Climate Change, Wildfire, and Landscape Homogenization in Western Canada

English Abstract:

Wildfire is the most important disturbance agent in forests of Western Canada, affecting stand structure and composition, biodiversity, biogeochemical cycling, hydrologic processes, and natural resource extraction. Despite considerable research, consensus on the frequency and severity of historical fire occurrence has been elusive in much of the Canadian Cordillera. Much of this uncertainty derives from methodological limitations. One area of particular contention has focused on the degree to which surface versus crown fires were historically important; a second relates to how disproportionately effective suppression of surface fires may have homogenized the landscape and altered the modern and future fire regimes. We have endeavored to overcome these uncertainties by employing a multiproxy approach to reconstructing fire history, and by using randomized site and sample selection. Drawing from a network of fire scar and tree cohort samples throughout western Canada we show that mixed severity fire was historically more frequent. We further show that in some forests the fire season has shifted significantly, and forests have become more homogenous. These findings have import ant implications for land management strategies that aim to restore historical conditions, or aim to mimic the natural disturbance regime.