Current issue: 56(4)
Under compilation: 57(1)
Shoot losses due to maturation feeding by pine shoot beetles (Tomicus piniperda (L.) and T. minor (Hart.), Col., Scolytidae) and subsequent growth losses were studied in Scots pine (Pinus sylvestris L.) stands growing at different distances from a timber yard, where pine timber was stored during the years 1982–84. In autumn 1985, pine trees were felled at 20, 40, 80, 500 and 1,500 m distance from the timber yard, five trees in each distance class. Trees were analysed for beetle attack, needle biomass and growth. In autumn 1988, increment cores were taken from 20 trees in each distance class.
In 1985, different damage estimates showed that beetle damage was more than 10-fold in the crowns of pine trees growing close to the timber yard as compared to less damaged trees in greater distance. Crude needle biomass estimates indicated that the trees attacked most had lost more than half of the total foliage. Following three years of attack, basal area growth decreased for 2–3 years and recovered during the subsequent 3 years, the total period of loss thus being 5–6 years. The loss in volume growth during 1983–85 was ca. 70, 40, 20 and 10% at 20, 40, 80 and 500 m distance from the beetle source, respectively, compared to the stand at 1,500. Growth losses did not occur until the number of beetle-attacks, ”pegs”, exceeded ca. 200 per tree. The highest observed growth losses occurred in trees with more than 1,000 pegs per tree.
The PDF includes an abstract in Finnish
The writer reports in this discussion article of four stands in Finland that have died due to a bolt of lightning. A death of a group of trees because of lightning has been relatively uncommon for the forest professionals. The trees may not have no lightning marks. The four sites are presented in detail. Characteristic for this type of death of trees is, for instance, that trees have died within a circular area (of usually 30 m of diameter), only conifers have died, trees die from the top down, sometimes marks can be found in trees in the centre of the area, and under the bark may be brown patches or stripes.
An inventory of Scots pine (Pinus sylvestris L.) graft collection in Kolari (67°15’ N, 23°45’ S) showed that severe damage by arctic hare (Lepus timidus L.), root and bank vole (Microtus oeconomus Pallas and M. agrestis L.) and moose (Alces alces L.) was done to grafts in size and in rather poor condition. Furthermore, the damage by arctic hare was dependent on the dry matter content of the needles. Another inventory in a fertilization experiment in a pine pole-stage forest showed that nitrogen fertilization increased the damage by arctic hare. On the basis of the present results, an assumption was made that the formation of repellent substances against herbivorous mammals is connected with wintering process of northern pines.
The PDF includes a summary in Finnish.
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.
Increase in the elk (Alces alces L.) population and the problems of its grazing has called for detailed research. The present study concentrated on three observation areas representing northern, western and eastern parts of Finland. There were 28 field observers watching 68 elks.
Earlier investigations in Finland indicate that aspen (Populus tremula L.) is the staple diet of elk. This study reached different conclusions, probably largely because of aspen is gradually becoming an increasingly rare tree species in Finland. According to this study, the principal food of elk in the winter is willow (Salix sp.). In the whole country, willow accounts for about 70% of elk’s nutrition. In the Far North the percentage is approx. 90. Of the other tree species, the order of preference is: aspen, Scots pine, mountain ash, juniper and birch. In addition, in Western Finland where snow is less deep, lingonberry and blueberry shrubs are on the menu. Beard moss on the spruce was frequently eaten locally. Elk seems to have eaten mainly the last annual shoot of trees and bushes. In few cases it has gnawed the bark of Scots pine, aspen and willow. Elk consumes in average 340 twigs or terminal shoots per day in the winter. This corresponds to about 1.8 kg of food.
The problem of elks damaging Scots pine seedlings has been observed in Western Finland, were the elk population is higher. The article suggests that suitable feeding places would be left for elk in places that are unsuitable for agriculture or forestry. Leaving, for instance, birch seedlings in Scots pine stands has been noticed to attract elks and to increase the damage to pine.
The article includes an abstract in English and a summary in Swedish.
Observatons of drying of Norway spruce (Picea abies (L.) Karst.) stands increased in 1930s in Southern Finland. The aim of the study was to analyse the advance and causes of drying. The work was begun in 1930s before the Second World War, and the damages caused to the forests by the war was used as supplemental observations in the study. A special method, drying analysis, was developed to study the process. It was used both in cases of insect and fungal diseases in the four research areas in Raivola and Ruotsinkylä. In addition, 7 observation areas were studied.
Several causes for drying of the trees were observed in the Norway spruce stands. These included European spruce bark beetle (Dendroctonus micans), root rot (Heterobasidion annosum), pine weevils (Pissodes sp.), bark beetles and honey fungus (Armillaria mellea).
The role of primary and secondary causes for drying, resistance of the trees and the drying process are discussed. Finally, the influence of forest management in drying process is analysed. Forests in natural state can be considered to be in an ideal balance. On the other hand, forest management can be used to maintain the vitality and resistance of the forests. Drying of Norway spruce stands can be taken into consideration when the stands are managed.
The PDF includes a summary in German.
