Articles containing the keyword 'snow'

Within the European Community snow damage affects an estimated 4 million m³ of timber every year, causing significant economic losses to forest owners. In Northern Europe, for example, the occurrence of snow damage has increased over the last few decades mainly due to the increase in total growing stock. The most common form of damage is stem breakage, but trees can also be bent or uprooted. Trees suffering snow damage are also more prone to consequential damage through insect or fungal attacks.

Snow accumulation on trees is strongly dependent upon weather and climatological conditions. Temperature influences the moisture content of snow and therefore the degree to which it can accumulate on branches. Wind can cause snow to be shed, but can also lead to large accumulations of wet snow, rime or freezing rain. Wet snow is most likely in late autumn or early spring. Geographic location and topography influence the occurrence of damaging forms of snow, and coastal locations and moderate to high elevations experience large accumulations. Slope plays a less important role and the evidence on the role of aspect is contradictory. The occurrence of damaging events can vary from every winter to once every 10 years or so depending upon regional climatology. In the future, assuming global warming in northern latitudes, the risk of snow damage could increase, because the relative occurrence of snowfall near temperatures of zero could increase.

The severity of snow damage is related to tree characteristics. Stem taper and crown characteristics are the most important factors controlling the stability of trees. Slightly tapering stems, asymmetric crowns, and rigid horizontal branching are all associated with high risk. However, the evidence on species differences is less clear due to the interaction with location. Management of forests can alter risk through choice of regeneration, tending, thinning and rotation. However, quantification and comparison of the absolute effect of these measures is not yet possible. An integrated risk model is required to allow the various locational and silvicultural factors to be assessed. Plans are presented to construct such a model, and gaps in knowledge are highlighted.

• Nykänen, E-mail: mn@mm.unknown
• Broadgate, E-mail: mb@mm.unknown
• Kellomäki, E-mail: sk@mm.unknown
• Peltola, E-mail: hp@mm.unknown
• Quine, E-mail: cq@mm.unknown

The purpose of this article was to collate the literature on fungal diseases that occur on seedlings in forest nurseries. It describes the symptoms of the diseases, the infection pattern of each fungus and the possibilities of controlling the diseases. As background a short introduction is given on forests and nursery practices in Finland.

• Lilja, E-mail: al@mm.unknown
• Kurkela, E-mail: tk@mm.unknown
• Lilja, E-mail: sl@mm.unknown
• Rikala., E-mail: rr@mm.unknown

Snow damage to forests in Southern Finland in November 1991 was examined in relation to meteorological conditions. The combined effect of different factors proved to be necessary for severe damage. First, the snow load, in terms of precipitation, should exceed a certain limit. The limit can be set for weak or moderate damage at about 40 mm and for very severe damage at about 60 mm. Second, temperature at the time of precipitation should be above 0°C, which enables the slightly wet snow to attach to twigs during the subsequent period with temperature below 0°C. On the other hand, temperatures exceeding 0.6°C prohibit damage by permitting the snow load to fall from the branches. Wind speed exceeding 9 ms^-1, as observed 15 m above ground, were strong enough to dislodge the snow which is not attached, and thus reduce the damage. There are few statistics either of snow damage or of the relation between the snow damage and precipitation. However, there is causal connection between snow damage and heavy snowfalls. Therefore, the regions with a high frequency of heavy snowfalls, as indicated by orographical features and occurrence of thick snow cover, were investigated.

• Solantie, E-mail: rs@mm.unknown

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

• Solantie, E-mail: rs@mm.unknown

Snow and rime, attached to branches of conifers, seriously damaged forests in a region of 11,000 km² in Southern Finland during a passage of two nearly occluded cyclones in 1959. The roles of different weather elements were studied by considering the variations occurring in them over this region and its surroundings. Damage occurred only inside an accentuated pattern of copious orographic precipitation. Precipitation only became attached to and retained on branches in such parts of the area where temperature varied on both sides of freezing point but did not exceed 0.6°C. Furthermore, damage only occurred in forests where rime formed (above a certain level and on sloping towards the prevailing wind).

The PDF includes a summary in English.

• Solantie, E-mail: rs@mm.unknown
• Ahti, E-mail: ka@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

The mobility of logging tractors was tested in the winter 1969 on difficult snow conditions to gather information for planning of logging operations and for logging machinery design. The tractors tested were Clark Ranger 666, Timberjack C, Valmet Terra, Ford Brunett 5000, Fiskars 510, BM-Volvo SM 660, BM Volvo SM 661, Ford Country 6, MF-Robur I and BM-Boxer T-350.

