Impacts of fragmentation on boreal forests in a natural landscape, northern Sweden

Background/Question/Methods

We examined the influence of landscape structure on disturbance, succession, and the duration of legacies initiated by fire across a naturally fragmented boreal forest in northern Sweden. We inventoried 2,038 trees, of which 1,249 were cored and dated, and collected 128 soil samples on 16 distinct forested islands.  The landscape is naturally fragmented with spruce forest fragmented by mire.  Island size ranges from 0.17ha to 8.88ha.  In Sweden there are 87,298 Woodland Key Habitats that cover 410,150ha, 85% of these are between 0–10 ha in size indicating over 74,000 reserves are directly comparable to our results.  Sweden is not the only location where fragmentation has occurred through naturally or anthropogenic processes.  This study explores the effects of fragmentation on boreal forest ecosystems.

Results/Conclusions

Several stand characteristics were significantly correlated with island size, including density, basal area increment, the importance of Betula, the importance of Picea, forest composition. There is difference in age structure between large and small islands. Island size additionally effects the climate relationship for the forest.  Soil charcoal was found in 76 of 128 samples and on all but one island. Charcoal mass showed no consistent relationship with island area, isolation, or any stand variables. One of the islands had fire in its recent history, the structure, composition, and climate response is significantly different compared to the other islands. Our findings indicate landscape structure as a fundamentally important driver of forest structure in this landscape and provide a frame for understanding the length of fire’s ecological legacy in boreal forests.