Historical drivers of a frequent fire regime in the red pine forests of Voyageurs National Park, MN, USA

We developed a fire history for Voyageurs National Park (VNP), MN, USA based on 129 fire-scarred cross sections collected at 39 disjunct locations to develop a baseline understanding of the history of fire in the region. We dated 443 scars representing 126 unique fire years with the earliest fire recorded in 1665 and the most recent in 1972. The Weibull Median Fire Interval from individual fire intervals at the 39 sites is about 18 years and two years for the study area as a whole. Site-scale fire intervals were relatively short, with about 75% of the intervals between fires less than 30 years and more than half of the intervals shorter than 20 years. Approximately 61% of the 126 unique fire years were recorded at only 1 site and about 20% of fires were recorded at 2 or more sites. The median interval between fires that were synchronous at 3 or more sites is 7 years, with the earliest synchronous fire occurring in 1718 and the last in 1936. Fires occurring at more than three sites coincided with summers that are significantly drier than average during the fire year. In VNP, several lines of evidence are suggestive of the potential role of people in augmenting the fire regime above that which would have occurred due to lightning alone. The patterns of fire activity in VNP highlight the same issues that have been noted elsewhere, namely that fires have been prominent in the past in shaping the character of Upper Great Lakes forests and that fire activity has been much reduced since the 20th century. The reduction of fire activity observed after the early 20th century could be as much related to the reduction of human ignition and the removal of people from the landscape as it is to active suppression. This research suggests that the appropriate use of planned fire should be employed as an important management tool, likely through the intentional ignition of fires rather than a reliance on lightning starts alone. This research represents another step in better understanding the processes that have shaped the landscape of Voyageurs National Park, while continuing a dialogue around the future of an ecologically, economically, and culturally significant subset of the Border Lakes landscape.