Current issue: 56(2)
Under compilation: 56(3)
Nearly every forest land in Finland has been burnt down by a wildfire at least once during the past 400–500 years. Slash and burn cultivation (1700–1920) was practised on 50–75 percent of Finland's forests, while prescribed burning (1920–1990) has been applied to 2–3 percent of the country's forests. Because of land-use changes and efficient fire prevention and control systems, the occurrence of wildfires in Finland has decreased considerably during the past few decades. Owing to the biodiversity and ecologically favourable influence of fire, the current tendency is to revive the use of controlled fire in forestry in Finland. Prescribed burning is used in forest regeneration and endeavours are being made to revert old conservation forests to the starting point of succession through forest fires.
The main features of the Finnish landscape are a result of preglacial erosion processes and the structural lines of the bedrock. The microstructure of the landscape was created by the Ice Age and its melting processes. Upon this base, human activities have created a palimpsest of cultural landscapes. The article describes the effects of slash-and-burn cultivation, tar production, cattle ranging and some other forest uses to the forest landscape.
The paper is based on a lecture given in the seminar ‘The forest as a Finnish cultural entity’, held in Helsinki in 1986. The PDF includes a summary in English.
Surface temperature during two prescribed burnings were measured in 1983 in Evo, Southern Finland. Surface temperatures in relation to the amount of slash burned, energy released during the fires, and the fire intensities were studied. The fire intensity was also measured during a third burn. The Lake Nimetön site was burned int the end of May. Due to the uneven distribution of slash, colonization by Calamagrostis arundinacea and the spring moisture, the burning was very uneven. Surface temperatures varied between 410–809°C and the intensity of fire was low (range 0–900 kW/m).
The fire intensity on the other sites burned in May was also low (880 kW/m). During the burn in August the surface temperatures varied between 701–869°C and the intensity of fire was moderate (1,170 kW/m). Slash was burned more evenly and more thoroughly due to the dryness of the site and slash and the fact that grasses and other herbs were not abundant.
The PDF includes a summary in Finnish.
Operating conditions affecting the quality of spot mounding by Bracke continuously advancing mounders were investigated on 66 regeneration areas (124 ha) in eastern Finland. The quality of mounds was classified as suitable (good or acceptable after additional compression) or unsuitable for planting. Models were constructed for the number of suitable planting spots obtained per hectare (good and acceptable mounds), the probability of successful mounding (≥1600 planting spots ha–1) and the probability of creating a suitable mound as a function of terrain, site and soil characteristics, as well as slash conditions (removed, fresh or dry logging residues). The average number of mounds created was 1892 ± 290 mounds ha–1, of which 1398 ± 325 mounds ha–1 (74%) were classified as suitable for planting. The quality of spot mounding was reduced by steep terrain, a thick humus layer and fresh logging residues. Stoniness and soil texture also affected the number of planting spots created. Mounding after logging residues had dried increased the number of planting spots by 191 spots ha–1 compared with mounding in the presence of fresh residues. Removing residues did not significantly increase the number of planting spots compared with mounding amongst dry residues. A thick humus layer, very stony soil, steep slopes and valley terrain decreased the number of planting spots by 150–450 spots ha–1. The number and quality of mounds varied considerably according to the operating conditions, but with careful selection of timing and sites the quality obtained by a continuously advancing mounder can be improved.
The article considers the relation of shifting cultivation to deforestation and degradation, and hence its impacts in terms of carbon emissions and sequestration potential. There is a need to understand these relationships better in the context of international policy on Reduced Emissions from Deforestation and Forest Degradation (REDD+). The article reviews the way in which shifting cultivation has been incorporated in global and national estimations of carbon emissions, and assembles the available information on shifting cultivation in Tropical Dry Forests (TDF) in Mexico, where it is widely practiced. It then takes the case of two villages, Tonaya and El Temazcal, which lie within the basin of the River Ayuquila in Jalisco, Mexico. Field data for the typical carbon stocks and fluxes associated with shifting cultivation are compared with stocks and fluxes associated with more intensive agricultural production in the same dry tropical forest area to highlight the carbon sequestration dynamics associated with the shortening and potential lengthening of the fallow cycles. The biomass density in the shifting cultivation system observed can reach levels similar to that of old growth forests, with old fallows (>20 years) having higher carbon stocks than old growth forests. Per Mg of maize produced, the biomass-related emissions from shifting cultivation in the traditional 12 year cycle are about three times those from permanent cultivation. We did not, however, take into account the additional emissions from inputs that result from the use of fertilizers and pesticides in the case of permanent agriculture. Shortening of the fallow cycle, which is occurring in the study area as a result of government subsidies, results in higher remaining stocks of carbon and lower emissions at the landscape level.