We describe the methodology applied in the 12th national forest inventory of Finland (NFI12) and describe the state of Finland’s forests as well as the development of some key parameters since 1920s. According to the NFI12, the area of forestry land (consisting of productive and poorly productive forest, unproductive land, and other forestry land) is 26.2 M ha. The area of forestry land has decreased from 1920s to 1960s due to expansion of agriculture and built-up land. 20% of the forestry land is not available for wood supply and 13% is only partly available for wood supply. The area of peatlands is 8.8 M ha, which is one third of the forestry land. 53% of the current area of peatlands is drained. The volume of growing stock, 2500 M m3, is 1.7 times the volume estimated in NFI1 in the 1920s for the current territory of Finland. The estimated annual volume increment is 107.8 M m3. The increment estimate has doubled since the estimate of NFI2 implemented in late 1930s. The annual mortality is estimated to 7 M m3, which is 0.5 M m3 more than according to the previous inventory. Serious or complete damage was observed on 2% of the productive forest available for wood supply. The amount of dead wood is on average 5.8 m3 ha–1 in productive forests. Since the NFI9 (1996–2003) the amount of dead wood has increased in South Finland and decreased in North Finland both in protected forests and forests available for wood supply (FAWS). The area of natural or almost natural forests on productive forest is 380 000 ha, out of this, 42 000 ha are in FAWS and 340 000 ha in protected forests.
We modelled the effect of habitat composition and roads on the number and occurrence of moose (Alces alces L.) damage in Ostrobothnia and Lapland using a zero-inflated count model. Models were developed for 1 km2, 25 km2 and 100 km2 landscapes consisting of equilateral rectangular grid cells. Count models predict the number of damage, i.e. the number of plantations and zero models the probability of a landscape being without damage for a given habitat composition. The number of moose damage in neighboring grid cells was a significant predictor in all models. The proportion of mature forest was the most frequent significant variable, and an increasing admixture of mature forests among plantations increased the number and occurrence of damage. The amount of all types of plantations was the second most common significant variable predicting increasing damage along with increasing amount of plantations. An increase in thinning forests as an admixture also increased damage in 1 km2 landscapes in both areas, whereas an increase in pine-dominated thinning forests in Lapland reduced the number of damage in 25 km2 landscapes. An increasing amount of inhabited areas in Ostrobothnia and the length of connecting roads in Lapland reduced the number of damage in 1 and 25 km2 landscapes. Differences in model variables between areas suggest that models of moose damage risk should be adjusted according to characteristics that are specific to the study area.
The literature on the most prominent forest damage related to even-aged and uneven-aged forest management regimes was reviewed. A questionnaire to expert researchers was conducted to estimate risks in even-aged and uneven-aged forest management chains in Finland. There are only a few empirical comparisons of damage risks in even- and uneven-aged stands in the literature. The results from the expert survey showed that the damage risks were higher in even-aged management in Norway spruce and Scots pine. However, the variation in the risks between individual chains and between individual causes was high. The highest risks in Scots pine were caused by moose (in even-aged chains) and harvesting damage (in uneven-aged chains). In Norway spruce, root rot caused the highest risks in both even-aged and uneven-aged chains. The higher risks in even-aged forestry are largely due to the many associated practices which favour various types of damage. However, there are some important exceptions: the damage risks may be higher in some uneven-aged stands, especially in Norway spruce stands infected with root rot where the utilization of undergrowth or natural regeneration can be risky. Moreover, the repeated thinnings in uneven-aged stands may lead to increased mechanical damage.
Ungulate browsing results in important damages on the forests, affecting their structure, composition and development. In the present paper, we examine the occurrence of browsing damage in Norwegian forests, using data provided by the National Forest Inventory along several consecutive measurements (entailing the period 1995–2014). A portfolio of variables describing the stand, site and silvicultural treatments are analyzed using classification trees to retrieve combinations related to browsing damage. Our results indicate that the most vulnerable forest stands are young with densities below 1400 trees ha–1 and dominated by birch, pine or mixed species. In addition, stand diversity and previous treatments (e.g. thinnings) increase the damage occurrence and other variables, like stand size, could play a role on forest susceptibility to browsing occurrence although the latter is based on weaker evidence. The methods and results of our study can be applied to implement management measures aiming at reducing the browsing damages of forests.
Forests are affected by climate change in various ways. This includes abiotic factors such as droughts, but also biotic damage by pest insects. There are numerous examples from cases where pest insects have benefitted from longer growing seasons or from warmer summers. Similarly, new pest insects have been able to expand their range due to climatic conditions that have changed from hostile to tolerable. Such seems to be the case with the nun moth (Lymantria monacha), an important defoliator of coniferous trees in Europe. For centuries, the species has had massive outbreaks across Central-Europe, while it has been a rare inhabitant in Northern Europe. Recently, the nun moth population in Finland has not only expanded in range, but also grown more abundant. This research note describes the results from the first years (2018–2019) of a monitoring program that is being conducted with pheromone traps across central and southern Finland. So far, the northernmost individuals were trapped near the 64 N degrees. However, there were more southern locations where no moths were trapped. The species was present in every trapping site below the latitude of 62 N degrees. More importantly, at some sites the abundance of the nun moth suggested that local forest damage may already occur. Given the current climatic scenarios for Fennoscandia, it is likely that the nun moth populations will continue to grow, which is why systematic surveys on their abundance and range expansions will be topical.