According to the results, there is a preference of tracked vehicles in difficult snow conditions compared to wheeled tractors. Ford Country with long and bearing full-tracks proved to have the best mobility. On downhill grades it was found significant differences between three-quarter-track-tractors and skidders, although the performance on level ground and uphill grades was relatively similar. The tracked vehicles can easier move on the packed snow layer and reach a higher speed.

The driving speed does not increase significantly until the density of snow has entirely changed through getting wet. Wet top layer of snow affects positively on driving, because it increases packing of the snow. Increasing density of the snow improves especially the mobility of broad-tired wheeled tractors. To be able to predict the driving speed of a tractor in winter working conditions one must know the depth of the snow layer and the density of the snow and the grade of the slope. In addition, the passages on the same route and the packing of the snow must be regarded.

The PDF includes a summary in English.

• Silvennoinen, E-mail: us@mm.unknown
• Haarlaa, E-mail: rh@mm.unknown

Exceptionally widespread snow damages occurred in January 1959 in the southern coastal region of Finland. An inquiry showed that significant devastation had occurred over an area of 42,620 ha. The purpose of the present investigation was to study the susceptibility to snow damages of different stands in different locations. Only the stem breakage was recorded. 924 stands along 92 one-kilometre lines were studied in the western continuation of Salpausselkä ridge in the summer 1960. A supplementary study was carried out in 1961 in separate stands.

Most heavily damaged stands were found in a damage zone closest (31–40 km) to the coast of Gulf of Finland. The damages were 39% fewer in the zone 61–70 km from the coast. No stands over 140 m above sea level escaped damage. Stands on the edge of an open area such as a field, lake etc. fared better than areas within the forest. Eastern slopes were more susceptible for snow damages in these weather conditions. Also, conifers were more frequently damaged than deciduous trees. Dense stands, and stands aged 61–100 years had most damages.

The PDF includes a summary in English.

• Suominen, E-mail: os@mm.unknown

Finnish tree species have adapted differently to heavy snow loads that occur especially in fell areas in Kuusamo and Salla as well as Maanselkä area in Sotkamo and Rautavaara in Northern Finland. Norway spruce (Picea abies Karst. L) is adapted better than Scots pine (Pinus sylvestris L.). The aim of this study was to investigate how crown and stem form of Norway spruce in the snow damage area of Maanselkä area differ from other areas in the same region.  

Relatively broad crown at the base of the stem, quickly tapering crown and narrow and even upper crown were typical for trees growing in the snow damaged areas. The higher the altitude is, the stronger tapering the crown is. The tapering begins usually in a height of 4-5 meters. Even the stem diameter begins to taper strongly at this height. In the areas where heavy snow does not cause snow damage, top of crown is broader. Also, in the snow damage areas the damaged trees seem to have broader crown shape than the trees with little damages.  

Height of the trees decreases in the snow damage areas compared to forests in lower altitudes, which can be caused both by wind and snow load. 

The article includes a German summary. 

• Mikola, E-mail: pm@mm.unknown

Broadcast sowing on snow was relatively new method in the beginning of the 20^th century in Finland, and the experiences of regeneration were diverse. The aim of the survey was to study the success rate of regeneration in the oldest and largest areas regenerated with this sowing method in Tuomarniemi district. Scots pine (Pinus sylvestris L.) was the most common tree species, but also Norway spruce (Picea abies (L.) H. Karst.) and European larch (Larix decidua Mill.) were used in broadcast sowing on snow.

According to the study, the success of broadcast sowing on snow was as good as patch sowing and sowing in furrows in the sites typical for Tuomarniemi. The regeneration areas were often drained peatlands or paludified lands. When sowing is done using Norway spruce seeds, site preparation either by broadcast burning or scalping with hoe is recommended. Mixed sowing with pine and spruce seldom succeeded due to the differences in site requirements of the species and growth of seedlings. Sowing of Scots pine succeeded well on the drained peatlands. Sowing should be done some years after draining to let the peat dry and sink. Site preparation is needed in sites growing Polytrichum-moss. Broadcast burned areas larger than 10 hectares seemed to regenerate poorer than sites in average, possibly due to dryness of the sites. Trials with European larch were successful, and the growth of the seedlings acceptable despite the sites being relatively poor for the species.

The PDF includes a summary in German.

