Fundamentals - Wildland Fuel Fundamentals and Applications - page 17

Fig. 2.2 The scaling of the
combustion process over time
and space from Moritz et al.
( 2005 )

replaced over time along pathways of disturbance adaptations, shade tolerance, and
biophysical processes; Chap. 6). Missing from this diagram are the key biophysical
processes that control fuels, namely deposition (fallen plant material often called
litterfall) and decomposition (Chap. 6). The interactions of plant succession and en-
dogenous and exogenous disturbances with biomass deposition and decomposition
mostly govern fuel properties, fuelbed dynamics, and spatial distributions at local
to landscape scales.
This brings up an interesting dilemma in that most fire behavior research has
been done at the fuelbed or flame scale (Sullivan 2009a ) often resulting in a scale
mismatch between fuel management and fire behavior, because most fuel manage-
ment issues demand a coarser scale of analysis (Keane et al. 2012a ). Therefore,
an overview of how fuels are defined in surface fire behavior models is needed to
understand the current and past use of fuels.

2.2 Surface Fire Behavior Modeling

2.2.1 Fire Behavior Formulation

The great fires of 1910 created the first real need for an understanding of fire be-
havior and search for models to predict fire behaviors (Pyne 2001 ). US fire pio-
neers, such as Gisborne ( 1927 ) and Hawley ( 1926 ), linked empirical evidence with
observed fire characteristics to explain the behavior of fire. Later, Curry and Fons
( 1938 ) and Fons ( 1946 ) attempted to describe fire spread using more theoretical,
physically based relationships. However, it quickly became evident to fire managers
that these physical relationships were too complex to easily apply on the fire line.
Fire managers needed some way to easily estimate fire behavior to more effectively
manage wildfires, predict effects of prescribed burns, and save firefighter's lives.