Fuel Concepts - Wildland Fuel Fundamentals and Applications - page 174

Obviously, the best fuel treatment option for both reducing fuels and restoring
fire-prone ecosystems is fire implemented as prescribed burns or controlled wild-
fires (allowing wildfires to burn). Fire has shaped past landscapes so it can best
be used tomorrow for restoring the fire-excluded ecosystems of today. It performs
many attractive actions such as (1) reducing canopy fuels by killing fire-susceptible
trees and dense regeneration, (2) creating heterogeneous patches and landscapes,
(3) consuming fuels, (4) facilitating nutrient and water cycling, and (5) favoring
fire-adapted vegetation leading to more resilient landscapes. The dilemma facing
most fire managers, however, is how to reintroduce fire into areas that now have
such great buildups of canopy and surface fuels that any fire may kill large trees
and cause uncharacteristically high plant mortality. Burning fire-excluded areas with
prescribed fire is difficult because weather conditions that are needed to achieve
targeted fire intensities may be rare and the risk of damaging ecosystems, burning
property, or harming people may be great. The successful reintroduction of fire will
take multiple treatments staggered in time. In the first entry, mechanical treatments
may be needed to reduce canopy fuels so that fire treatments can follow to consume
surface fuels and lower residual tree regeneration without high tree mortality (North
et al. 2012 ). Further, it will take several entries into treated stands over time to obtain
the stand structures that will be resilient in the face of climate change and resistant
to future disturbance events. Some estimate it will take three to seven burns to return
landscapes to a semblance of the historic past. Irrespective of treatment strategy,
wildfires will eventually burn most areas regardless of the level of fire suppression
so designing effective treatment regimes that protect and restore ecosystems while
reducing fuels will need to balance society's tolerance for fire with an ecosystems'
ability to accumulate fuels using enlightened fire management that fully integrates
mechanical treatments and prescribed fire with the eventual wildfires.

10.2.3 Fuel Treatment Longevity

Treatment longevity depends on the highly variable fire and fuel characteristics be-
ing used to evaluate it and has little meaning without considering space and time.
Since most fuel treatments are costly, it is important to know how long they will
last before another one is needed. The time over which fuel treatments are effec-
tive is often called treatment longevity . Longevity is important for planning and
scheduling future fuel treatments, but, similar to flammability, assessing treatment
longevity is difficult because of the temporal and spatial complexities of fuelbed
dynamics. The wide ranges of measurements that can be used to assess longevity
coupled with the incredible variability and complexity of fuelbeds as they interact
with the biophysical environment make estimating longevity nearly impossible.
The most important challenge in quantifying longevity is deciding which suite of
fire and fuel variables to use to assess how long treatments are effective. An objec-
tive of a fuel treatment, for example, might be to reduce surface fuel loadings or
decrease CBD below a threshold value, or to create fuelbed conditions, that when