• Borg, E-mail: lb@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

Snow cover and ground frost was studied in 29 forest stands in Southern and Central Finland in 1957–1959. The tree species influenced greatly accumulation of snow on the forest floor. Norway spruce (Picea abies (L.) Karst.) retains snow in its crown. In addition, snow and water falling from the branches compress the snow cover under the trees, and the ground freezes deeper because of the shallow snow cover. In the spring, the dense crown prevents rain and radiation reaching the ground, which remains cold longer. However, ground frost may protect spruce, which has a weak root system, from wind damages.

Scots pine (Pinus sylvestris L.) has similar, but milder, effects on snow cover within the forest. The crowns of pine seedlings and young trees pass snow easily, but later the crowns intercept it considerably. The lower branches are, however, high up and the snow is evenly spread on the ground. The deciduous trees intercept little snow and in the spring the snow smelts and the frozen soil thaws early. The snow conditions of deciduous forests are, however, changed by a spruce undergrowth.

It can be assumed that the unfavourable conditions in spruce forests can be alleviated by thinning. Also, mixture of pine and deciduous trees can transform the conditions more favourable in the spruce stands.

The PDF includes a summary in English.

• Yli-Vakkuri, E-mail: py@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

Two experiments were conducted in Punkaharju and Leivonmäki in the Central Finland in 1966-67 where the spread of the snow blight caused by Phacidium infestans Karst. was investigated in rows of excised branches from a ten-year-old stand of Scots pine (Pinus sylvestris L.). Ericaceous plants (Calluna vulgaris (L.) Hull and Vaccinium vitis-idaea L.) infected with snow moulds were used to determine their influence on the spread of snow blight.

The results show that significant inhibition of snow blight in Scots pine can be achieved with foliage of ericaceous evergreens. The mechanism of this inhibition is an object of conjecture. In healthy ericaceous vegetation it might be caused by saprophytic fungi living on surface of plants or by some constituent of the foliage. In the case of dead ericaceous foliage, the cause of inhibition seems to be the antagonism of other snow moulds. The antagonism of certain saprophytic organism is well known.

The observed inhibition suggests that ericaceous vegetation may be helpful for reforestation by offering a natural control of snow blight, when seedlings of Scots pine do not stand above the surrounding vegetation.

The PDF includes a summary in Finnish.

• Kurkela, E-mail: tk@mm.unknown

• Lehtonen, Finnish Meteorological Institute, P.O. Box 503, FI-00101 Helsinki, Finland E-mail: ilari.lehtonen@fmi.fi
• Hoppula, Finnish Meteorological Institute, P.O. Box 503, FI-00101 Helsinki, Finland E-mail: petri.hoppula@fmi.fi
• Pirinen, Finnish Meteorological Institute, P.O. Box 503, FI-00101 Helsinki, Finland E-mail: pentti.pirinen@fmi.fi
• Gregow, Finnish Meteorological Institute, P.O. Box 503, FI-00101 Helsinki, Finland E-mail: hilppa.gregow@fmi.fi

• Zubizarreta-Gerendiain, Technical University of Lisbon, School of Agriculture, Forest Research Centre, Lisbon, Portugal E-mail: azg@nn.po
• Pellikka, University of Helsinki, Dept. of Geosciences and Geography, Helsinki, Finland E-mail: pp@nn.fi
• Garcia-Gonzalo, Technical University of Lisbon, School of Agriculture, Forest Research Centre, Lisbon, Portugal E-mail: jgg@nn.po
• Ikonen, University of Eastern Finland, School of Forest Sciences, Joensuu, Finland E-mail: vpi@nn.fi
• Peltola, University of Eastern Finland, School of Forest Sciences, Joensuu, Finland E-mail: heli.peltola@uef.fi

• Gregow, Finnish Meteorological Institute, Helsinki, Finland E-mail: hilppa.gregow@fmi.fi
• Peltola, University of Eastern Finland, Faculty of Forest Sciences, Joensuu, Finland E-mail: heli.peltola@uef.fi
• Laapas, Finnish Meteorological Institute, Helsinki, Finland E-mail: ml@nn.fi
• Saku, Finnish Meteorological Institute, Helsinki, Finland E-mail: ss@nn.fi
• Venäläinen, Finnish Meteorological Institute, Helsinki, Finland E-mail: av@nn.fi

