Naturvårdsbränningens effekter på botten- och fältskiktsvegetation

Forest fires are an important part of the boreal forest ecosystem but have become very reduced in Sweden over the past 100 years. To recreate this feature in nature, prescribed forest fire has become a management method used to promote biodiversity. The purpose of this study was to investigate the effects of prescribed forest fire on the ground and field layer vegetation in terms of vegetation structure, species composition, coverage ratio, biomass and soil pH. The study was conducted in the Brännan Nature Reserve where prescribed forest fires have been implemented on several occasions during the past 21 years, which also made it possible to compare several areas and investigate effects over time. Four sub-areas were studied, three previously fire-affected areas and one control area. The result shows that prescribed forest fires influence the ground and field layer vegetation, and there were significant differences between the areas. The vegetation structure changed, and new conditions were created for subsequent successional processes. The effective number of species decreased after the fire but subsequently increased over time. The percentage of vegetation cover showed the same result with a rapid re-establishment rate, especially during the 6 following years. Biomass production reached the highest value 21 years after the fire, but showed a declining trend compared to the control area. There was no significant difference regarding soil pH, which was expected. There are many factors that may affect the short- and long-term effects of prescribed forest fires, such as fire intensity and the soil depth reached by the fire, but despite variations among the areas, some trends were found