Canadian Forest Service Publications
The climate space of fire regimes in north-western North America. 2015. Whitman, E.; Batllori, E.; Parisien, M.-A.; Miller, C.; Coop, J.D.; Krawchuk, M.; Chong, G.W.; Haire, S.L. Journal of Biogeography 42(9):1736-1749.
Issued by: Northern Forestry Centre
Catalog ID: 36058
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Aim Studies of fire activity along environmental gradients have been undertaken, but the results of such studies have yet to be integrated with fire-regime analysis. We characterize fire-regime components along climate gradients and a gradient of human influence.
Location We focus on a climatically diverse region of north-western North America extending from northern British Columbia, Canada, to northern Utah and Colorado, USA.
Methods We used a multivariate framework to collapse 12 climatic variables into two major climate gradients and binned them into 73 discrete climate domains. We examined variation in fire-regime components (frequency, size, severity, seasonality and cause) across climate domains. Fire-regime attributes were compiled from existing databases and Landsat imagery for 1897 large fires. Relationships among the fire-regime components, climate gradients and human influence were examined through bivariate regressions. The unique contribution of human influence was also assessed.
Results A primary climate gradient of temperature and summer precipitation and a secondary gradient of continentality and winter precipitation in the study area were identified. Fire occupied a distinct central region of such climate space, within which fire-regime components varied considerably. We identified significant interrelations between fire-regime components of fire size, frequency, burn severity and cause. The influence of humans was apparent in patterns of burn severity and ignition cause.
Main conclusions Wildfire activity is highest where thermal and moisture gradients converge to promote fuel production, flammability and ignitions. Having linked fire-regime components to large-scale climate gradients, we show that fire regimes – like the climate that controls them – are a part of a continuum, expanding on models of varying constraints on fire activity. The observed relationships between fire-regime components, together with the distinct role of climatic and human influences, generate variation in biotic communities. Thus, future changes to climate may lead to ecological changes through altered fire regimes.
Plain Language Summary
“Fire regimes” describe the type of wildfires in a specific area (how often they occur, their typical size, etc.). This study provides a new way of looking at fire regimes. The researchers defined distinct climate zones in a large area of western North America (from northern British Columbia to northern Utah and Colorado) according to climate factors of temperature and of moisture. They identified climate zones where fires had occurred between the years 1984 and 2011, as well as those climate zones where fire was absent. Fire activity was highest where there were intermediate levels of both temperature and moisture, whereas it was lowest in zones of climate extremes. For example, areas that are too wet are not conducive to burning, whereas areas that are too dry (such as deserts) have insufficient vegetation for burning. Aspects of the fire regime, such as fire size and severity, varied across climate zones and were significantly related to one another. Differences in the fire regime also resulted from human influences. This framework can be used to help understand and predict wildfires in any-fire prone region. As well, it can be used to help predict changes in fire regimes as climate changes.