Multi‐millennial fire frequency and tree abundance differ between xeric and mesic boreal forests in centralCanada

Abstract

Summary Macroscopic sedimentary charcoal and plant macroremains from two lakes, 50 km apart, in north‐western Ontario, Canada, were analysed to investigate fire frequency and tree abundance in the central boreal forest. These records were used to examine the controls over the long‐term fire regime, and vegetative dynamics associated with fire return intervals (FRIs). There were 52 fire events at Lake Ben (surrounded by a xeric landscape) between 10 174 calibrated years before present (cal. year bp) and the present with an average FRI of 186 years with values oscillating between 40 and 820 years. Forty‐three fire events were recorded at Lake Small (surrounded by a mesic landscape) between 9972 cal. year bp and the present with an average FRI of 229 years and a range of 60–660 years. FRIs at Lake Small decreased significantly after c. 4500 cal. year bp, whereas at Lake Ben FRIs remained similar throughout the Holocene. Different FRI distributions and independence in the occurrence of fire events were detected between 10 000 and 4500 cal. year bp for the two sites. Between 4500 cal. year bp and the present, similar FRIs were observed, but fires continued to occur independently. Longer FRIs resulted in declining abundance of Larix laricina in both landscapes. Longer FRIs resulted in a decline in the abundance of Picea mariana in the xeric landscape, but a marginal increase in the mesic landscape. Abundances of Pinus banksiana, Pinus strobus and Betula papyrifera were unrelated to FRI, underlying that these species maintain their local abundance irrespective of fire frequency. Synthesis. Our results show contrasting fire regime dynamics between a xeric and mesic landscape in central boreal forests, Canada. These results highlight the influence of local factors as important drivers of fire frequency at centennial to millennial scales. Local site factors, especially soil moisture, need to be incorporated into predictive models of vegetation response to climate change.

Linking resource availability and heterogeneity to understorey species diversity through succession in boreal forest of Canada

“…Gray and Aster macrophyllus L. (Hart & Chen, ). Wildfire is the most common natural disturbance agent in the study area, with site‐specific fire return intervals ranging from 40 to 820 years (Senici et al., ), and an average fire return interval of approximately 100 years for the past century (Senici, Chen, Bergeron, & Cyr, ).…”

Effects of coarse woody debris on plant and lichen species composition in boreal forests

“…Wildfire is the most common natural disturbance agent in the study area, with site‐specific fire‐return intervals ranging from 40 to 820 yr (Senici et al. ), and an average fire return interval of approximately 100 yr for the past century (Senici et al. ).…”

Strong Gradients in Forest Sensitivity to Climate Change Revealed by Dynamics of Forest Fire Cycles in the Post Little Ice Age Era

“…In Eastern North America, the length of the fire cycle, which is the time required to burn the equivalent of a specified area, has been shown to have an important control on regional vegetation cover dynamics. The fire cycle shapes the northern distribution limits of canopy dominants (Senici et al, ) and defines successional pathways (McIntire et al, ). Ultimately, fire cycle variability controls the transitions between temperate and boreal forests (Bergeron et al, ) and from closed to open canopy boreal forests (Blarquez et al, ; Gauthier et al ).…”