood into barges, most of which is done by hand. Most time-consuming part of the work is transporting the logs to the barge with a wheelbarrow, comprising over 40% of the working time. Time required for loading firewood is almost twice as much as loading pulp wood. Recommendations for loading places and organization of work are given in the article to improve the efficiency of the work.

The PDF includes a summary in English.

• Heiskanen, E-mail: vh@mm.unknown

The tree canopy adsorbs part of the rainfall falling on a forest, therefore only part of it reaches the soil. This report presents results concerning interception of precipitation and groundwater level in forests of varying canopy cover. The study belongs to a larger survey on afforestation of drained treeless bogs. The rainfall was measured daily in the open fields and in the adjacent forests. The forests, mainly Norway spruce (Picea abies (L.) Karst.) dominated, were divided by the canopy cover into five classes from over dense to sparsely stocked.

The results show that in a dense, tall Norway spruce stand, light rainfall can almost entirely be adsorbed by the canopy. The heavier the rainfall, the larger proportion of it reaches the ground. Only 30% of a 5 mm rainfall reaches the ground, while 80% of a 20 mm rainfall reaches the ground. Interception of precipitation decreases gradually when the density of the forest decreases. Canopy of Scots pine (Pinus sylvestris L.) and birch (Betula sp.) stands of corresponding density adsorb less rainfall than Norway spruce canopy. Groundwater level was higher in treeless areas than in areas covered with forest. Widescale clear cuttings should, therefore, be considered carefully in forest areas that are prone to become peaty.

• Lukkala, E-mail: ol@mm.unknown

Water and amount of light are the most important growth factors and the article discusses their relationship. It is knows that the more space is needed by a tree the worse the site is. The number of stems varies between tree species. Common understanding is that amount of light is decisive to self-thinning and regeneration of a stand. On a good site the adequacy of water may substitute the lack of light. However, the fertility of soil and moisture content is more important than light.

The question of the importance of light, soil fertility and water content, as well as their relationship is important when optimizing the forest management.       

The PDF contains a summary in Finnish.  

• Aaltonen, E-mail: va@mm.unknown

The article presents the observations made on peatland “Savonneva” in summer 1929 in commune Pulkkila, north-west Finland. The study concentrates on the relationship between groundwater level and growth of trees. The areas was first ditched in 1894, when a main ditch and a side ditch were dug. The ditches were repaired several times, last time a year before the study took place.    

Parts of the area has been taken for agricultural purposes, and other areas have been naturally afforested. The size and abundance of trees varies strongly because the drainage of the area has been uneven. Closer to the main ditch the forest grows better than further away. There is a clear line between the afforested and open areas.

It seems that the tree growth decreases faster with certain groundwater levels than if the groundwater level is deeper.  

The volume 34 of Acta Forestalia Fennica is a jubileum publication of professor Aimo Kaarlo Cajander.

• Kokkonen, E-mail: pk@mm.unknown

The article presents some basic elements of soil frost and its occurrence.  The data contains observations from different regions and soil types in Finland. Different forms of soil frost and factors affecting its formulation are discussed. 

• Kokkonen, E-mail: pk@mm.unknown

The data has been collected in the dry heathy forests in Harjavalta commune in south-west Finland and in Sodankylä commune in Lapland in summer time 1918 and 1919. The aim to the study was to find out how does the water consumption of the trees affect the moisture conditions of the soil and how they are linked to the regeneration of the forest.

Trees in one age class have a certain spatial distribution: the greater the distance between trees the older the trees and the smaller the distance, the younger the trees. This seem to rather be due to the development of the root system and the nutrition intake of a tree than the competition for light. The moisture content of the upper soil layers is higher in the open areas than in the closed canopy stands. Hence there are more seedlings growing in open areas.   However, it is not clear whether the results apply for other forest site types as well, and more research is needed.     

• Aaltonen, E-mail: va@mm.unknown

In this study we analyse how the ion concentrations in forest soil solution are determined by hydrological and biogeochemical processes. A dynamic mode ACIDIC was developed, including processes common to dynamic soil acidification models. The model treats one to eight interacting layers and simulates soil hydrology, transpiration, root water and nutrient uptake, cation exchange, dissolutions and reaction of Al hydroxides in solution, and the formation of carbonic acid and its dissociation products. It includes also a possibility to a simultaneous use of preferential and matrix flow paths, enabling the throughfall water to enter the deeper soil layers in macropores without first reacting with the upper layers. Three different combinations of routing the throughfall water via macro- and micropores through the soil profile is presented. The large vertical gradient in the observed total charge was simulated successfully. According to the simulations, gradient is mostly caused by differences in the intensity of water uptake, sulphate adsorption and organic anion retention at the various depths. The temporal variations in Ca and Mg concentrations were simulated fairly well in all soil layers. For H⁺, Al and K there were much more variation in the observed than in the simulated concentrations. Flow in macropores is a possible explanation for the apparent disequilibrium of the cation exchange for H⁺ ad K, as the solution H⁺ and K concentrations have great vertical gradients in soil. The amount of exchangeable H⁺ increased in O and E horizons and decreased in the Bs1 and Bs2 horizons, the net change in whole soil profile being a decrease. A large part of the decrease of the exchangeable H⁺ in the illuvial B horizon was caused by sulphate adsorption. The model produces soil water amounts and solution ion concentrations which are comparable to the measured values, and it can be used in both hydrological and chemical studies of soils.

