Environmental Plant Responses and Wildland Fire Danger

Abstract

Fuel moisture is one of the key drivers of fire danger. Fuel moisture limits combustion during the preheating phase, as water needs to be evaporated before the fuel can ignite. Some proxies for fuel moisture have been commonly used, like the Fire Weather Index (FWI) or some of its components, but the success of these proxies has been mixed. It is thus advantageous to incorporate more biological realism to predicting changes in fuel moisture. Dead fine fuel moisture may be modeled, at daily scales, from vapor pressure deficit. Live fuel moisture content is driven by water potential, which is more difficult to forecast at regional scales. It is also possible to obtain remotely sensed estimates of fuel moisture, but only predictive models of fuel moisture allow forecasting. Measuring and modeling fuel moisture are not trivial as different aspects, including variations in live/dead ratio over the fire season, influence the response. Leaf senescence may indeed lead to large changes in crown fire likelihood. Although low moisture is a requirement for fire activity, assuming that lower fuel moisture automatically translates into higher fire danger or activity may not be correct under some circumstances, as other processes including atmospheric conditions may play a similar or even larger role.