Current issue: 58(5)
Articles containing the keyword 'ilmasto'
Category : Article
This review discusses whether forests are affected by biotic damages due to present or future environmental disturbances, and do environmental threats, such as air pollution and climatic change, weaken the condition of forest in a way that makes them vulnerable to damages by fungi and insect. The defence mechanisms of trees and factors affecting the development of an outbreak are described. Finally, the ways that air pollution and climatic change may affect biotic damages are discussed.
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Annila,
E-mail:
ea@mm.unknown
Methods involving the use of moving averages, trend surfaces and their combination are compared in deriving local values of monthly mean temperatures and precipitation sums from the observations made by the Finnish Meteorological Office. Correlation between meteorological variables and sea index, lake index and height above sea level were used in the trend surface method and in the combined method. Combined method, with a trend surface calculated from means of a long time period, was the most reliable method to estimate long local time series.
A method to calculate unbiased estimates of effective temperature sums from monthly mean temperatures is presented.
The PDF includes a summary in English.
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Ojansuu,
E-mail:
ro@mm.unknown
- Henttonen, E-mail: hh@mm.unknown
Climatological factors determining the natural northern boundary in Europe of oak (Quercus robur L.) were investigated. The natural northern boundary of oak corresponds in detail to the curve at which the growing season, beginning at +5°C in spring and ending at +10°C in autumn, is of a certain constant length. The northern boundaries for more oceanic plants can be explained by prolonged autumn activity. This is obviously the general explanation or the concept of oceanity. Oak spread markedly in Finland in the summers during 1961–1975, which on an average were as warm but much dried than those during 1931–1960. The importance of humidity for oak was discussed.
The PDF includes a summary in English.
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Solantie,
E-mail:
rs@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.
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Solantie,
E-mail:
rs@mm.unknown
An explorative study on wind conditions in a well-managed Scots pine (Pinus sylvestris L.) stand was made in Southern Finland. The wind velocity was recorded continually with two cup anomometers from April to August, 1964. The two levels used were 2 m and 9 m. The wind velocity was lower at 2 m than within the canopy at 9 m. The dependence on the absolute wind velocity at 9 metres was logarithmic. The wind velocity did affect the difference between daily minimum temperatures at the two levels; the difference in the maximum temperatures was affected only in May and August.
The PDF includes a summary in English.
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Leikola,
E-mail:
ml@mm.unknown
Category : Article
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.
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Mustonen,
E-mail:
sm@mm.unknown
The investigation is divided into statistical and experimental sections, the latter of which were conducted in a Vaccinium type Scots pine (Pinus sylvestris L.) stand with the aim of elucidating the interdependence of soil humidity and meteorological factors. The moisture content of pine needles and moss and wooden cylinders placed on the soil or slightly over the ground was determined by weighing. The results showed that there is correlation between the moisture content of the wooden cylinders and the relative humidity of air during the days without rain. Correlation between moisture content of pine needles and moss with the air was slightly poorer.
In the statistical section, based on meteorological observations made in the geophysical observatory at Sodankylä in Northern Finland in 1920-1943, and forest fire statistics of the area, forest fire days and days without forest fires were divided into 40 temperature-humidity groups. Of the 391 forest fires observed in the area, the cause of the fire was known in 353 cases, and 69% of these were caused by lightning. A forest fire danger index was calculated using the data. A sharp increase in the burned area when the index exceeded the limit k=0.3 seem to be explained by thunderstorms, which are the most notable cause of forest fires in the Sodankylä area.
The forest fire index was calculated also at four meteorological stations in different parts of the country using weather observations in 1927-1936. It appears that the number of days in which the k>0.1 decreases when proceeding northwards, obviously because of the shortening of the summer. On the other hand, the number of days in which k>0.3 increases towards the north.
The PDF includes a summary in English.
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Franssila,
E-mail:
mf@mm.unknown
The aim of the investigation was to estimate the effect of climate on the temperature observations and heating of buildings. Temperature data of observation stations in Finland and in the neighbouring countries near Finnish borders, in all 190 stations, was collected during heating season.