• Kareinen, E-mail: tk@mm.unknown
• Nissinen, E-mail: an@mm.unknown
• Ilvesniemi, E-mail: hi@mm.unknown

Microcatchment water harvesting (MCWH) improved the survival and growth of planted trees on heavy soils in eastern Kenya five to six years after planting. In the best method, the cross-tied furrow microcatchment, the mean annual increment (MAI; based on the average biomass of living trees multiplied by tree density and survival) of the total and usable biomass of Prosopis juliflora (Sw.) DC. were 2,787 and 1,610 kg ha^-1 a^-1 respectively, when the initial tree density was 500 to 1,667 trees per hectare. Based on survival, the indigenous Acacia horrida Span., A. mellifera (Vahl) Benth. and A. zanzibarica (S. Moore) Taub. were the most suitable species for planting using MCWH. When both survival and the yield were considered, a local seed source of P. Juliflora was superior to all other species. The MAI in MCWH was at best distinctly higher than that in the natural vegetation (163–307 and 66–111 kg ha^-1 a^-1 for total and usable biomass respectively); this cannot satisfy the fuelwood demand of concentrated populations, such as towns or irrigation schemes.

The density of seeds of woody species in the topsoil was 40.1 seeds/m² in the Acacia-Commiphora bushland and 12.6 seeds/m² in the zone between the bushland and the Tana riverine forest. Rehabilitation of woody vegetation using the soil seed bank alone proved difficult due to the lack of seeds of desirable species.

The regeneration and dynamics of woody vegetation were also studied both in cleared and undisturbed bushland. A sub-type of Acacia-Commiphora bushland was identified as Acacia reficiens bushland, in which the dominant Commiphora species is C. campestris. Most of the woody species did not have even-aged population but cohort structures that were skewed towards young individuals. The woody vegetation and the status of soil nutrients were estimated to recover in 15–20 years on Vertic Natrargid soils after total removal of above-ground vegetation.

• Kaarakka, E-mail: vk@mm.unknown

The aim of this study was to investigate the ecophysiological and morphological characteristics of two salt-tolerant tree species, Eucalyptus camaldulensis Dehn. and Combretum quadrangulare Kurz. A greenhouse experiment with different levels of NaCl salinity (0, 0.5, 1.0, 1.5, and 2.0%) was set up and the results were compared with those of a field study on non-saline and saline soils. The determination of optimum gas exchange and the development and evaluation of photosynthetic models with and without water deficit were also included in this study.

Morphological characteristics under saline conditions showed that shoot height and diameter growth, shoot internode length, root length/biomass, leaf width and length, leaf area, number and biomass, and shoot/root and leaf/root ratios decreased with salinity, while leaf thickness increased with salinity. More growth was allocated to the roots than to the leaf canopy. Ecophysiological studies in laboratory showed that photosynthesis, stomatal conductance and water potential decreased with salinity, while the CO₂ compensation point increased with salinity. Transpiration, dark respiration and photorespiration increased at low salinity but decreased at high salinity levels. In the field study, however, there were no significant differences in stomatal conductance and opening between saline and non-saline soils. Model predictions supported the results of the field measurements. Adaptation to salinity was reflected in an acclimatization of tree structure in the field study. There were both functioning and structural changes of seedlings in the greenhouse experiment

In terms of ecophysiological and morphological characteristics, E. Camaldulensis showed better salt tolerance than C. Quadragulare both in the greenhouse experiment and field study

The PDF includes a summary in Finnish.

• Luangjame, E-mail: jl@mm.unknown

Genetic variation in the physiological characteristics and biomass accumulation of Acacia mangium Willd. was studied in both field and laboratory conditions. Variation in the growth characteristics, foliar nutrient concentration, phyllode anatomy and stomatal frequency was analysed in 16 different origins under field conditions in Central Thailand. Family variation and heritability of growth and flowering frequency were calculated using 20 open-pollinated families at the age of 28 months. The effect of environmental factors on diameter growth in different provenances is also discussed.

Under laboratory conditions, such physiological characteristics as transpiration rate, leaf conductance and leaf water potential were measured at varying soil moisture conditions. The responses of photosynthesis, photorespiration and dark respiration as well as the CO₂ compensation point to temperature and irradiance were also investigated. All physiological characteristics indicated differences among provenances. An attempt was made to relate the results obtained in the laboratory to the growth performance in the field. Recommendations on provenance selection for the planting of A. mangium in Thailand are also given.

The PDF includes a summary in Finnish.

• Atipanumpai, E-mail: la@mm.unknown

Soil respiration readings are reported for three ameliorated peatland sites of different types, covering a period of four years, during which the sites were drained and treated with various fertilizers. Respiration is shown to increase exponentially with temperature, varying mostly in the range 100–500 mg CO² m^-2 h^-1. The changes in soil respiration followed those in surface temperature with a time-lag of approximately 3–3.5 hours. At one site, where the groundwater table dropped by about 0.5 m after ditching, soil respiration increased 2.5-fold within a few weeks, whereas at the other two sites both the fall in the groundwater table and the resultant changes in soil respiration were small.

The fertilizers tested were slow-dissolving PK, fast-dissolving PK, wood ash, slow-dissolving PK + urea, slow-dissolving PK + Nitroform (urea formaldehyde) and slow-dissolving PK + urea + a micro-element mixture. Application of fast-dissolving PK + urea led to a rapid increase in soil respiration at the site poorest in nutrients, and slow-dissolving PK to a slow increase in respiration. The greatest, steady increase of all was achieved by treatment with ash. At the sites with a higher natural nutrient content the application of fertilizers usually led to a decline in soil respiration lasting 1–2 years, after which the initial level was normally regained. Treatment with micro-elements caused an initial fall in soil respiration values in all three biotopes, followed by a pronounced increase.

The PDF includes a summary in Finnish.

• Silvola, E-mail: js@mm.unknown
• Välijoki, E-mail: jv@mm.unknown
• Aaltonen, E-mail: ha@mm.unknown

The applicability of operations research, database management systems and geographic information systems for decision-making in long-distance transport of wood in the Saimaa area in Central Finland were reviewed. Due to the complexity of the transport problem a geographic information system is the most applicable. However, investment in such a system for only long-distance transport decision-making is unjustified. A spatial database – heuristic programming system was developed. It was applied to studying the competitiveness and search for possible areas for rationalization of water transport in particular and long-distance transport in general. The system proved to be a useful aid in long-distance transport research. Also, with the increased use of computers for planning at the field level, a system similar to that described could be a powerful managerial aid.

