Climatic Controls of Wildfire in the Boreal Forest and Arctic Tundra Biomes across Multiple Spatial and Temporal Scales
Wednesday, 17 December 2014
Boreal forest and arctic tundra fire regimes are highly sensitive to climate. Thus, predicting fire regime response to future climate change requires understanding modern fire-climate relationships across a range of spatial and temporal scales. We quantified fire-climate relationships across the entire boreal forest and arctic tundra biomes using MODIS MCD64 area burned data spanning 2002-2012, observed climate data, and ecoregion classifications. Stratifying analyses in space (biome and ecoregion) and time (annual and decadal) allowed us to infer how variability in fuel moisture and vegetation type influenced area burned and fire occurrence across multiple scales. At annual time scales and the biome level, area burned was significantly correlated with summer temperature (rboreal = 0.37, rtundra = 0.28, p < 0.01) and precipitation (rboreal = ˗0.39, rtundra = ˗0.16, p < 0.01), consistent with results of past studies. Within ecoregions, fire-climate relationships varied considerably, potentially due to variations in dominant vegetation (e.g. Picea vs. Larix forests) or the limited temporal coverage of the area burned data. At decadal time scales, fire was moderately biased toward warmer regions of the boreal forest, further highlighting the importance of summer fuel moisture influencing boreal forest flammability. Tundra areas characterized by high summer temperatures and rainfall were more prone to fire activity than cool, dry regions, likely due to more abundant vegetation cover that facilitates fire spread. While fire-climate relationships were best resolved at the biome scale, predicting the local impacts of climate change requires analyses that account for the combined effects of climate and vegetation on burning. Future work will use statistical models to quantify these relationships across the spatial and temporal scales considered here, facilitating projections of fire activity for the 21st-century.