Quantifying influences and relative importance of fire weather, topography, and vegetation on fire size and fire severity in a Chinese boreal forest landscape

• We compared landscape controls of fire size and fire severity.
• Fire weather exerted strong influences on fire size.
• Vegetation is the dominating control of fire severity.
• Driving mechanisms of these two attributes possess different scale dependence.
• Fire size and fire severity may have inconsistent responses to climate warming.

Fire size and fire severity are two crucial parameters for describing fire regimes that reflect spatial heterogeneities of fire spread behavior and its interaction with the environment. Determining how environmental controls regulate these two metrics of the fire regime is of critical importance for predicting response of fire to climate change and designing strategic fire management plans. Here, we evaluated influences and relative contributions of fire weather, topography, and vegetation on fire size and fire severity in a Chinese boreal forest ecosystem. We also compared how relative contributions vary along a continuous gradient of spatial scales using a moving-window resampling approach. Results showed fire weather was the dominant driving factor for fire size, while vegetation and topography exerted stronger influences on fire severity. Such relative influences on fire size and fire severity possessed different scale dependence. For fire size, small burns (<130 ha) were mainly constrained by vegetation as it accounted for nearly 43% relative importance, but larger burns (>200 ha) were more strongly influenced by extreme fire weather conditions, which accounted for more than 50% relative importance. In contrast, the relative importance of fire weather on fire severity was always less than 20% across the entire range of spatial scales, while relative contributions of vegetation were relatively stable and always greater than 45%. Our study suggests that fuel treatments may have little effect on reducing fire size in boreal forests, but may function to mitigate the severity of future fires. Vegetation type and terrain conditions are important factors to consider for improving efficiency of fuel management.