The PDF includes a summary in Finnish.

• Pulkki, E-mail: rp@mm.unknown

The aims of the present study were to determine physical and physio-chemical properties of some Finnish forest tree nursery soils, and to examine relationships between these properties and the amount of organic matter in the soil.

The following soil tillage layer properties of 33 fields belonging to 8 forest tree nurseries were determined: soil particle size distribution, organic matter content, bulk density and density of solids, total pore space, soil water volume at potentials pF 2.0 and 4.2, available water content and air space at potential pF 2.0, active acidity, electrical conductivity index and cation exchange capacities at pH 4.5 and 8.0. The soil texture class of the tillage layer parent material was sand, only in a few cases did higher percentage of silt and clay indicate a morainic nature of parent material. The amount of organic material in the soils varied within wide limits, reflecting differences in amelioration policy between the single nurseries.

Relationships between the physical properties of the soil parent material and those related to fertility were in most cases strongly influenced by the amount of soil organic matter. Soil density values decreased as the organic matter content increased from 2 to 25%, giving rise to the increase in the total pore space. However, the amount of water held at potential pF 2.0 and the available water content did not increase with increasing organic matter content. This was due to the absence of the particle fraction in the sand. Nursery soil amelioration, involving in most cases a mixture of Sphagnum peat with sand, thus gives rise to an increase in the content of drainable water.

Cation exchange capacities were positively correlated with the organic matter content. However, the absolute number of exchange sites expressed as equivalents in the tillage layer did not increase in accordance with the increase in organic matter content due to the influence of the organic matter content upon the ratio of solids in the voids.

The PDF includes a summary in English.

• Westman, E-mail: cw@mm.unknown

The aim of this investigation was to examine the dependence of stand volume and increment on different growth factors on drained peatlands drained 20 years ago. Measurements were made in 1977-79 on 35 sample plots in Central Finland on relatively poor pine bogs with a thick peat layer.

It became evident that the stand volume, increment and radial growth and growth development are primarily functions of groundwater depth. Groundwater depth is dependent, in the first place, on ditch depth and ditch condition. With regard to the variation in ditch spacing (ca. 35-70 m) under examination, the effect of ditch spacing on the stand was insignificant. As a practical recommendation it was concluded that ditches should be kept deep enough (> 70 cm) in order to maintain undisturbed stand development.

The PDF includes a summary in English.

• Heikurainen, E-mail: lh@mm.unknown

The net photosynthetic rate per unit of foliage was studied in two-year old cuttings of Norway spruce (Picea abies (L.) H. Karst.), representing four clones, at varying temperature and soil moisture. The CO₂ compensation point (Γ), photorespiration, dark respiration, and water balance were also investigated. All these characteristics indicated differences among the clones. A correlation between CO₂ exchange and transpiration suggested that stomatal control determined at least a part of this variation during a favourable water balance. An inverse relationship existed between Γ and net photosynthetic rate, and the same curvilinear model explained this variation in unstressed as well as stressed plants at a given temperature. An increase in Γ seems to be a normal result of water stress, particularly at high temperature, indicating an increase in mesophyll resistance to CO₂ diffusion. This result was in agreement with calculated values of mesophyll resistance. It also supported our earlier conclusions about the significance of mesophyll resistance during water stress.

• Luukkanen, E-mail: ol@mm.unknown

In the experiment Scots pine (Pinus sylvestris L.) seedlings were transplanted out in the field. The effect of the treatments on gas metabolism and daily height increment were examined. The seedlings were 5-year old Scots pine plants growing in clay pots, covered with plastic bags. Transpiration and photosynthetic rates were monitored with open IRGA measuring system for a few days before being subjected to the treatments and for one month after. In addition, the daily amounts of transpired water and daily height increments were measured. A model for the potential rate of each metabolic process was constructed.

Planting and additional exposure had a strong and rather permanent effect on the self-regulation of the processes. This effect is very similar to that caused by water deficit. Exposure makes the disturbance more pronounced. Transpiration of the transplanted seedlings decreased in a few days after planting to less than half of the potential value and that of the exposed ones decreased to a quarter of the potential value. The daily amounts of photosynthesis decreased to half of the potential value. There was no recovery in photosynthesis during the whole monitoring period of four weeks. There was a slight recovery in transpiration about five weeks after transplanting.

Thus, the treatment probably generated stress conditions throughout the whole growing period, which is characterized by strong self-regulation of photosynthesis and transpiration, thus causing an essential decrease in the total amount of CO₂ fixed. The photosynthesis was depressed especially at elevated temperatures after planting, as during water deficit. Planting and additional exposure did not produce any detectable changes in the dependence of the growth rate on temperature or in the effect of self-regulation on height growth. On the other hand, the level of growth was decreased as a result of planting out.

The PDF includes a summary in Finnish.

• Hallman, E-mail: eh@mm.unknown
• Hari, E-mail: ph@mm.unknown
• Räsänen, E-mail: pr@mm.unknown
• Smolander, E-mail: hs@mm.unknown

The transport unit in roundwood towing on Lake Iso-Saimaa in Central Finland comprises a tug and a raft of bundled wood with a towline between them. There are several factors influencing the economic size of the transport unit in roundwood towing. These are changing with the enterprises and along with general developments. In this paper these factors or factor groups are seen from the point of view of the enterprise. The main question is to determine the most economic combination of tug and raft size.

From the point of view of the towing enterprises the unit costs of transport are the most decisive factor. Both the size of the raft as well as the power of the tug influence strongly the unit costs. As a long-term goal a raft of about 35,000 m³ and a tug of 550 kW or more is considered to be advisable. The width of channels and sounds then allow a free passage for rafts being 36–40 m wide.

The PDF includes a summary in Finnish and in French.

