Vegetation dynamics and disturbance history in three deciduous forests in boreal Sweden

Remaining deciduous forests in the Fennoscandian boreal landscape have high ecological value, and are considered as key components of the forest landscape as well as remnants of a former natural forest type. To improve our understanding of the formation of deciduous forests, we studied past disturbance regimes and vegetation dynamics in three deciduous forests in boreal Sweden using dendro-ecology, pollen analysis and charcoal analysis. We identified three stages in the development of the studied stands. Firstly, the coniferous period (pre 1800), a long-lasting period characterized by frequent fires, livestock grazing and extensive agriculture during which Pinus sylvestris was dominant. Secondly, the transformation period (1800 - 1900), when logging removed most pines from the sites while fire and grazing continued. At the time of the last fire, the sites lacked a local seed source of pines, resulting in a post-fire succession dominated by deciduous species with the capacity to disperse over long distances. Thirdly, the deciduous period (1900 - present), with little or no disturbance from fire, grazing or logging. Thus, the present deciduous stands have their origins in a complex interaction between changes in fire regime, extensive land use patterns and logging, contrary to earlier simplified explanations. We conclude that the complexity of historical patterns of land use, vegetation dynamics and disturbance should be acknowledged in the future when selecting areas for nature conservation and developing models for ecologically oriented forestry.