Turnover of beetle assemblages after a large scale wildfire in a boreal forest landscape

Fire is considered the most important natural disturbance in the boreal forest [1]. Fire suppression has made large-scale forest fires rare in the managed boreal landscape and caused a significant habitat loss for species dependent on stand replacing disturbance. Before the middle of the 17th century, lightning ignitions could explain the fire interval. During the 19th century the number of ignitions increased but the total burnt area decreased due to increased human activity combined with effective fire suppression. Fire suppression impacts all parts of this landscape, even large protected areas with limited human influence. Beetles are a very rich and diverse species group in the boreal forest and has been widely used in ecological research. The impact of long term fire suppression are hard to establish but Johansson, 2011 [2] suggests that the effects of large scale forest fires on beetle assemblages can be influenced by the management history of the landscape. To better understand the species turnover of beetles after a large natural fire in a landscape less impacted by modern forestry, we monitored beetles during three years after a >300 ha wildfire in Muddus national park. Muddus is the largest national park below the mountain range in Sweden, located in the northern boreal zone. We used 10 flight intercept traps on a transect through the burnt area. The area is dominated by old growth pine (Pinus sylvestris) forest and reoccurring fires has been recorded since the 15th century [3]. The beetles were divided into functional groups depending on substrate and nutrient preferences, red-list category as well as their dependency on fire. Species composition, abundance and species richness changed significantly between the tree years. There was a continuous turnover of species with unique species each year. The second year after fire was the most abundant and species rich. This pattern was most prominent for the saproxylic beetles, especially cambiovores, and predators. We found several red-listed and fire dependant species including the Cerambycidae; Acmaeops septentrionis. This study show that reintroduction of fire benefit pyrophilious species even after a century of landscape level fire suppression. Prescribed burning might have the potential to be more beneficial for biodiversity conservation management if allocated to areas with low human impact and unbroken fire history. 1. Zackrisson, O., Influence of Forest Fires on the North Swedish Boreal Forest. Nordic Society Oikos, 1977. 29(No. 1): p. 22-32. 2. Johansson, T., et al., Short-term responses of beetle assemblages to wildfire in a region with more than 100 years of fire suppression. Insect Conservation and Diversity, 2011. 4(2): p. 142-151. 3. Engelmark, O., Forest fires in the Muddus National Park (northern Sweden) during the past 600 years. Canadian Journal of Botany, 1984. 62(5): p. 893-898.peerReviewe