• Roitto, E-mail: yr@mm.unknown

The paper is a part of a larger study of the basic hydrologic properties of peat. This part of the study deals with the hydraulic conductivity and water retention capacity of peat and with their dependence on some of its structural properties. The data of the study was collected in Central Finland (61°50'N; 24°20'E) from drained peatlands. The limits of the quantitative range of variation in the hydraulic conductivity of peat can be put at 2.0 x 10^-6 and 1.1 x 1O^-2 cm/sec. The variation occurring in the hydraulic conductivity of peat is extremely large. At saturation peat contains 82–95 volume per cent of water. The bulk density of peat seemed to be the factor best able to explain its water retention capacity. The quantity of water which can be removed from a site by draining decreases with increasing bulk density in such a way that it, in the case of well decomposed peat (bulk density 0.20 g/cm³) is slightly less than one third of that for slightly decomposed peat (bulk density 0.05 g/cm³). Also, the possibilities to estimate the quantities of water superfluous, available and unavailable to the plant cover is discussed.

The PDF includes a summary in Finnish.

• Päivänen, E-mail: jp@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

This study was carried out in 1966 in the nursery at Hyytiälä, Korkeakoski Forest District, in Southern Finland. The influence of lifting date (two liftings), way of packing (two methods) and length of storage (one, three and six weeks) on the development of Scots pine (Pinus sylvestris L.), 2 + 1, during the four years following planting was assessed. On the seedlings stored for six weeks, the influence of compensating for the water deficit was also studied.

According to the results, the lifting carried out later, i.e. when the seedlings had already started growth, gave slightly better results than when seedlings were lifted earlier. No difference could be observed for seedlings stored for one week, but for the seedlings stored for three or six weeks, mortality in the lot lifted earlier was 6- to 7-fold that of the seedlings lifted later. The main reason for this was probably that the seedlings of the earlier lifting suffered from lack of water at the time of lifting.

The growth of the seedlings lifted earlier and stored for three weeks showed a decrease compared to those lifted later. For the seedlings stored for six weeks, on the other hand, faster growth was recorded for both the seedlings of the earlier and the later lifting in comparison with those stored for shorter times. Watering increased to some extent the growth of the seedlings stored for six weeks.

During the normal, one- and three-week storing periods, seedlings were well preserved when packed both in bundles and in polythene sacks. Three years after the planting the average mortality was about 10%. Effect of watering was large for those seedlings that had been longer in the storage.

The PDF includes a summary in English.

• Räsänen, E-mail: pr@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

The aim of the present study was to collect information on biological activity in the topmost 30 cm peat layer in certain natural and drained peatlands of different fertility, covered by different stands.

The results showed that if the ground water table in peatland sites is located in the immediate vicinity of the ground surface (about 5-10 cm in depth), conditions are reducing, and often even anaerobic, up to the ground surface. By means of drainage the aerobic limit can be dropped to a greater depth. This will occur because of the aerobic limit closely follows the fluctuation of the ground water table.

Although, by means of drainage, the aerobic limit can be lowered to more than 50 cm in depth, rains are followed by a rise of a ground water table and the aerobic limit; hereby a change from oxidizing to reducing conditions takes place. Only by keeping the ground water table and the aerobic limit constantly at the depth of more than 50 cm is it possible to obtain oxidizing conditions in the topmost 20-30 cm peat layer. The anaerobic conditions prevent the tree roots penetrating deeper in the peat.

In reducing conditions cellulose decomposition as well as carbon dioxide release from peat samples is slower than in oxidizing conditions. The rate of cellulose decomposition, however, is essentially dependent on the nitrogen content and the acidity of the peat.

• Lähde, E-mail: el@mm.unknown

• Nordin, pcSKOG, Grisslevägen 15, 227 32 Lund, Sweden https://orcid.org/0000-0002-2156-6615 E-mail: per.nordin@skogforsk.se
• Olofsson, Linnaeus University, Department of Forestry and Wood Technology, 351 95 Växjö, Sweden https://orcid.org/0000-0001-5844-6775 E-mail: erika.olofsson@lnu.se
• Hjelm, Swedish University of Agricultural Sciences, Southern Swedish Forest Research Centre, Box 190, 234 22 Lomma, Sweden https://orcid.org/0000-0002-6144-8250 E-mail: karin.hjelm@slu.se

In southern Lapland, 70% of drained peatland forests have a peat layer thickness of less than one metre. On these sites, the question is how the subsoil under the peat affects groundwater level and thus timber harvesting. The aim of this study was to investigate the effect of the peat layer (<1 m) and subsoil on the groundwater level and its variation during the growing season (non-frost) by modelling the factors affecting water level. In sandy soils, the groundwater level rose by 20 cm when the peat layer thickness increased from 20 to 70 cm. In silty soils the effect of the peat thickness on groundwater remained minor. When the subsoil was sand or coarser, the groundwater level was usually deeper than when it was silty or finer. The effect of stand volume (m^–3 ha^–1) on the groundwater level was rather weak albeit significant. The model explained a significant part of the groundwater surface variation, with a marginal coefficient of determination (R²) of 68%. It seems that the rutting of roads could be avoided in late summer if the precipitation is remarkably lower during that period, or if the subsoil is sandy with thin peat layer on top of it. Because the groundwater level affects the load-bearing capacity of timber-harvesting machinery, it is important to study this issue in more detail in the future.

