<p>What is located on the bottom in the water outside of Birka? Remains of a water palisade or jetties and other constructions.</p><p>Birka a Viking Age town that existed between AD 750 and 975 was located on the northwestern part of the small island of Björkö, in the Mälar archipelago of the Baltic Sea in Sweden. The Town was protected onshore by a hill fort and a town rampart. It is a widely spread assumption that Birka had a water palisade as a part of its<strong> </strong>defense. There are logs and other remnants on the bottom of the lake dating back to the Viking age. Uncertainty remains as to the origin of these remnants. The questions being, are they from a water palisade or the remnants of jetties and other constructions. The amount of fire wood alone needed to support 500 inhabitants for one year is equal to a wall of wood one meter high, one meter wide and two kilometers in length. This calculation does not take into account the wood used for transportation of other materials, people and animals. The conclusion is that future examination of the area is necessary to find out what is located on the bottom in the water.</p>

What is located on the bottom in the water outside of Birka? Remains of a water palisade or jetties and other constructions. Birka a Viking Age town that existed between AD 750 and 975 was located on the northwestern part of the small island of Björkö, in the Mälar archipelago of the Baltic Sea in Sweden. The Town was protected onshore by a hill fort and a town rampart. It is a widely spread assumption that Birka had a water palisade as a part of its defense. There are logs and other remnants on the bottom of the lake dating back to the Viking age. Uncertainty remains as to the origin of these remnants. The questions being, are they from a water palisade or the remnants of jetties and other constructions. The amount of fire wood alone needed to support 500 inhabitants for one year is equal to a wall of wood one meter high, one meter wide and two kilometers in length. This calculation does not take into account the wood used for transportation of other materials, people and animals. The conclusion is that future examination of the area is necessary to find out what is located on the bottom in the water.

Sustainable use of species-rich moist forests is hampered by an insufficient understanding of their dynamics and long-term response to different wood harvesting strategies. This thesis contributes to a better understanding of natural forest dynamics, explores the productivity of native forests subjected to different management strategies, and quantifies the ecological impacts of these strategies. The thesis focuses on two study regions: tropical montane cloud forest (TMCF) in central Veracruz, Mexico, and Valdivian temperate rain forest (VTRF) in northern Chiloé Island, Chile. The process-based forest growth model FORMIND is applied to study natural forest succession, to assess long-term ecological implications of fuelwood extraction on TMCF, to explore the potential of secondary TMCF for provision of ecosystem services and fuelwood, and to compare potential harvesting strategies for VTRF regarding forest productivity and ecological consequences.Simulation results show that both forest types have a high potential for wood production. As wood extraction increases, the forest structure becomes simplified because large old trees disappear from the forest. The species composition shifts to tree species that are favoured by the respective harvesting strategy. The overall ecological impact increases linearly with the amount of extracted wood. Simulation results allow to define management strategies that balance conservation and production objectives, promote the regeneration of desired tree species, or minimise shifts in the species composition of the forest. Process-based forest models enhance our understanding of the dynamics of species-rich moist forests and are indispensable tools to assess long-term implications of anthropogenic disturbances on forest ecosystems. Thereby they contribute to the conservation and sustainable use of native forests outside protected areas.