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Parkano, Finland

The Finnish Forest Research Institute , known as Metla, is a subordinate agency to the Ministry of Agriculture and Forestry of the Government of Finland. It has statutory duties to promote, through research, the economical, ecological, and socially sustainable management and use of forests. Metla is one of Europe's largest forestry research institutes, with an annual budget of around €40 million and 9 main research units. Wikipedia.

The objective of the study was to ascertain the relationship of thinning intensity of downy birch (Betula pubescens Ehrh.) stands with height, crown, and diameter development as well as pulpwood, stem volume, and biomass increment using long-term (20-30 years) field experiments. Diameter growth of birches increased with thinning intensity during the first 15 years from thinning in all development phases, though after that it did so only for the youngest stands. The thinning response was low. Thinning intensity had no influence on increase in height. In terms of stem volume with bark, the mortality in unthinned stands during the study period was 30-45 m3 ha-1. The mean stem number in unthinned birch thickets fell from 25 000 ha-1 at a dominant height of 7 m to 3000 ha-1 at 18 m. The stem volume increment over the first 15 years was highest (5-6 m3 ha-1 a-1) on the very lightly thinned or unthinned plots, but later there was no significant difference between initial thinning intensities. The maximum above-ground leafless biomass (over 100 Mg ha-1) was achieved on very lightly thinned plots. Also, the total production (including thinning removal) of biomass or stem volume or even the production of pulpwood increased with stand density, with these values being greatest for very lightly thinned or unthinned plots. During 50-year rotation, the highest leafless above-ground biomass production was 2.5 Mg ha-1 a-1 as a mean value from the experiments. The highest mean annual production of pulpwood (d > 6.5 cm) was 3.2 m3 ha-1a-1, and, in practice, no saw timber or veneer timber was produced, because of the small size and low quality of the stems. A thinning in downy birch stands increased slightly the size of stems to be removed in future cuttings, but with exception for very light thinning it decreased the production of biomass and merchantable wood. Source

Wallenius T.,Finnish Forest Research Institute
Silva Fennica | Year: 2011

Steep decline in forest fires about a century ago occurred in coniferous forests over large areas in North America and Fennoscandia. This poorly understood phenomenon has been explained by different factors in different regions. The objective of this study is to evaluate the validity of the four most commonly suggested causes of the decrease in forest fires: fire fighting, over-grazing, climate change and human influence. I compiled the available dendrochronological data and estimated the annually burned proportions of Pinus-dominated forests in four subcontinental regions during the past 500 years. These data were compared to the development of fire suppression, grazing pressure, climate and human livelihoods. The annually burned proportions declined over 90% in all studied regions. In three out of the four regions fires decreased decades before fire suppression began. Available drought data are annually well correlated with fires but could not explain the decrease of the level in annually burned areas. A rapid increase in the number of livestock occurred at the same time with the decrease in fires in the Western US but not in Fennoscandia. Hence, fire suppression in Central Fennoscandia and over-grazing in the Western US may have locally contributed to the reduction of burned areas. More general explanation is offered by human influence hypothesis: the majority of the past forest fires were probably caused by humans and the decrease in the annually burned areas was because of a decrease in human caused fires. This is in accordance with the old written records and forest fire statistics. The decrease in annually burned areas, both in Fennoscandia and the United States coincides with an economic and cultural transition from traditional livelihoods that are associated with high fire use to modern agriculture and forestry. Source

Larjavaara M.,Finnish Forest Research Institute | Muller-Landau H.C.,Smithsonian Tropical Research Institute
Methods in Ecology and Evolution | Year: 2013

Tree height is a key variable for estimating tree biomass and investigating tree life history, but it is difficult to measure in forests with tall, dense canopies and wide crowns. The traditional method, which we refer to as the 'tangent method', involves measuring horizontal distance to the tree and angles from horizontal to the top and base of the tree, while standing at a distance of perhaps one tree height or greater. Laser rangefinders enable an alternative method, which we refer to as the 'sine method'; it involves measuring the distances to the top and base of the tree, and the angles from horizontal to these, and can be carried out from under the tree or from some distance away. We quantified systematic and random errors of these two methods as applied by five technicians to a size-stratified sample of 74 trees between 5.7 and 39.2 m tall in a Neotropical moist forest in Panama. We measured actual heights using towers adjacent to these trees. The tangent method produced unbiased height estimates, but random error was high, and in 6 of the 370 measurements, heights were overestimated by more than 100%. The sine method was faster to learn, displayed less variation in heights among technicians, and had lower random error, but resulted in systematic underestimation by 20% on average. We recommend the sine method for most applications in tropical forests. However, its underestimation, which is likely to vary with forest and instrument type, must be corrected if actual heights are needed. © 2013 British Ecological Society. Source

Saksa T.,Finnish Forest Research Institute
Forest Ecology and Management | Year: 2013

In southern Finland, large-scale stump harvesting from regeneration areas began in the early 2000s. At that time, stump harvesting and additional soil scarification for planting was performed simultaneously. The aim of this study was to investigate the regeneration result, particularly the outcome of the natural regeneration of birch after stump harvesting, compared to the result achieved on a conventionally soil prepared area without stump lifting. The study material consisted of 37 stump-harvested areas 4-9. years old, and 10 conventionally soil prepared regeneration areas of a corresponding age. In the case of Norway spruce planting, the result did not differ between stump-harvested and conventionally soil prepared areas, but the share of pure coniferous stands after pre-commercial thinning was estimated to be 30% after stump harvesting and 50% in conventional regeneration areas. In stump-harvested areas, the share of disturbed soil surface seemed remarkably higher and the time for seedling emergence longer than in conventionally soil prepared areas without stump lifting. The number of Scots pine seedlings was somewhat higher after stump harvesting than after conventional soil preparation, but there was great variation between regeneration areas. As for Norway spruce, there were fewer natural seedlings on stump-harvested areas. The number of birch seedlings was somewhat higher after stump lifting, but there was huge variation between regeneration areas. Most birch-rich regeneration areas were discovered after the stump harvest; the maximum mean density was over 60,000 birch seedlings ha-1. Birch regeneration was most abundant on fine textured, moist mineral soils or peat layered spots. The mean temperature in May and June during the first summer, and rainfall in May and June during the second summer after the stump harvest, correlated positively with the abundance of birch seedlings. © 2012 Elsevier B.V. Source

Wall A.,Finnish Forest Research Institute
Forest Ecology and Management | Year: 2012

The increased removal of biomass from the forest sites with whole-tree harvesting has raised concern over the sustainability of site productivity. In this study, the results from eighty-six studies that quantify the short-term effects of whole-tree harvesting as compared with stem-only harvesting on soil- and tree-based indicators of site productivity were reviewed with the aim of estimating the risks of both negative and positive impacts on site productivity. The risk was defined as the combination of the probability of occurrence of an impact in an indicator of site productivity and the magnitude of the impact. According to risk analysis of this study, soil pH, P, K, Ca, Mg and tree diameter were priority indicators of site productivity on which to act to mitigate risks of site productivity decline following whole-tree harvesting. Following clear-cutting, the probability of occurrence of a negative effect of whole-tree harvesting on these indicators of site productivity was 31-39% and the mean decrease 13-60%. The results showed that the risk level of change in indicators of site productivity following clear-cutting with whole-tree harvesting might be high enough to justify a need for mitigation measures. Following thinning with whole-tree harvesting, the probability of occurrence of the negative effects and the risk levels were lower in comparison to clear-cutting. Therefore, mitigation measures at thinning may not be needed. © 2012 Elsevier B.V. Source

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