• Hiltunen, Lapland University of Applied Sciences, Jokiväylä 11, FI-96300 Rovaniemi, Finland E-mail: oivah@student.uef.fi
• Hallikainen, Natural Resources Institute Finland, Ounasjoentie 6, FI-96300 Rovaniemi, Finland E-mail: ville.hallikainen@luke.fi
• Palander, The University of Eastern Finland, Faculty of Science, Forestry and Technology, P.O. Box 111, FI-80101 Joensuu, Finland https://orcid.org/0000-0002-9284-5443 E-mail: teijo.s.palander@uef.fi

Forest buffers beside surface water can mitigate negative effects of logging. To gain more information on buffer implementation in operational forestry, forest buffers were inventoried during 2018 on 174 harvested and site-prepared compartments traversed by or bordering streams, ditches and lakes in three regions across Sweden 2–4 years after clearcutting. Most of the inventoried stream and ditch reaches were ≤5 m wide. The water reaches were categorized as lakes (n = 16), natural streams (n = 50), modified streams (n = 21) or ditches (n = 87). Forest buffers with 100% shoreline coverage were present along all lake reaches and 55% and 10% of the natural or modified stream and ditch reaches, respectively. Buffers were absent beside 14% of the natural or modified stream reaches and 61% of the ditch reaches. Lake reaches had significantly wider buffers on average than ditch reaches and natural or modified stream reaches. The mean (SE) buffer widths beside lakes, natural or modified stream reaches and ditch reaches across all three regions and shoreline coverage classes were 12 (1.1), 6.6 (0.6) and 1.5 (0.5) m, respectively. The character of the local stream networks (natural or modified streams or ditches) containing each inventoried reach, were assessed using map information and the reaches´ field classifications. This illustrated the difficulty of judging a streams´ character based solely on field inspections of individual reaches on forest land where historic drainage activities have been performed. We recommend that also upstream and downstream conditions should be considered when planning environmental measures to protect surface water bodies.

• Ring, Skogforsk (The Forestry Research Institute of Sweden), Uppsala Science Park, 751 83 Uppsala, Sweden https://orcid.org/0000-0002-8962-9811 E-mail: eva.ring@skogforsk.se
• Johansson, Skogforsk (The Forestry Research Institute of Sweden), Uppsala Science Park, 751 83 Uppsala, Sweden E-mail: fredrik.johansson@skogforsk.se
• von Brömssen, Department of energy and technology, Division of applied statistics and mathematics, Swedish University of Agricultural Sciences, 750 07 Uppsala, Sweden https://orcid.org/0000-0002-1452-8696 E-mail: Claudia.von.Bromssen@slu.se
• Bergkvist, Mellanskog, Uppsala Science Park, Box 127, 751 04 Uppsala, Sweden E-mail: isabelle.bergkvist@mellanskog.se

We used a process-based hydrological model SUSI to improve guidelines for ditch network maintenance (DNM) operations on drained peatland forests. SUSI takes daily weather data, ditch depth, strip width, peat properties, and forest stand characteristics as input and calculates daily water table depth (WTD) at different distances from ditch. The study focuses on Scots pine (Pinus sylvestris L.) dominated stands which are the most common subjects of DNM. Based on a literature survey, and consideration of the tradeoffs between forest growth and detrimental environmental impacts, long term median July–August WTD of 0.35 m was chosen as a target WTD. The results showed that ditch depths required to reach such WTD depends strongly on climatic locations, stand volume, ditch spacing, and peat thickness and type. In typical ditch cleaning areas in Finland with parallel ditches placed about 40 m apart and tree stand volumes exceeding 45 m³ ha^–1, 0.3–0.8 m deep ditches were generally sufficient to lower WTD to the targeted depth of 0.35 m. These are significantly shallower ditch depths than generally recommended in operational forestry. The main collector ditch should be naturally somewhat deeper to permit water outflow. Our study brings a firmer basis on environmentally sound forestry on drained peatlands.

• Hökkä, Natural Resources Institute Finland (Luke), Natural resources, Latokartanonkaari 9, P.O. Box 2, FI-00791 Helsinki, Finland E-mail: hannu.hokka@luke.fi
• Laurén, University of Eastern Finland, Faculty of Science and Forestry, School of Forest Sciences, P.O. Box 111, FI-80101 Joensuu, Finland E-mail: ari.lauren@uef.fi
• Stenberg, Natural Resources Institute Finland (Luke), Natural resources, Latokartanonkaari 9, P.O. Box 2, FI-00791 Helsinki, Finland E-mail: leena.stenberg@luke.fi
• Launiainen, Natural Resources Institute Finland (Luke), Bioeconomy and environment, Latokartanonkaari 9, P.O. Box 2, FI-00791 Helsinki, Finland E-mail: samuli.launiainen@luke.fi
• Leppä, Natural Resources Institute Finland (Luke), Bioeconomy and environment, Latokartanonkaari 9, P.O. Box 2, FI-00791 Helsinki, Finland E-mail: kersti.leppa@luke.fi
• Nieminen, Natural Resources Institute Finland (Luke), Natural resources, Latokartanonkaari 9, P.O. Box 2, FI-00791 Helsinki, Finland E-mail: mika.nieminen@luke.fi

Scarification is a mechanical site preparation technique designed to create microsites that will favor the growth of planted tree seedlings after clearcutting. However, the positive growth response of black spruce (Picea mariana (Mill.) Britton, Sterns & Poggenb.) to scarification varies across different sites. We hypothesized that this was due to different forms of physiological stress induced by different climates or by the severity of competition from ericaceous shrubs. We thus compared the effects of scarification on black spruce needle gas exchange and other foliar properties, as well as on indices of soil water and nitrogen availability, in relatively warm-dry (Abitibi) vs. cool-humid (Côte-Nord) climates in the province of Québec (Canada). We found a similar positive effect of scarification on tree height in Abitibi and Côte-Nord. Scarification reduced soil moisture in both climatic regions, but increased soil N mineralization in Côte-Nord only. Accordingly, scarification increased the instantaneous water use efficiency in both climate regions, but decreased photosynthetic N use efficiency in Côte-Nord only. In both regions, we found a positive relationship between foliar δ¹⁸O and δ¹³C on scarified plots, providing further evidence that increased growth due to scarification depends on a decrease in stomatal conductance. We conclude that scarification increases total evapotranspiration of trees evenly across the east-to-west moisture gradient in the province of Québec, but also improves long-term soil nutritional quality in a cooler-humid climate.

