Interactions among climate, fuels, hydrology, and fire in landscapes of the western US

Background/Question/Methods

Fire and water are linked across multiple spatial and temporal scales.  Climate provides a top-down control on fire regimes via seasonal-to-multidecadal patterns of temperature and precipitation and their interaction.  At fine scales, fuel structure and composition interact with micro-meteorology to affect fire intensity and fire spread. At all scales, water balance, specifically the interaction between potential and actual evapotranspiration, provide the physical basis for understanding the short-term climatic controls the spatial variability in fuel availability and the landscape patterns it produces. We use area burned between 1980 and 2006 in ecosections of western North America to explore whether a generalized relationship between climate and wildfire based on water balance exists.

Results/Conclusions

Water balance - fire relationships vary with vegetation  (fuel) type, but are strong in most forested systems. Antecedent precipitation is a better explanatory variable in non-forested systems. We provide an empirical analysis of the relationships between the area burned by fire and plant-relevant hydrologic variables including water balance deficit and show how these relationships vary with ecosystem geography and fuel type. This analysis provides a quantitative physical climate and ecohydrological basis for modeling the relationship between climate and wildfire.