Near-natural forests in southern Sweden

Timber production and protection of biodiversity are two main issues in south Swedish forestry. This thesis explores the possibilities of combining the two issues in a nature-based silviculture. Different branches of science, palaeoecology, silviculture and forest vegetation ecology, were combined to give a multidisciplinary approach to the subject. Mimicking the historical forest composition and processes in the silvicultural measures for the benefit of both biodiversity protection and timber production was identified as one possible way of developing a nature-based silviculture. The long period of human influence on the landscape in southern Sweden has effectively removed all the remnants of natural forest that could have been used as references in the mimicking procedure. Consequently, historical references were searched. A method to describe former forest conditions was developed using palaeoecological data and methods. It was found that the historical deciduous dominance was pronounced. Over 2000 years southern Sweden has been transformed from a deciduous to a coniferous landscape. Human activities were shown to be a major driving force in this change. Several detected historical forest types were possible as references for the mimicking approach, but forest types common in the past and rare today were suggested for maximal efficiency in obtaining high biodiversity. Mixed nemoral deciduous forests were pointed out as a historically widespread forest type with very little resemblance in the present landscape. The small fragments left are important for present biodiversity and from many other aspects. Development of a nature-based silvicultural system for the management of mixed nemoral forest stands based on the theory of mimicking was begun. A silvicultural experiment was established in a near-natural, mixed nemoral forest stand in southern Sweden and the early effects of the silvicuitural treatments tested were evaluated with regard to floristic diversity. The early findings indicate that advance growth may be an effective source for regeneration of the forest type. Soil scarification is not recommended when regenerating mixed nemoral deciduous forest stands as the destruction of advance saplings was not compensated by new establishment, and because a tendency towards alteration of the ground flora typical of nemoral forest to a pioneer plant community was traced. Sparse shelterwood cutting is suggested as an appropriate way of combining biodiversity consideration and timber production in mixed nemoral deciduous forest stands. Finally, a framework of an approach to obtain a nature-based silvicultural system was developed, based on the presented results and other informatio