• Wotherspoon, Département de biologie, Université de Sherbrooke, Sherbrooke, Québec, J1K 2R1, Canada E-mail: amy.wotherspoon@usherbrooke.ca
• Thiffault, Canadian Wood Fibre Centre, Canadian Forest Service, Natural Resources Canada, 1055 du. P.E.P.S., P.O. Box 10380, Québec, G1V 4C7, Canada E-mail: nelson.thiffault@canada.ca
• Bradley, Département de biologie, Université de Sherbrooke, Sherbrooke, Québec, J1K 2R1, Canada E-mail: robert.bradley@usherbrooke.ca

Physical soil properties have a marked influence on the quality of forest sites and on the preconditions for forest growth and management. In this study, water retention characteristics (WRC) and related physical soil properties in addition to vegetation coverage and tree stand data were studied at upland forest sites in Finland. Fixed and mixed models between soil and site characteristics were formed to estimate physical and hydrologic soil characteristics and the site quality with indirect co-varying variables. In the present data, the site quality index (H100) shows a high coefficient of determination in respect to the temperature sum. It is also related to soil fine fraction content, topsoil pH and water retention at field capacity. The thickness of the humus layer is predictable from the pH and cover of xeric and mesic plant species. The soil fine fraction content (clay + silt) is closely related to water retention at field capacity, the soil layer and site type, and without WRC to the temperature sum and site index and type, as well as the slope angle. The soil bulk density is related to organic matter, depth (layer) or alternatively to organic matter, slope and field estimated textural class (fine, medium, coarse). Water retention characteristics were found to be best determinable by the fine fraction content, depth and bulk density. Water content and air-filled porosity at field capacity are closely related to the fine fraction. This study provides novel models for further investigations that aim at improved prediction models for forest growth, hydrology and trafficability.

• Heiskanen, Natural Resources Institute Finland (Luke), Soil ecosystems, Neulaniementie 5, FI-70100 Kuopio, Finland E-mail: juha.heiskanen@luke.fi
• Hallikainen, Natural Resources Institute Finland (Luke), Applied statistical methods, Eteläranta 55, FI-96300 Rovaniemi, Finland E-mail: ville.hallikainen@luke.fi
• Uusitalo, Natural Resources Institute Finland (Luke), Forest technology and logistics, Korkeakoulunkatu 7, FI-33720 Tampere, Finland E-mail: jori.uusitalo@luke.fi
• Ilvesniemi, Natural Resources Institute Finland (Luke), Biorefinery and bioproducts, Tietotie 2, FI-02150 Espoo, Finland E-mail: hannu.ilvesniemi@luke.fi

The amount of water in peat soil is one factor affecting its bearing capacity, which is a crucial aspect in planning peatland timber harvesting operations. We studied the influence of weather variables on the variation of drained peatland growing season water conditions, here the ground water table depth (WTD). WTD was manually monitored four times in 2014 and three times in 2015 in 10–30 sample plots located in four drained peatland forests in south-western Finland. For each peatland, precipitation and evapotranspiration were calculated from the records of the nearest Finnish Meteorological Institute field stations covering periods from one day to four weeks preceding the WTD monitoring date. A mixed linear model was constructed to investigate the impact of the weather parameters on WTD. Precipitation of the previous four–week period was the most important explanatory variable. The four-week evapotranspiration amount was interacting with the Julian day showing a greater effect in late summer. Other variables influencing WTD were stand volume within the three-metre radius sample plot and distance from nearest ditch. Our results show the potential of weather parameters, specifically that of the previous four-week precipitation and evapotranspiration, for predicting drained peatland water table depth variation and subsequently, the possibility to develop a more general empirical model to assist planning of harvesting operations on drained peatlands.

• Hökkä, Natural Resources Institute Finland (Luke), Management and Production of Renewable Resources, Paavo Havaksen tie 3, FI-90014 Oulun yliopisto, Finland E-mail: hannu.hokka@luke.fi
• Uusitalo, Natural Resources Institute Finland (Luke), Green Technology, Kaironiementie 15, FI-39700 Parkano, Finland E-mail: jori.uusitalo@luke.fi
• Lindeman, Natural Resources Institute Finland (Luke), Green Technology, Kaironiementie 15, FI-39700 Parkano, Finland E-mail: harri.lindeman@luke.fi
• Ala-Ilomäki, Natural Resources Institute Finland (Luke), Green Technology, Jokiniemenkuja 1, FI-01370 Vantaa, Finland E-mail: jari.ala-ilomaki@luke.fi

Habitat loss and degradation are the main threats to biodiversity worldwide. For example, nearly 80% of peatlands in southern Finland have been drained. There is thus a need to safeguard the remaining pristine mires and to restore degraded ones. Ants play a pivotal role in many ecosystems and like many keystone plant species, shape ecosystem conditions for other biota. The effects of mire restoration and subsequent vegetation succession on ants, however, are poorly understood. We inventoried tree stands, vegetation, water-table level, and ants (with pitfall traps) in nine mires in southern Finland to explore differences in habitats, vegetation and ant assemblages among pristine, drained (30–40 years ago) and recently restored (1–3 years ago) pine mires. We expected that restoring the water-table level by ditch filling and reconstructing sparse tree stands by cuttings will recover mire vegetation and ants. We found predictable responses in habitat structure, floristic composition and ant assemblage structure both to drainage and restoration. However, for mire-specialist ants the results were variable and longer-term monitoring is needed to confirm the success of restoration since these social insects establish perennial colonies with long colony cycles. We conclude that restoring the water-table level and tree stand structure seem to recover the characteristic vegetation and ant assemblages in the short term. This recovery was likely enhanced because drained mires still had both acrotelm and catotelm, and connectedness was still reasonable for mire organisms to recolonize the restored mires either from local refugia or from populations of nearby mires.

