Contradictions and continuities: a historical context to Euro-American settlement era fires of the Lake States, USA

Background The Lake States experienced unprecedented land use changes during Euro-American settlement including large, destructive fires. Forest changes were radical in this region and largely attributed to anomalous settlement era fires in slash (cumulation of tops and branches) following cutover logging. In this study, I place settlement era fires in a historical context by examining fire scar data in comparison to historical accounts and investigate fire-vegetation-climate relationships within a 400-year context. Results Settlement era fires (1851-1947) were less frequent than pre-settlement fires (1548-1850) with little evidence that slash impacted fire frequency or occurrence at site or ecoregion scales. Only one out of 25 sites had more frequent settlement era fires, and that site was a pine forest that had never been harvested. Settlement era fires were similar across disparate ecoregions and forest types including areas with very different land use history. Settlement fires tended to burn during significantly dry periods, the same conditions driving large fires for the past 400 years. The burned area in the October 8, 1871, Peshtigo Fire was comprised of mesic forests where fuels were always abundant and high-severity fires would be expected under the drought conditions in 1871. Furthermore, slash would not have been a major contributor to fire behavior or effects in the Peshtigo Fire when logging was still limited to relatively accessible pine forests. Conclusions Historical written accounts of fires and settlement era survey records provide a reference point for landscape changes but lack temporal depth to understand forest dynamics. Tree-ring analyses provide a longer (ca. 400 year) context and more mechanistic understanding of landscape dynamics. While settlement land use changes of Lake States forests were pervasive, fires were not the ultimate degrading factor, but rather likely one of the few natural processes still at work.

Automated summary

This study examines the historical context of settlement era fires and their relationship with fire-vegetation-climate within a 400-year context. The results show that settlement era fires were less frequent than pre-settlement fires, and slash did not impact fire frequency or occurrence significantly. Settlement fires burned during dry periods, similar to large fires in the past 400 years. Fires occurred across different ecoregions and forest types, and slash was not a major contributor to fire behavior or effects.