Heating season begins in the northern border of Finland in 20th of July, in Rovaniemi oin the Northern Finland in the middle of August, and 5th of September in the Southern coast of the country. Similarly, the heating season ends in 2.-10.6. in Southern and Central Finland, in June in Northern Finland, and in the middle of June in the Northernmost Finland, where heating season continued almost the whole year. In Southern Finland the length of heating season was 280 days. In the coldest heating season in 1942-1942 the heating decree-days increased most in the province of Varsinais-Suomi in Southern Finland. The increase decreased towards North. In the warmest heating season in 1929-1930 decrease of heating decree-days was similar in almost the whole country. The data can be used to define how different weather conditions affect the need of fuel.
The PDF includes a summary in German.
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Keränen,
E-mail:
jk@mm.unknown
The article discusses the thermal conditions in the northern limits of trees and some bushes in Finland. Temperature is the most important limiting factor for distribution of plant species. Precipitation variations, however, are small in Finland. The article lists the main features of thermal conditions during the different seasons in different parts of Finland. The northern limits and the thermal condition of the area are described for the following species: Scots pine (Pinus sylvestris L.) and Norway spruce (Picea abies (L.) H. Karst.), mezereon, buckthorn, common alder, linden, elm, maple, hazel, ash, oak, hybrid mountain ash, yew and Swedish whitebeam.
The PDF includes a summary in English.
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Keränen,
E-mail:
jk@mm.unknown
The growth of 35 exotic tree species in garden established in 1912 is discussed in the article. The site is located in Kulosaari, Helsinki in the Southern coast of Finland. The species represented the Chamaecyparis, Abies, Tsuga, Picea, Larix, Pinus, Betula, Fagus, Quercus, Juglans, Populus, Salix, Tilia, Acer, Prunus, Crataegus and Amelanchier families. All the tree species from northern continental climate and most of the species of temperate regions grew well or moderately well. Species form northern oceanic climate succeeded moderately well. The species from southern continental or oceanic climate did not endure the climate in Kulosaari. Definite conclusions were not possible to make, because the precise origin of the seedlings was not known, and there was usually only one tree from each species.
The PDF includes a summary in German.
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Tikka,
E-mail:
pt@mm.unknown
The article includes a dendrological review on the effect of climate to the success of cultivation of exotic tree species, based on literature and analysis of the existing Finnish field tests. The cultivation of an exotic tree species succeeds only if the seed has been procured from an area, which climate is similar to the place of cultivation. Climate is even more important than site quality.
Finnish climate is boreal and continental, and thus tree species of similar climate suit here best. In favorable site conditions it is possible to grow also species from boreal marine, and temperate climates. Finnish summers are not warm enough for species from temperate continental climate to get prepared for the winter, and the shoots can get frost damages. This may be compensated with a warm and sheltered site. If the species tolerates shading, it can be planted under sheltering trees. For species from maritime boreal climate, the Finnish summer tends to be too short, and the winters too cold. A suitable site is rich, warm and sheltered, and has preferably a protective sparse tree cover. Species from southern maritime climate cannot be grown in Finland. The provenance of the seeds is also very important. An important source of seeds are the successful plantations in Finland.
The PDF includes a summary in German.
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Ilvessalo,
E-mail:
li@mm.unknown
The investigations that have studied peat layers in peatlands have shown that the peatlands in several countries have layers containing tree stumps of different tree species. The stump layers have been explained by local hydrological changes that have caused paludification, or changes in climate.
Peat layers were studied in drained peatlands in Finland, and ditches were used to study the peat profiles. A peatland in Multia in Central Finland was studied in more detail. Tree stump layer patterns that would support the climate change explanation was not found in the Finnish peatlands. The peat changes usually gradually more oligotrophic towards the surface. The stump layers seemed to be caused by local drier periods. According to the layers of Sphagnum-peat near the bottom of the peatlands and the pollen studies indicate that the peatlands have been formed at different times. In South-West Finland, the peat profiles had more apparent layer patterns than in Central Finland, but these were not considered to be caused by changes in climate.
The PDF includes a summary in German.
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Lukkala,
E-mail:
ol@mm.unknown