• Punttila, Finnish Environment Institute, P.O. Box 140, FI-00251 Helsinki, Finland E-mail: pekka.punttila@ymparisto.fi
• Autio, Centre for Economic Development, Transport and the Environment in South Ostrobothnia, P.O. Box 252, FI-65101 Vaasa, Finland E-mail: olli.autio@ely-keskus.fi
• Kotiaho, University of Jyväskylä, Department of Biology & Environmental Sciences, P.O. Box 35, FI-40014 Jyväskylä, Finland E-mail: janne.kotiaho@jyu.fi
• Kotze, University of Helsinki, Department of Environmental Sciences, P.O. Box 65, FI-00014, University of Helsinki, Finland E-mail: johan.kotze@helsinki.fi
• Loukola, University of Oulu, Department of Biology, P.O. Box 3000, FI-90014 Oulu, Finland E-mail: olli.loukola@gmail.com
• Noreika, University of Helsinki, Department of Environmental Sciences, P.O. Box 65, FI-00014, University of Helsinki, Finland; University of Helsinki, Department of Biosciences, P.O. Box 65, FI-00014 University of Helsinki, Finland E-mail: norbertas.noreika@gmail.com
• Vuori, University of Jyväskylä, Department of Biology & Environmental Sciences, P.O. Box 35, FI-40014 Jyväskylä, Finland E-mail: anna@kureniemi.fi
• Vepsäläinen, University of Helsinki, Department of Biosciences, P.O. Box 65, FI-00014 University of Helsinki, Finland E-mail: kari.vepsalainen@helsinki.fi

• Wang, Key Laboratory for Silviculture and Conservation, Ministry of Education, Beijing Forestry University, 35 East Qinghua Road, Haidian District, Beijing 100083, China E-mail: wjx198979@163.com
• Li, Key Laboratory for Silviculture and Conservation, Ministry of Education, Beijing Forestry University, 35 East Qinghua Road, Haidian District, Beijing 100083, China E-mail: glli226@163.com
• Pinto, US Department of Agriculture, Forest Service, Rocky Mountain Research Station, 1221 South Main Street, Moscow, ID 83843, USA E-mail: jpinto@fs.fed.us
• Liu, Key Laboratory for Silviculture and Conservation, Ministry of Education, Beijing Forestry University, 35 East Qinghua Road, Haidian District, Beijing 100083, China E-mail: 1044902638@qq.com
• Shi, Key Laboratory for Silviculture and Conservation, Ministry of Education, Beijing Forestry University, 35 East Qinghua Road, Haidian District, Beijing 100083, China E-mail: shiwenhui2008@163.com
• Liu, Key Laboratory for Silviculture and Conservation, Ministry of Education, Beijing Forestry University, 35 East Qinghua Road, Haidian District, Beijing 100083, China E-mail: lyong@bjfu.edu.cn

• Heiskanen, Finnish Forest Research Institute, Suonenjoki Unit, Juntintie 154, FI-77600, Suonenjoki, Finland E-mail: juha.heiskanen@metla.fi
• Saksa, Finnish Forest Research Institute, Suonenjoki Unit, Juntintie 154, FI-77600, Suonenjoki, Finland E-mail: timo.saksa@metla.fi
• Luoranen, Finnish Forest Research Institute, Suonenjoki Unit, Juntintie 154, FI-77600, Suonenjoki, Finland E-mail: jaana.luoranen@metla.fi

• Hökkä, Finnish Forest Research Institute, Rovaniemi Research Unit, P.O. Box 16, FI-96301 Rovaniemi, Finland E-mail: hannu.hokka@metla.fi
• Hyttinen, Metsänhoitoyhdistys Keski-Suomi, Viitasaari, Finland E-mail: hh@nn.fi
• Marttila, University of Oulu, Water Resources and Environmental Engineering Lab, Oulu, Finland E-mail: hm@nn.fi
• Jämsen, Forestry Centre Keski-Suomi, Pihtipudas, Finland E-mail: jj@nn.fi
• Kløve, University of Oulu, Water Resources and Environmental Engineering Lab, Oulu, Finland E-mail: bk@nn.fi

• Ky-Dembele, Département Productions Forestières, Institut de l’Environnement et de Recherches Agricoles, 03 BP 7047 Ouagadougou 03, Burkina Faso & Swedish University of Agricultural Sciences, Southern Swedish Forest Research Centre, P.O. Box 101, SE-230 53 Alnarp, Sweden (catherine.dembele@slu.se) E-mail: kydembele@hotmail.com
• Bayala, World Agroforestry Centre, West Africa and Centre Regional Office, Sahel Node, BP E5118 Bamako, Mali E-mail: jb@nn.ml
• Savadogo, Département Productions Forestières, Institut de l’Environnement et de Recherches Agricoles, 03 BP 7047 Ouagadougou 03, Burkina Faso & Swedish University of Agricultural Sciences, Southern Swedish Forest Research Centre, P.O. Box 101, SE-230 53 Alnarp, Sweden E-mail: ps@nn.bf
• Tigabu, Swedish University of Agricultural Sciences, Southern Swedish Forest Research Centre, P.O. Box 101, SE-230 53, Alnarp, Sweden E-mail: mt@nn.se
• Odén, Swedish University of Agricultural Sciences, Southern Swedish Forest Research Centre, P.O. Box 101, SE-230 53, Alnarp, Sweden E-mail: pco@nn.se
• Boussim, Université de Ouagadougou, Unité de Formation et Recherche en Sciences de la Vie et de la Terre, 03 BP 7021, Ouagadougou 03, Burkina Faso E-mail: ijb@nn.bf

• Michopoulos, Forest Research Institute of Athens, Terma Alkmanos, Athens 115 28, Greece E-mail: mipa@fria.gr
• Baloutsos, Forest Research Institute of Athens, Terma Alkmanos, Athens 115 28, Greece E-mail: gb@nn.gr
• Economou, Forest Research Institute of Athens, Terma Alkmanos, Athens 115 28, Greece E-mail: ae@nn.gr

