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The prescribed burning of a 7.3 ha clear-cut and a 1.7 ha partially cut forest (volume 150 m3/ha) was carried out in Evo (61°12'N, 25°07'E) on 1 June 1992. The forest was a mesic Myrtillus site type forest dominated by Norway spruce (Picea abies (L.) Karst.). Practically all the trees and the above-ground parts of the understorey vegetation died in the fire, while the mor layer was thinned by an average of 1.5 cm. A study was made on the change of germinated seedling populations in time and their dependence on environmental factors. Seedlings of Norway spruce, Scots pine (Pinus sylvestris L.), silver birch (Betula pendula Roth), pubescent birch (B. pubescens Ehrh.) and rowan (Sorbus aucuparia L.) were inventoried in 1993 and in 1994 on permanent plots, four times per growing season. Autoregression models were used to compare regeneration of tree species in the burned forest with regeneration in the burnt clear-cut area, and to study the effect of distance from nearest seed source to regeneration. The average number of seedlings germinating in 1993 was higher than in 1994, probably because of differences between these consecutive years in regard to the amount of seed rain and weather conditions. The number of Norway spruce and rowan seedlings was higher inside the forest area than in the clear-cut area. The distance to the bordering forest and to the closest seed trees did not explain the result. It is suggested that the more stable microclimatic conditions under the shade of dead trees promote germination and seedling establishment in the forest area. As rowan is a bird-dispersed species, it is likely that dead trees help the dispersal of rowan seeds by providing birds places to sit and defecate. The shade provided by dead trees may influence the further succession of the tree stand and vegetation composition and diversity.

The prefire fungal flora (polypores and corticoid fungi) of 284 dead trees, mainly fallen trunks of Norway spruce (Picea abies), was studied in 1991 in an old, spruce-dominated mesic forest in southern Finland. Species diversity of the prefire fungal flora was very high, including a high proportion of locally rare species and four threatened polypore species in Finland. In 1992 part of the study area (7.3 ha) was clear-cut and a 1.7 ha forest stand in the center of study area was left standing with a tree volume of 150 m3/ha, and later on (June 1st) in the same year the whole area was burned. Burning was very efficient and all trees in the forest stand were dead one year after the fire. Also the ground layer burned almost completely. In 1993 the fungal flora of the 284 sample trees was studied again. Most of the trees had burned strongly and the fungal species diversity and the evenness in community structure had decreased considerably as compared with the prefire community. Species turnover was also great, especially in corticoid fungi. Greatest losses in the species numbers occurred in moderately and strongly decayed trees, in coniferous trees and in very strongly burned trees. Fungal flora of non-decayed and slightly decayed trees, deciduous trees and slightly burned trees seemed to have survived the fire quite well, and in these groups the species numbers had increased slightly as compared with the prefire community. Fungal species suffering from fire (anthracophobe species) were mainly growing in moderately and strongly decayed trees before the fire, whereas species favoured by fire (anthracophile species) were growing in less decayed trees. No fruitbodies of threatened polypores or other ‘old-forest species’ of polypores were found again after fire. Some very common and effective wood-rotting fungi (e.g. Fomitopsis pinicola, Fomes fomentarius, Antrodia serialis) survived the fire quite well (anthracoxene species). Species favoured by fire were mainly ruderal species which can utilize new, competition-free resources created by fire, and species that have their optima in dry and open places also outside forest-fire areas. Some rarities, e.g. Phanerochaete raduloides and Physisporinus rivulosus, were favoured by fire.

The colonisation of a burned clear-cut by ants in southern Finland was monitored using pitfall traps, artificial nest sites, and direct nest sampling from the ground and stumps. Clearcutting and fire seemed to have destroyed wood-ant colonies ( group), and also other mature-forest species suffered from fire. Nylander was able to survive only in less severely burned moist sites, whereas it benefitted from the enhanced light conditions in a non-burned clear-cut. The fire resulted in an essentially ant-free terrain into which pioneering species immigrated. The mortality of nest-founding queens appeared to be high. The results supported the hypothesis that the pioneering species tend to be those that are capable of independent colony founding, followed by species founding nests through temporary nest parasitism. The succession of the burned clear-cut differed from that of the non-burned one, suggesting that habitat selection in immigration and priority effects, i.e. competition, introduce deterministic components in the successional pathways of boreal ant communities. Formica rufaMyrmica ruginodis

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 and the spring moisture, the burning was very uneven. Surface temperatures varied between 410â809°C and the intensity of fire was low (range 0â900 kW/m).Calamagrostis arundinacea

This study deals with the succession of vegetation and tree stand in 16 mesic site type Scots pine ( L.) plantations after prescribed burning in Evo, Southern Finland. The oldest tree stands studied were about 30-year-old. The growth of trees followed the height index of type. The vegetation was first mesic, dominated by grasses and herbs, turning more xeric after four years. This change was accelerated by treatment with herbicides. After the closure of tree stand, vegetation became more characteristic of forest vegetation, but pioneer species and composition disappeared slowly. The basic characters of vegetation succession could be clearly described by DCA ordination and TWINSPAN classification. The study confirmed that type has succession phases which are typical for each age phases as Cajanderâs forest site type theory has proposed. However, differences in primary and secondary site factors have their own effects on the vegetation of the succession phases.MyrtillusPinus sylvestrisMyrtillusMyrtillus