Résumé - CAFD

The effects of forest fuel connectivity on spatiotemporal dynamics of Holocene fire regimes in the central boreal forest of North America.

Dominic Senici, Han Chen, Yves Bergeron, Adam Ali.

Understanding fire regime dynamics is central to predicting forest structure and the compositional dynamics of boreal forests. Spatial and temporal variations in fire frequency in central Canadian boreal forests over the last 10 000 years were examined to evaluate the influence of bottom-up controls on the regional fire regime. We analysed macroscopic charcoal larger than 160??m from sediment cores from six lakes to reconstruct fire history and performed GIS analysis of regional landscape features to investigate how fire frequency has changed temporally and how non-climatic factors may have affected long-term fire frequency. Our generalized linear mixed model revealed that temporal changes in fire return intervals (FRIs) were highly dependent on landscape connectivity as inferred through the abundance of natural firebreaks in the form of open water lakes and wetlands. FRIs did not change significantly among highly connected landscapes throughout the Holocene; in contrast, FRIs were significantly longer among poorly connected landscapes in the early Holocene (10–5 cal ka BP), suggesting that the abundant regional firebreaks limited fire spread. All sites had similar FRIs in the late Holocene. The diminishing influence of firebreaks suggests that the regional climate during the late Holocene has overshadowed the influences of the bottom-up controls on fire activities.