• Aphalo, University of Helsinki, Department of Biological and Environmental Sciences E-mail: pja@nn.fi
• Lahti, The Finnish Forest Research Institute E-mail: ml@nn.fi
• Lehto, University of Joensuu, Faculty of Forestry, Box 111, FI-80101 Joensuu, Finland E-mail: tarja.lehto@joensuu.fi
• Repo, The Finnish Forest Research Institute E-mail: tr@nn.fi
• Rummukainen, University of Joensuu, Faculty of Forestry, Box 111, FI-80101 Joensuu, Finland E-mail: ar@nn.fi
• Mannerkoski, University of Joensuu, Faculty of Forestry, Box 111, FI-80101 Joensuu, Finland E-mail: hm@nn.fi
• Finér, The Finnish Forest Research Institute E-mail: lf@nn.fi

• Nieminen, Finnish Forest Research Institute, Vantaa Research Centre, P.O. Box 18, FI-01301 Vantaa, Finland E-mail: mika.nieminen@metla.fi
• Ahti, Finnish Forest Research Institute, Vantaa Research Centre, P.O. Box 18, FI-01301 Vantaa, Finland E-mail: ea@nn.fi
• Nousiainen, Finnish Forest Research Institute, Vantaa Research Centre, P.O. Box 18, FI-01301 Vantaa, Finland E-mail: hn@nn.fi
• Joensuu, Forestry Development Centre Tapio, Soidinkuja 4, FI-00700 Helsinki, Finland E-mail: sj@nn.fi
• Vuollekoski, Finnish Forest Research Institute, Vantaa Research Centre, P.O. Box 18, FI-01301 Vantaa, Finland E-mail: mv@nn.fi

• Levula, University of Helsinki, Department of Forest Ecology, FIN-00014 University of Helsinki, Finland E-mail: janne.levula@helsinki.fi
• Ilvesniemi, University of Helsinki, Department of Forest Ecology, FIN-00014 University of Helsinki, Finland E-mail: hi@nn.fi
• Westman, University of Helsinki, Department of Forest Ecology, FIN-00014 University of Helsinki, Finland E-mail: cjw@nn.fi

Mechanical site preparation (MSP) is deliberate soil disturbance which is undertaken to improve the conditions for forest regeneration. Disc trenching and mounding are the dominant MSP practices currently used in Sweden and Finland. In this paper, the impacts of MSP on the soil, water quality, greenhouse gas (GHG) emissions and ground vegetation of mineral soil sites in Sweden and Finland are reviewed. The practices considered are patch scarification, mounding, inverting, disc trenching, and ploughing, which together represent a wide range of soil disturbance intensity. The environmental effects of MSP in this region have not been studied extensively. The environmental impact of MSP derives from the process of creating microsites which involves horizontal and/or vertical redistribution of soil and soil mixing. This typically affects decomposition, element circulation and leaching, vegetation coverage and uptake of nutrients and water, and possibly erosion and sediment exports. Following disc trenching or mounding the effects on GHG emissions appear to be minor over the first two years. For a few years after disc trenching concentrations in soil water collected below ridges are higher than that below furrows for some elements (e.g., NO₃^-, NH₄⁺, Mg²⁺, and total or dissolved organic C). The physical and chemical effects of ploughing remain detectable for several decades. There is little evidence about how the effects of forestry activities in upland areas on soil-water chemistry are transferred to adjacent surface water bodies, including what role streamside discharge areas play. MSP increases the tree biomass C store and may increase the total ecosystem C store. The impact of MSP on the cover and abundance of ground vegetation species depends on the composition of the original plant community, MSP intensity, and the establishment rate of different species. Species cover generally seems to decline for late succession understory species, while pioneer and ruderal species can benefit from the microsites created. Areas containing lichens which are used for reindeer forage require special consideration. More research is needed on the environmental effects of MSP, particularly regarding its long-term effects. Further efforts should be made to develop efficient site-preparation practices which better balance the disturbance intensity with what is needed for successful regeneration.

• Ring, Skogforsk (The Forestry Research Institute of Sweden), Uppsala Science Park, 751 83, Uppsala, Sweden https://orcid.org/0000-0002-8962-9811 E-mail: eva.ring@skogforsk.se
• Sikström, Skogforsk (The Forestry Research Institute of Sweden), Uppsala Science Park, 751 83, Uppsala, Sweden E-mail: ulf.sikstrom@skogforsk.se

At sites with either peat or mineral soils in large areas of boreal forests, high soil-water contents hamper tree growth and drainage can significantly increase growth. Hence, areas covering about 15 × 10⁶ ha of northern peatlands and wet mineral soils have been drained for forestry purposes. Usually ditches gradually deteriorate, thus reducing their functionality as drains, and ditch-network maintenance (DNM) might be needed to maintain stand growth rates enabled by the original ditching. This article reviews current knowledge on establishing the need for DNM in boreal forest stands, subsequent growth responses, and the financial outcome of the activity. The issues covered in the review are: (i) ditching, changes in ditches over time and the need for DNM; (ii) interactions between soil water and both stand properties and stand management; (iii) ground-water level (GWL) and tree growth responses to DNM; and (iv) financial viability of DNM. Conclusions about the current understanding of issues related to DNM are drawn and implications for DNM in practice are summarized. Finally, gaps in knowledge are identified and research needs are suggested.

• Sikström, The Forestry Research Institute of Sweden (Skogforsk), Uppsala Science Park, SE-751 83 Uppsala, Sweden E-mail: ulf.sikstrom@skogforsk.se
• Hökkä, Natural Resources Institute Finland (Luke), Management and Production of Renewable Resources, P.O. Box 16, FI-96301 Rovaniemi, Finland E-mail: hannu.hokka@luke.fi

• Cowan, Research School of Biological Sciences, Australian National University, Canberra, ACT 0200, Australia E-mail: iancowan@bigpond.com.au