• Martín-Alcón, Forest Technology Center of Catalonia, Solsona, Lleida, Spain E-mail: santiago.martin@ctfc.es
• González-Olabarría, Forest Technology Center of Catalonia, Solsona, Lleida, Spain E-mail: jrgo@nn.es
• Coll, Forest Technology Center of Catalonia, Solsona, Lleida, Spain E-mail: lc@nn.es

• Kellomäki, University of Eastern Finland, School of Forest Sciences, Joensuu, Finland E-mail: seppo.kellomaki@uef.fi
• Maajärvi, University of Eastern Finland, School of Forest Sciences, Joensuu, Finland E-mail: mm@nn.fi
• Strandman, University of Eastern Finland, School of Forest Sciences, Joensuu, Finland E-mail: hs@nn.fi
• Kilpeläinen, University of Eastern Finland, School of Forest Sciences, Joensuu, Finland E-mail: ak@nn.fi
• Peltola, University of Eastern Finland, School of Forest Sciences, Joensuu, Finland E-mail: hp@nn.fi

• Gregow, Finnish Meteorological Institute, P.O. Box 503, FI-00101 Helsinki, Finland E-mail: hilppa.gregow@fmi.fi
• Puranen, Finnish Meteorological Institute, P.O. Box 503, FI-00101 Helsinki, Finland E-mail: up@nn.fi
• Venäläinen, Finnish Meteorological Institute, P.O. Box 503, FI-00101 Helsinki, Finland E-mail: av@nn.fi
• Peltola, University of Joensuu, Faculty of Forest Sciences, P.O. Box 111, FI-80101 Joensuu, Finland E-mail: heli.peltola@uef.fi
• Kellomäki, University of Joensuu, Faculty of Forest Sciences, P.O. Box 111, FI-80101 Joensuu, Finland E-mail: seppo.kellomaki@uef.fi
• Schultz, Finnish Meteorological Institute, P.O. Box 503, FI-00101 Helsinki, Finland E-mail: ds@nn.fi

• Vajda, Finnish Meteorogical Institute, Climate and Global Change, P.O. Box 503, FI-00101 Helsinki, Finland E-mail: andrea.vajda@fmi.fi
• Venäläinen, Finnish Meteorogical Institute, Climate and Global Change, P.O. Box 503, FI-00101 Helsinki, Finland E-mail: av@nn.fi
• Hänninen, Geological Survey of Finland, P.O. Box 96, FI-02151 Espoo, Finland E-mail: ph@nn.fi
• Sutinen, Geological Survey of Finland, P.O. Box 77, FI-96101 Rovaniemi, Finland E-mail: rs@nn.fi

• Zhu, Institute of Applied Ecology, Chinese Academy of Sciences, Wenhua Road 72, Shenyang 110016, China E-mail: zrms29@yahoo.com
• Li, Institute of Applied Ecology, Chinese Academy of Sciences, Wenhua Road 72, Shenyang 110016, China; Graduate School of Chinese Academy of Sciences, Yuquan Road 19-A, Beijing, 100039, China E-mail: xfl@nn.cn
• Liu, Institute of Applied Ecology, Chinese Academy of Sciences, Wenhua Road 72, Shenyang 110016, China; Graduate School of Chinese Academy of Sciences, Yuquan Road 19-A, Beijing, 100039, China E-mail: zgl@nn.cn
• Cao, Institute of Applied Ecology, Chinese Academy of Sciences, Wenhua Road 72, Shenyang 110016, China E-mail: wc@nn.cn
• Gonda, Faculty of Agriculture, Niigata University, Ikarashi 2-8050, Niigata, 950-2181, Japan E-mail: yg@nn.jp
• Matsuzaki, Faculty of Agriculture, Niigata University, Ikarashi 2-8050, Niigata, 950-2181, Japan E-mail: tm@nn.jp

• Lilja, Finnish Forest Research Institute, Vantaa, Finland E-mail: arja.lilja@metla.fi
• Poteri, Finnish Forest Research Institute, Suonenjoki, Finland E-mail: mp@nn.fi
• Petäistö, Finnish Forest Research Institute, Suonenjoki, Finland E-mail: rlp@nn.fi
• Rikala, Finnish Forest Research Institute, Suonenjoki, Finland E-mail: rr@nn.fi
• Kurkela, Finnish Forest Research Institute, Vantaa, Finland E-mail: tk@nn.fi
• Kasanen, University of Helsinki, Department of Forest Sciences, Helsinki, Finland E-mail: rk@nn.fi